Processing Filings and Pieces of Gold Mixed With Minor Amounts of Silver

The material received for processing normally will be a mixture of filings, bits and pieces of gold, such as crowns, sizing pieces and old jewelry, along with occasional dental gold and usually some silver. The case we will deal with here is where one hasn't received a great deal of silver. Lots received that contain mostly silver and some gold will be handled similarly. We will deal with that situation elsewhere in this document. Examine the material to see what it contains, but don't spend a great deal of time on it. Simply get a general idea what you are processing.

Incinerating the Waste

Having briefly looked at the material, place it in a stainless steel frying pan and incinerate it on the hot plate in the hood. Burn it very well, at the end heating it with the torch until all combustion has ceased and the glowing bits have burned out. Be careful not to melt the gold. When heating the outside of the pan, take care to not get it too hot. The filings will adhere to the pan, or a hole will be burned through the pan if you don't keep the torch moving. One can check the lot to see if everything has been incinerated by playing oxygen from the torch on the super heated surface of the filings. Any combustible material will glow a bright orange to yellow.

Screening

After cooling, screen the entire lot, then remove any magnetic particles with the small magnet from the material sitting on the top sieve. The metal removed with the magnet should be placed in the mortar and rubbed well, then remove anything the magnet will pick up from the mortar and place it in the bucket ((stock pot).- see stock pot in Hoke's book for a better understanding of this) so that any traces of values will be recovered rather than discarded. The material left in the mortar has value, and should go back in the lot of material being screened. Place anything that is in the first sieve in the mortar and rub it well, then screen the entire lot again. At this point any small particles that had adhered to the larger pieces should have been knocked off and gone through the sieve. If so, remove the larger pieces, placing them in a small container (cottage cheese cups work great and are easily incinerated when it is time to dispose of them). Repeat the mortar treatment until such time that only coarse metallic pieces remain. Any non-metallic large pieces (bits of melting dishes, small rocks, broken stones, other than diamond) should have been removed and placed in the storage container that you will maintain to dispose of such things as old asbestos, old clay melting dishes, broken beakers that are contaminated with gold and silver, and any thing non-metallic that has value that will eventually be run in the ball mill.

DO NOT PLACE GRAPHITE CRUCIBLES IN THIS CONTAINER. THEY SHOULD BE PICKED CLEAN MANUALLY AND DISCARDED.

In the process of screening, watch for diamonds. Remove anything that looks like the gem stone, even broken pieces. Small bits of diamond will bring $25 per carat.

Silver

If a fair amount of silver is found in the lot, it should be removed and weighed for settlement. Regal Refining has had a policy of no return on anything under 1/2 ounce troy. It is a good idea to remove any silver that is found and use it for inquartation. One can easily add too much silver to a lot when it is inquarted if the lot received contains a great deal of silver and an allowance for it is not made when inquarting. While a little too much silver may do no harm, when the amount becomes excessive, the gold has a tendency to disintegrate when the lot is being dissolved in nitric, and much more time is spent waiting for the fine particles to settle so they won't be poured off with the spent acid.

Testing White Metals

If there is a question about what a white metal is, it should be tested with silver testing solution. The orange colored testing solution is a mixture of potassium dichromate, nitric acid and water. Using the glass dobber in the testing solution bottle, apply a drop of solution to the piece in question. The solution will turn blood red if it is silver. There is no reaction on white gold or aluminum. If a piece of nickel is tested, given enough time the spot tested will turn green. A similar test with nitric

acid will be much faster, and the same green to blue/green color will be found if the metal is nickel. If there is still a question about what you have after testing for the platinum group, aluminum, and stainless steel, run the unknown piece. Stainless will give somewhat similar colors that palladium does when it is heated, but it will turn black when it cools after it has been over heated. A file is also a good test for stainless. It is a rather hard to file metal. It will float a somewhat dull file rather than cut when the file is applied. Its characteristics are more of a tough metal rather than a hard one. Not all stainless steel is magnetic, so the magnet alone isn't a good test.

Platinum and Palladium

A test with the torch will distinguish platinum. Platinum melts at about 3300 degrees Fahrenheit. The piece will turn white hot and not melt, though at that point it isn't far from doing so. Platinum remains without any oxides after heating. It will be at least as shiny as it was before the torch was applied. Palladium, if it is tested with the torch, will have rainbow colors (pink, green, blue) and some grey when it cools. The colors are the result of oxidation. It melts about 500 degrees lower than platinum, so it will melt before it gets white hot. Any pieces of platinum or palladium should be removed. Weigh the platinum for settlement and store it in your platinum container. Regal Refining has allowed 75% in gold for platinum in the past. You may care to change that, but I think it is fair, considering the penalties when selling to the major refiners. Palladium has never had any value for the customer when submitted to Regal Refining. It too should be stored for future sale.

Aluminum

Any aluminum that is found should be removed and placed in the bucket (stock pot). Aluminum works very well in recovering trace values and any values that are stuck to it are not lost that way. DO YOUR BEST TO KEEP ALUMINUM OUT OF THE BATCHES OF GOLD THAT ARE PROCESSED. IT CREATES FILTRATION PROBLEMS, AS DOES LEAD AND TIN. Discard any lead or tin you may find. (Tin, not sheet steel, which most people call tin). Aluminum foil and aluminum bottle caps and pieces of them are found frequently. Aluminum does not dissolve in nitric acid, but does so almost violently in HCL. A good test for it is to drop it. Aluminum has a very light sound to it when dropped on a hard surface. Try dropping some known aluminum, then other metals to hear the difference. It works surprisingly well as a test. Its light weight will also give it away.

After all the metal on the first screen is finished, remove the top sieve and run the magnet through the filings sitting on top of the second screen. Rub the magnetic metal in the mortar then remove the magnetic bits with the magnet and discard them in the bucket (stock pot), as you did with the top sieve. Dump the contents of the screen in the mortar and rub well until everything that will break down has done so and gone through the screen. Again, watch for diamonds. The first sieve allows small diamonds to pass, but the second one will catch virtually all of them that do.

When all has gone through the screen that can, place what hasn't in with the larger pieces that came from the first screen. They will be weighed and silver added for melting.

Remove the bottom sieve and run the magnet through the filings in the bucket, placing anything that comes out into the mortar. After you have removed the metallic particles from the filings, rub them well in the mortar, then remove the metallic particles with the magnet, placing them in the stock pot. The filings are now ready to be processed with nitric acid to remove base metal and silver.

Processing the Filings

Pick a beaker that is somewhat small, record the beaker number on the process sheet and place the filings into the beaker. Wash down the beaker with the wash bottle to get all the filings in the bottom of the beaker, making sure you have the filings covered with water when you are done. SLOWLY add a little nitric acid to the beaker. You will get a very fast reaction if the filings have a lot of silver in them, and the solution can boil over, so allow the acid to work a few seconds before dumping in much. You will want to use enough acid to dissolve the base metals and silver, but not much more. Unfortunately, there isn't a formula for this, so use enough acid to perhaps double the amount of water you used to cover the filings. When you know that the beaker isn't going to boil over, place a watch glass on it and put the beaker on a burner with an asbestos pad. Allow the beaker to boil for quite a while, stirring it occasionally so the filings don't cook to the bottom. Boil until the solution you

have started with has evaporated down some. Using the nitric acid dropping bottle, add a few drops of nitric acid to see if there is any further action. You normally will find that after this operation not much happens when more acid is added. If there is no further action, slowly add some water to the beaker, stirring with a glass rod as you do. The solution will be quite hot, above the boiling point of water. You must stir and slowly add the water to avoid breaking the beaker, to avoid the heated acid solution from flashing the water to steam, and also to keep the solution from cooling before the water can dilute it. It tends to go hard as a rock when it cools if it hasn't been diluted. Once under boiling temperature, add a large amount of water to the beaker and stir, mixing the water well with the solution. Allow the beaker to stand until the flocculence has settled. The idea is to pour the solution on the copper bars to extract the silver and any palladium that has gone into solution, leaving the filings in the beaker. One normally doesn't find any platinum in this operation. Add water and pour off after settling at least a couple times. You want the solution coming from the beaker to be clear of color when you add the filings to the beaker containing the gold mud that has come from the processed solid pieces.

Inquartation

Your goal in inquartation is to get the gold to 6 karat, or 25% gold content so nitric acid can dissolve all the metals we are trying to remove from the gold. The base metals and silver are protected by the gold when it is above 35%, making the base metal removal almost impossible, and dissolving the gold is impossible, as the resident silver protects the gold against aqua regia. One can normally add 110% of the starting weight in silver to the pieces that are to be melted. If a good deal of dental gold is present, things change, as they do if the lot is 10K (theoretically 41% gold) material. Adjust the percentage accordingly. This is not a critical operation. The gold will process at 35%, but it will take much more time. The beaker must be allowed to boil extensively at 35% gold content. At a lower percentage, (less than 25%) the gold has a tendency to break into small particles and pour off with the dissolved copper, silver, nickel and zinc, so try not to go much below 25%. A lot of time is lost waiting for the solution to settle when it breaks up in this manner.

Dental Gold

As dental gold on the average will run about 68% in gold, one must add much more silver to process it. It is normally safe to add 200% of the starting weight in silver to dental gold to achieve a ratio that will dissolve in nitric acid.

Melting the Metal

When you have the material ready to melt, assign a beaker number to the lot and write it on the process sheet that you will use to track the metal. In choosing a beaker, pick one that will end up with no more than three ounces troy of pure gold. You will have to estimate what you think will come from the lot. Remember that you tried to get gold to 6K, so if you divide the gross weight by four (4), you will be close to the yield, though you should never make an estimate of yield for a customer in this way. It is simply your way of making process decisions. Keep your beakers as small as the metal will allow, as when you are quite busy, there isn't enough space for beakers, and using large ones simply takes up unnecessary space.

Set up the stainless steel tub that you pour your metal into, the melting tray, and place the metal to be melted into a melting dish. The metal is made up of the gold waste pieces removed from the screened lot along with the silver you added to inquart the gold. Use a rather violent flame in setting your melting torch. Your objective is to get the metal melted and mixed in order to pour it into the stainless tub which by now is full of cold tap water. If you play the torch well about the outside edge of the melted metal, it will be unnecessary to stir it. If the metal is too voluminous to stir with the torch, stir it with a carbon rod. When the metal is quite fluid, using the wheel weight plier, pour the lot into the stainless tub with a rather quick motion, keeping a steady stream of metal coming from the melting dish. Be careful not to crush the dish with the tool. Move about the entire water surface as you pour so you don't build a mound in the bottom of the tub.

Dissolving the Base Metals and Silver

Pour off the water and get the metal from the stainless tub into your beaker. Place some of the melted lot into the beaker by hand, being careful not to break it. Once a bed of melted metal is in the bottom, the balance of the metal in the tub can be washed into the beaker using a syringe and water.

Pour off the excessive water from the beaker after you have the melted metal in it. You will want to leave about a half inch of water over the metal. Add to the water about twice that much nitric acid. If there is enough water present, the lot will not boil over. Place the beaker on the hot plate with an asbestos pad under it and the burner lit. Use a high flame for this operation, as the hotter things are, the faster your work will go. The beaker should be covered with a watch glass so nothing is lost to evaporation. Keep an eye on it at first, and should it start to boil over, add more water to dilute the acid and cool the solution, slowing down the action. Normally once that has been done the lot can be left to dissolve without much attention. Allow the nitric acid to work on the metal until it quits working. You will notice an absence of the brown fume that comes from the nitric acid when it is actively dissolving the metal. At that point, add enough tap water to double the volume in the beaker and pour off the solution into the bucket containing copper bars. You will recover the silver in this operation, along with any platinum group metal that will be in solution. If enough acid has been used in the first operation, the metal in the beaker will now have a brown color, and will easily break into powder when pinched between your gloved fingers. You normally won't be to that stage after the first lot of nitric acid, however. If the metal is a light brass color, add more water and nitric acid and heat again. Repeat these operations until the gold has been freed from all base metal and silver. If the material melted is quite dirty, it is normal for the gold remaining to be in fine powder rather than staying in lumps as it was poured. The gold may even be black in color, and not settle well. Allow the solution to settle before pouring off when this happens, as the black in suspension is gold. It is a good idea as you come to the end of this operation to not pour on too much nitric acid. Use what you think will be enough and allow it to do all of its work, as any nitric acid you use in this operation that doesn't get used up will dissolve the copper bars, wasting the copper and filling your lab with brown fumes. It can get quite messy.

The acid solution that comes from dental gold will always contain platinum or palladium in solution, or both. The solution will have a green color to it. The platinum group will follow the silver and be recovered with it. You won't get it back until you part the silver in the silver cell. If you are curious about the content of the solution, test it with the testing solution "A" that Hoke talks about in the book. Before putting the testing solution on the sample drop, put a drop of HCL to precipitate the silver as chloride, as it gives a false reading if it is still in solution. Platinum will give you an orange to coffee brown reaction. Palladium will give you a number of different reactions, all of which are quite dark. The reaction will range anywhere from blue to green to brown. Many times it will resemble the reaction of gold, but no purple stain will be found in the spot plate when it is rinsed. If you aren't sure if you have palladium, it can be tested with DMG (Dimethylglyoxime). It will give you a canary yellow precipitate when it reacts with palladium. There is no reaction on platinum with DMG.

Dissolving the Filings and Gold Mud With Aqua Regia

Place the filings in the same beaker as the brown gold mud, and add one (1) ounce nitric acid and four (4) ounces HCL for each ounce of gold that you estimate is to be recovered. Filings will actually use more acid than the brown mud as they still contain traces of base metals. Add the acid slowly to avoid the beaker boiling over. The idea is to add a small amount of the acid mixture (aqua regia) and let it work, then add more. If all is added at once, the filings and fine gold powder go into solution immediately, with a sure boil over. The beaker should be placed on the burner and allowed to boil at a low heat until all the acid is used up or all the metal is dissolved. Don't use any more nitric acid than you need, as it must all be used up before the gold can be recovered by precipitation. An excess of HCL does no harm, and insures all the nitric that is able to be used up is used up as it reacts with the gold.

Evaporating the Gold Solution

Once all the acid is used up, or the gold is totally dissolved, take off the watch glass, pour in a little HCL to cool the solution, then pour in a few drops of sulfuric acid. Be sure to stir with the glass rod all the time the sulfuric acid is being dribbled into the beaker as it will want to flash to steam. Sulfuric acid is the method one uses to expel lead in solution. It converts it to lead sulphate, which will be filtered off when the solution is filtered after evaporation. Lower the heat and allow the solution to slowly evaporate. Do not evaporate too fast. Gold will be lost. After the solution gets concentrated, weigh a gold button and record its weight on your tracking sheet. Slowly introduce the gold button to the beaker (DON'T DROP IT IN) using tweezers. One should add some HCL at this point. The beaker should still be on the burner. If the button doesn't begin bubbling shortly after it is introduced, all the nitric acid has probably been used up or expelled by evaporation. That is unlikely. If no bubbling is noticed, evaporate the solution until it starts to thicken and leans towards a red color, then remove it from the burner and add about four (4) times its volume of water to it to cool it. Stir it as the water is added as the gold chloride will readily cool to a hard lump if it isn't diluted. You will need space in the beaker for wash water from washing

down the funnel and ice when you precipitate the gold, so don't use excessive water at his point.

You will more likely find that the button bubbles, as it is being dissolved, using up the free nitric acid. Keep it on the low heat and add more HCL when the solution thickens and darkens. You will notice that each time HCL is introduced the button starts the bubbling all over again. When HCL is added and it doesn't bubble, there is no longer any free nitric acid. Treat the solution from this point just as above, removing it when it thickens and leans towards red in color. A cautionary note. When the solution has gone too far in evaporation, gold will precipitate. As water is added, the solution will look something like brass paint, in that small particles of gold will be noticed, suspended in the solution. Should that happen to the lot, put it back on the burner and drop in a little nitric and HCL. Try to use a one (1) to four (4) ratio, as you are now building a small amount of aqua regia to re-dissolve the gold that has precipitated. Repeat the evaporation as above, using excessive HCL to insure total expulsion of nitric. One must evaporate the solution until it thickens somewhat, otherwise the free HCL makes it difficult to filter. The filter paper wants to break through when the acid level is too high. About all that can be done when that happens to you is to either dilute the solution with water or get it back on the burner and evaporate it all over again.

Filtering the Gold Solution

Fold a Whatman #2 filter paper and fit it to the polypropylene funnel. Be sure that the filter is fitted at the bottom. I have found that the top will pucker somewhat, but if the bottom doesn't have total contact with the funnel, it will probably split when the solution is introduced. Once the filter is fitted at the bottom, wash the filter down with the wash bottle to soften it. It will stay where you have put it once it is wet. Don't attempt to do anything with the paper once it is wet, as they have little wet strength.

Select a size beaker that will have about three ounces gold in solution per liter. Record its number on the tracking sheet then place it under the funnel and pour in the solution from the starting beaker. Once the beaker is empty, scratch its number from the tracking sheet so it won't be confused with the next batch that might use the same beaker.

When the gold solution has all filtered through the funnel, using the wash bottle, run around the mud that is deposited in the filter and wash it into the bottom of the filter, following up with a wash around the rim of the funnel until the color has been washed down well. The idea is to wash the gold trapped in the paper into the beaker. A little judgment goes a long way here. One tries to be honest with the customer without spending the better part of a life time washing. Experience will tell you when you have gone far enough.

Precipitating the Gold

When the wash water has gone through the funnel, fill the beaker with ice, staying away from the top at least 3/4 inch. Keep in mind that the water will expand as it warms during precipitation, and there is considerable bubbling of the solution if the sulphur dioxide one uses to recover gold is administered too fast. Using a vinyl hose, hook the sulphur dioxide bottle to the glass tube one uses for precipitation and slightly turn on the bottle, allowing the gas to bubble through the solution. You will notice a change in the solution almost immediately. It will cloud up with minute gold particles, and on occasion it will erupt into what looks like gold paint. As the process goes on, using the testing solution "A" (stannous chloride) check a drop of the solution to see if there is a reaction. One can expect to find platinum and palladium in their solutions as well as gold, so make sure of the reaction you find when testing. If there is a question about what is left in solution, with confusion between gold and palladium, place a drop of solution in the spot plate and sprinkle a couple grains of ferrous sulphate in the drop. If gold is still in solution, gold will be seen to grow around the crystal. It may look like nothing more than a grey cloud if not much is present. If there is no reaction, there is no gold in solution. If the "A" testing solution shows a reaction at this point, one can assume there is something from the platinum group in solution. Those values will be recovered in the stock pot. The platinum group won't precipitate from dilute solutions very well, so that is the economical way to concentrate and save them. Using the plastic policeman, stir the gold in the bottom of the beaker to get any solution trapped in the precipitated gold in contact with the sulphur dioxide. When all of the gold is down, turn off the gas and remove the glass tube and vinyl hose. Hold the end of the vinyl hose in the fume hood and blow through it to free it of any residual sulphur dioxide before storing it. Be very careful not to take a breath when doing this operation. I normally hold the hose some distance from my mouth when blowing, and I take the breath I use to blow with BEFORE I put the hose to my face. The first time you do it any other way, you will understand why I do it in that sequence. Clean the glass tube of all gold, returning it to the beaker. You will

scrape it with the plastic policeman outside, and a glass rod inside. Rinse the glass tube into the beaker, using the wash bottle filled with tap water.

Place the beaker out of the way and allow the precipitated gold to settle. There are times when the gold will settle down almost immediately, but you won't be surprised when it takes the better part of a full day. I normally precipitate at the end of the day, and wash the next day after it has settled.

Washing the Precipitated Gold

Using a short length of vinyl hose, siphon off the old solution into a catch container. If no gold is taken with the solution, it can be put into the stock pot. I have a habit of running everything through the stock pot. That way if there is anything of value it will be recovered, and any free acid is used up on the scrap steel, making a better solution to get rid of. After the solution has been removed, add enough HCL to cover the gold and place the beaker with a watch glass on it on the hot plate at a medium to high heat. Watch it carefully in this operation. NEVER LEAVE IT UN-ATTENDED. More often than not the beaker of gold will bump, and beakers that bump are known to walk or jump off the hot plate. If there is bumping action, one can move the beaker to a cooler part of the hot plate, or turn down the flame, but usually if a beaker is inclined to bump, there isn't a great deal you can do to change its mind. In some cases, there will be more of a popping of the solution and gold, with gold being blown out of the beaker. DON'T LEAVE IT UN-ATTENDED!

Bring the beaker to a boil then add about twice its volume of water to it, then continue to boil the gold for a half hour or so. Watch to see how it behaves. The idea here is to remove any residual contamination that was mechanically dragged down with the gold. The solution will darken as the boiling goes on. It is a good idea to check the solution to see if gold is being re-dissolved. That will happen to you when you haven't used up all of the nitric in the evaporation process. You will make the test with the testing solution "A". If there is a slight gold reaction with the testing solution, hook up the sulphur dioxide and precipitate the solution again. If there is considerable gold in solution, one may have to ice the solution to precipitate it. When the gold is down, put the beaker back on the burner and continue the washing process. Pour off the solution after about a half hour and replace it with more HCL and water and boil again. Do this until the solution doesn't change color when it is boiled. For a rinse, after the last acid is poured off, cover the gold with tap water and boil it for a few minutes. All of the solutions that have been poured off should go into the stock pot.

Drying the Gold Powder

Pour off all of the water then put the beaker on a low flame with a thick piece of asbestos pad under it and start the drying process. Occasionally shake the contents of the beaker so they don't dry glued to the beaker. You will notice in the drying process that the water goes off first, then there is some white fuming as the acid leaves. Once the water is gone, there is no risk of the gold popping, so the thick asbestos pad can be removed and the heat turned up to force the drying process. The gold should get lighter as it dries, and the color of the gold powder should be a light color when finished. The gold powder will bear some similarity to cinnamon powder, only lighter color. If the gold has a dark appearance and doesn't wash well, it should be high temperature roasted after it is dry. Place it in a stainless pan that is used only for this purpose and heat it on the hot plate. When it is quite hot, further heat it with the torch. If there is anything that will distill off, fumes will be seen to come from the gold. You can expect to see anything from white to black fumes, including red. The color of the gold will lighten up considerably. Heat it until no further fume comes off. DO NOT MELT THE GOLD WITH THE TORCH, but get it dull red hot. If nothing comes from the gold and it is still a dark color, it should be used as buttons for your added gold, as there is something in it that will continue to be a problem even if it is re-refined.

Weighing and Packaging the Gold

When the gold has cooled, weigh it and subtract the added gold from the yield. Calculate the percentage the customer gets. Refer to your chart of costs if you have any doubt about the amount to charge. Be certain to subtract for postage if it is to be mailed, and subtract any gold that has been advanced. Add any credit that may be due for platinum. If there is above six (6) ounces of gold net yield, one should multiply by eight (8) percent to calculate a silver return, if silver wasn't tracked. Remember that in the past nothing below 1/2 ounce troy has been returned in silver by Regal Refining. Make out your label and get it on a plastic envelope. Weigh out the fine gold you will give the customer and get it into the bag and heat seal it.

Do the same for silver, if there is more than a half ounce due the customer. You are now ready to deliver your customers metal. Remember they like to get their containers back.

The gold powder that was weighed should be put into storage for re-refining. Your customer should never be given this gold as it isn't of great quality.

Polishing Waste, Floor Sweeps and Ultrasonic Sludge

Because of the problems in filtering solutions that come from floor sweeps, polishing waste materials and ultrasonic sludge, the refining process you use will leave behind any silver that is contained in the waste. The silver that is left behind will be recovered when the residue is run through the ball mill and agitation tank in the future. Only if the bench man does a large amount of silver work will you run the material differently. Both cases are discussed here. Use the method that fits the situation.

Procedures

I am going to assume you are familiar enough with procedures at this point to know to record things such as the beaker number, added gold and any other information you need to track the individual batches. That will save entering very redundant information. If this doesn't make sense, go back and read the information under gold filings and pieces.

Incineration

Start the refining process with incinerating the material. Any low grade waste should be handled this way. Better stated, just about everything except filings and solid pieces of gold will be processed as floor sweeps or polishing waste.

Fill the stainless steel fry pan you will use to incinerate the material and get it on the hot plate. This material smokes a great deal as it is being burned, but if it gets up to heat it will generally support a flame, so try to ignite it as soon as possible to hold to a minimum the amount of smoke that comes off. As the pan heats, stirring it with a steel rod really helps. Try to turn the material in contact with the bottom of the pan to the top where the heat from the pan will encourage it to burn as it gets oxygen.

The material must be incinerated totally. All carbon should have been burned away. As the material is reduced it will shrink drastically. A full pan will end up about a sixth of a pan full when the job is done. When the pan is nearing the end, heat it to redness with your torch and stir the material to get it all up to near a red heat. Keep the torch moving around the pan. It burns through quite easily because of its thin walls. It is at this point that you will get rid of the carbon enclosed. When the pan is up to near a red heat, run oxygen from the torch over the contents. Anything not yet burned will glow orange. You want everything burned before you are finished.

Screening the Material

When the material has cooled, run it all through the two stacked sieves to get any large particles out so they won't be lost in the operation. What we do to the dirt won't extract values from large pieces, so we treat them separately. Run the magnet through the material the same as we did when screening filings, rubbing the magnetic particles well in the mortar then discarding them in the stock pot. Any aluminum found should be placed in the stock pot as well. Discard any lead or tin you find. Remember when speaking of tin we mean tin the element, not tin as in sheet steel. If it is magnetic, it goes in the stock pot. Return to the waste from the mortar anything the magnet doesn't pick up. (Normally fine dirt particles).

Dealing With the Solids >From the Goldsmith's Waste

Treat the material that doesn't go through the screens the same way you did when you screened filings. The obvious junk should be removed. Assume what you have left is gold, and inquart it. The exception here is that there is usually more base metal in this type of waste, so when inquarting you can usually get away with adding 100% silver to the weight instead of

110%. If you notice obvious large amounts of base metal, such as the small centers from abrasive disks, you can even simply melt the material without inquartation. Keeping that in mind, somewhere between no added silver and 110% added silver is where you will be. Experience will eventually tell you what to do.

The inquarted metal is melted and poured into water in the stainless drum. Part the resulting material with nitric acid to recover the silver and get the gold out so it can be added to the gold solution that will come from the dirt later. Refer to the section on gold filings and pieces if you are lost here.

Dealing With the Solids >From the Silversmith's Waste

After removing the obvious junk, melt the solid material and pour it into water as above. There is no need to inquart this material. Part the material as above to recover silver and gold.

Dealing With the Incinerated Dirt From the Goldsmith's Waste

After the dirt has been screened and the magnet run through it, using a 3000 ml beaker, place 1000 ml of the dirt in the beaker and wash the sides down with water. Pour in HCL slowly to make sure the material isn't going to froth and boil over on you. I suggest the level of acid be brought to about 2000 ml then add more water, perhaps to about 2500 ml. Stir slowly to get it all blended then put the beaker on a low flame and bring to a boil. Stir frequently so the material doesn't burn to the bottom of the beaker. When the contents start boiling, raise the heat and boil for about a half hour. Stir occasionally to make sure the mud doesn't cook to the beaker. When that happens you are most likely to lose the beaker. After the hard boil, remove the beaker and add water and blend well. Allow the contents to settle, then siphon off and add more water to wash the mud free of the dissolved contents. Normally there is nothing of value in the solution, but check with testing solution "A" to make sure. We are after the mud in this operation, not the solution. You will eventually discard the solution after it has settled for a good length of time to recover minute particles that are slow to settle out. Rinse the mud until the water comes nearly clear before you attempt to dissolve the gold and platinum the mud contains.

Dealing With the Incinerated Dirt From the Silversmith's Waste

The process differs here from the above operation in that we must recover the silver. Once the dirt is in the beaker, we use nitric acid, NOT HCL. DO NOT GET ANY HCL IN THIS OPERATION UNTIL AFTER THE SILVER HAS BEEN RECOVERED. After covering the dirt with water, add a small amount of nitric acid to the beaker and stir. The silver in the dirt will readily dissolve, causing the material to boil over. Go slow. Judgment here is the rule. You will apply enough acid to the dirt to remove a fair amount of material, then put the beaker on a low flame and bring slowly to a boil, stirring occasionally. When the material has boiled for a time, remove the beaker and take up the solution with water and let it stand to settle. We are after the solution in this operation, as it contains the dissolved silver. When the solution has settled well, siphon the solution from the beaker and get it on copper bars to recover the silver. Repeat the acid treatment until there is no activity. Wash the mud a couple times with water, once again placing the wash water on the copper bars to recover the contained silver. Like in all our operations, don't use any more nitric than is necessary to remove the silver, as it consumes the copper bars and makes a general mess when used excessively.

Incinerate Again

When the last wash water has been siphoned from the beaker, get the mud into a Shark Skin filter and dry the material as well as you can. The water from the filter should go on the copper bars. The mud and the filter paper now go back to the hot plate to be incinerated again. Our objective is to get rid of all the nitric acid contained in the mud so the HCL wash can take place before attempting to recover the contained gold. If the nitric acid isn't gotten rid of, gold will be dissolved when the HCL is introduced.

When the mud has been heated to dryness, run the torch over it until you don't see any further brown fumes coming from the pan. That is a good indicator that the nitric has been totally expelled.

Screen Again

When cool, screen the material to break it up, then get it back into a 3000 ml beaker again. A wash in HCL is the next operation, just as you would have done in the above entry for material from the goldsmith's bench. The objective is the same, for the same reason. Nitric acid removes the silver, but things that make for poor filtration are still in the mud and it is difficult to filter the gold solution that we generate. Don't bypass this operation. After the mud has boiled with HCL, rinse it as above until the rinse comes relatively clear. Two (2) or three (3) rinses will usually be enough.

Recovering Gold and Platinum From the Mud

Both of the above cases can now be treated the same way. We have gotten the mud to the point where we are now after the values, having taken out the base metals and things that make filtration difficult.

If your beaker contains 1000 ml of mud, a safe formula is to use three (3) ounces of nitric acid and twelve (12) ounces HCL to dissolve any gold contained in the mud. An excessive amount of HCL does no harm, and is a good idea. If there is a high amount of gold in the way of filings in the mud, there won't be enough acid, but experience has taught me that for almost all cases this is a good volume of acid to remove all gold and platinum in 1000 ml of mud.

After the acid has been introduced to the beaker, stir well and get the beaker on the hot plate on a low flame. Cover the beaker with a watch glass. It is unusual for this operation to boil over, as the amount of gold contained is usually low compared to the mud level. You will see fumes coming from the beaker and the mud will change color, usually from pink or purple to a yellow color. You are seeing the gold dissolve. Gold in solution is yellow. If there is a lot of jewelers rouge in the mud, it may not change color, but the solution will. Boil the contents for about a half hour, stirring occasionally. The half hour allows the acid to dissolve any filings that are sure to be in the mud. Remove the beaker from the hot plate and add a small amount of water and stir. Allow the solution to settle until clear of flocculence.

Gold Residue From the Parted Solids

Siphon or carefully pour the gold solution from the settled beaker into another beaker and begin the evaporation process. Add to this solution the gold that came from parting the solids. If you used enough nitric acid in the mud, the gold will readily dissolve. The exception here is that at first the large amount of water the solution contains will keep the acid from acting in a fast way on the gold that has been added. Allow the solution to concentrate by evaporation for some time before adding any more acid. If after some time the gold is still in the beaker, that is a good sign that not enough nitric acid was used in the mud to extract all the values. In other words, there is no free nitric and HCL present to dissolve the gold.

If no gold was added to the solution from parted solid material, when a gold button is added to the solution to consume the free nitric acid, there should be some reaction on it. If there is no reaction, you probably didn't extract all the values from the mud, and more acid should be added to the mud and it should be boiled again. That is most unlikely in this case, however. The amount of acid used is adequate except for the most unusual case. You can expect the solution will dissolve a fair amount of the added gold button, so make sure you add plenty. The fact that the button is dissolved is a sign that you didn't leave behind any of the values in the mud.

Finishing Up the Mud

Wash the mud one (1) time, using about 1 1/2 times the mud volume of water. Remember that you must evaporate anything that is added to this operation, so use good judgment. After settling, siphon off the wash solution, get the mud into a Shark Skin filter and let it drip dry, tapping the filter occasionally until there is no more solution dripping from the filter when it is tapped. The solution goes into the beaker being evaporated. From here the operation is no different than any other gold solution. If you are confused, refer to the section on gold filings and pieces.

When the mud has dripped dry, put it in pyrex dishes and place it below the burners in the hot plate to dry. You will store the waste in the storage bucket where we save material that will go through the ball mill and agitation tank to recover trace values.

The filter paper should be dried and incinerated along with other filter papers you accumulate. The resulting material is

stored for future reduction in the tilting furnace to recover values.

Refining Silver Waste

The material we will discuss is silver waste from the jewelers bench, along with silver contacts and dental amalgam. Again, procedure is assumed to be understood regards tracking the individual lots. If not, read the section on filings and pieces of gold.

Incinerating the Waste

As in all forms of waste material received, start the operation by incinerating. The incineration procedure for jewelers silver waste is the same as for gold waste. If you have any questions refer to the gold section for a clearer understanding.

Contacts need to be heated quite hot to burn off any oils that may be on them, but normally there isn't anything that will burn off like there is in bench waste. It is important to heat the contacts, as any traces of oil or grease bring problems later when the silver is being dissolved. If contacts are received with the copper buss bars attached, the action of heating them with the torch to remove the contact from the buss bar is heat enough to clean them, as they are heated to a dull red heat to melt the solder bonding them to the bars. If the buss bars are copper, they are a great source of copper for recovering silver. They should be melted and cast into bars. Silver plating on them is also recovered by using them this way.

Dental amalgam will be handled differently. DO NOT INCLUDE IT IN THIS PROCESS. DO NOT INCINERATE DENTAL AMALGAM AT ANY TIME!

Screening and Sorting

Any clean silver received that is clearly marked for content should be removed and weighed to calculate content and a settlement made with the customer. Sterling silver is 92.5% pure silver, U.S. coin silver 90% silver, except for Kennedy half dollars, 1965-1970, which are 40% silver. Silver Canadian coins are 80% silver. Any alloy other than 92.5% silver is not referred to as sterling. In the Scandinavian countries, silver is marked with numbers like 830 (83%) or something similar.

The reason you should remove known clean silver is that there is always a shortage of silver for inquarting gold, and it isn't the smartest thing one can do to refine silver to pure to return it to the system to be used for inquartation when the alloyed material received does the job nicely, while taking the silver through the system at the same time.

After incineration, screen the silver waste exactly the same way you treat gold waste. Everything that won't go through the screens will be melted, but in this case there is no inquartation. The reason we melt the waste is that it is unusual for a bench worker that works in silver to not get at least a little gold mixed with the waste. By melting everything, one can get it all processed in one fell swoop, leaving the gold that might be present ready to be further processed. You can't always pick out the gold, as when white gold is present, it is easy to confuse it with silver. The melting process also cleans the material and makes processing it a lot easier, as any dirt that may be included with the metal is removed.

Processing the Screened Material

The material that has gone through the screens should be placed in a beaker that allows plenty of room for boiling over, as the silver particles react readily with the nitric acid you will use. Cover the dirt with water and slowly add nitric acid to the beaker. Stir as the acid goes in. If you pour in the acid totally then stir, it is possible that the silver put into suspension by stirring will immediately react with the acid and the beaker will boil over, then settle rapidly. STIR SLOWLY AS THE ACID IS ADDED! There isn't a formula for how much acid to add, so add some to the lot and let it work until it is exhausted then boil it slowly on the hot plate. When there isn't any activity, take up the spent acid solution with water then either allow it to settle quite well or pour it off into another container and let it settle. It's a good idea to let it settle over night. At first the solution will be very muddy looking, but as it settles it will turn to a slightly opaque blue color. The solution should then be siphoned off and placed on the copper bars to recover the contained silver. Repeat the nitric acid process until all the dirt that

is present is either dissolved or the nitric acid has no further effect on it. Don't use any more acid than you need, as it will consume the copper bars, making a lot of gas and waste your copper.

Combine all the mud from the settling container(s) with the mud in the beaker and add a little nitric and water and bring to a boil to insure that silver particles weren't poured off early in the operation. After that has been done and the material has been washed a couple times with water, get the mud into a funnel, using a Shark Skin filter paper, and separate the balance of solution from the mud. All of the wash water and spent acid solutions from this operation should end up on the copper bars, as the solutions contain silver. When the mud is quite dry, incinerate it, playing the torch on the mud towards the end to insure that all the nitric acid has been expelled. After the water has been expelled, you will notice brown fumes coming from the mud as the acid comes off. The fumes will be absent when the job is done. Stir the material with a steel rod, (the piece of rebar used in incineration) making sure that it all gets hot. It is important that all the nitric be removed in this operation, otherwise gold will be dissolved in the HCL wash which we will talk about shortly.

Melting the Solids

The bits of metal that didn't go through the screens and weren't removed earlier are melted. Remember to remove any aluminum, stainless steel or anything magnetic. If there is a lot of metal, use the crucible furnace to melt the remaining metal. Small amounts can be melted with the torch in a melting dish. The material should be brought molten then a little soda ash added, then some borax. The metal should be poured off into a cone mold. After it is cool, chip the slag and remelt the metal and pour it into water in the stainless container to get the material into small pieces for dissolving in nitric acid.

Processing the Melted Metal

Dissolve the metal with nitric acid and water, just as you do inquarted gold. The difference here is that small amounts of gold will be contained in the silver. Notice that the pieces you are dissolving turn black soon after acid is poured on them. You will notice very fine black particles in SUSPENSION in the solution. (NOT in solution. There is a difference). If you don't experience the black appearance and the fine black particles in suspension, you probably don't have any gold in the silver, or there is very little gold present. Allow the solution to settle well before pouring it on the copper bars to extract silver. When the job is done, filter all the mud using either a Shark Skin or the less expensive filter paper from VWR. You don't need to waste the quite expensive Whatman #2 and #5 papers for this operation. You will have siphoned off the bulk of the solution. Filter only the small amount remaining. It won't run through the filter well. The fine black gold particles like to go through the paper in this operation at first, so you may have to re-filter the first solution through the paper. As the paper loads with mud, it will stop the fine particles from getting through. The filter paper should be incinerated when this operation is done and the residue added to the dirt residue after silver has been removed.

Incinerating the Once Processed Mud

After incinerating the mud, along with the black mud that has come from the solids that were melted and parted, screen the caked material again to get the cake back to fine powder. When that operation is done, get the fine powder back into a beaker and wash it with HCL (hydrochloric acid), again on the hot plate on a low flame. This operation is no different than the one you use to process silver barren floor sweeps and polishing waste after incineration. The idea here is to remove anything from the mud that will give you problems in filtering the gold solution that comes from adding the aqua regia after this operation.

Slowly heat the beaker that contains water and HCL until it comes to a boil. Once it is boiling, raise the heat. Allow it to boil for a time, perhaps a half hour. Stir the material all the time it is getting to a boil and occasionally while it is boiling. When stirring, don't grind hard on the bottom of the beaker with the stirring rod. The dirt is quite abrasive and wears away the beaker.

Should you cook the material hard to the bottom of the beaker because you didn't stir it, there is a good possibility that you will end up with a broken beaker. STIR THE BEAKER OFTEN! If you find a hard deposit on the bottom, the best thing to do is allow the beaker to cool naturally. Once cool, pour off everything that will pour off after stirring, then rinse the beaker well with water. Pour in enough HCL to cover the bottom and add water. Put it back on a low flame and let the new acid and

water slowly dissolve the hard cake. There are times when even this will result in a broken beaker. Don't try to dissolve the hard cake by boiling the mud, as all that happens is a thicker cake, with breakage for sure.

Assuming that you haven't formed the hard cake on the bottom, after the material has boiled long enough, remove the beaker and add water to it, filling as full as space will allow, keeping in mind that you will want to stir the contents to blend everything. After things have settled, siphon off the wash solution and rinse the mud with water again. Repeat this operation until the rinse water is quite clean. Three (3) rinses will generally be enough, and at times two are sufficient. If the solution is clear of color, it is washed well. The solution that is siphoned off should be allowed to settle for quite some time before discarding so the fine particles that hadn't settled won't be thrown out. It doesn't hurt to check the solution with testing solution "A" to make sure it doesn't contain any dissolved precious metals. On occasion, gold will go into solution in this operation. Should you find the solution contains values, pour the solutions in the stock po

Gold and Platinum

After the last wash solution has been siphoned off, add enough aqua regia to the mud to extract gold and platinum group metal that may be included. Experience here will really help. Look at the mud and try to determine if it is loaded with gold filings. The mud should have a light purple to pink color if it contains very fine particles of gold, and you may notice gold filings when you move the mud about. Use the ratio of one (1) nitric and four (4) HCL to make your aqua regia, and use that amount for each ounce of gold you expect to recover. Extra HCL does no harm. After boiling and allowing to settle, the procedure for finishing the solution is not different from the gold solutions you are familiar with. If there are any questions, refer to the gold section. Keep in mind that you may NOT have removed all the values in the aqua regia operation. Siphon off the solution containing gold and take up the mud with about 1 1/2 times its volume with water and stir. After the wash solution settles, siphon it off and add it to the first solution that is on the hot plate evaporating. Get the mud into a Shark Skin filter and filter it, adding the solution to the evaporating dish.

At the point you add the gold button to the evaporating solution to use up the free nitric acid, if you don't have any action on the button, you probably will have to add more aqua regia to the mud. You normally will have used a little more acid than there is metal to dissolve, and if there is no excess acid in the solution, you probably left gold and platinum behind in the mud.

The gold solution at this point is no different from any other gold solution, and it should be processed to the end in the same way. Refer to the gold section if you are confused.

When you are sure you have the values extracted from the mud, the force dried mud will go into the storage container where you save floor sweeps and polishing wastes after they have been processed. They eventually will be run through the ball mill and agitation tank with cyanide to remove trace values of silver and gold.

Processing Contacts

After the contacts are off the buss bars and roasted to free them of any oil or grease, place them carefully (don't drop them as the beaker will be broken) in a beaker and add nitric acid and water and boil them on a low heat until the acid is spent. You probably won't have any trouble with contacts boiling over if the beaker is large enough. They don't have a lot of surface area so they dissolve slowly. Take up the spent acid solution with water then after the flocculence has settled pour the solution on copper bars to recover the silver. Repeat that action until such time that the contacts are either gone, or the remaining skeleton is brittle and breaks easily under the thumb when bent. The skeleton will be tungsten, and not all contacts contain it. Tungsten is very heavy, with a specific gravity of approximately 17. The silver is the binding agent in tungsten contacts. If the silver is not totally extracted, you will see a silver line in the center of a broken contact. When the silver is totally extracted by the nitric acid, the contact when broken will be a dull dark grey through and through. Tungsten contacts generally have a waffle pattern on the back side which helps you identify them. It is a good idea to dry and store the tungsten after the silver is removed. It has a salvage value.

The Silver Mud From the Copper Bars

After the silver has been extracted from solution on the copper bars, the silver should be collected from all containers and washed with water. Using the large buchner funnel, put in a #2 Whatman filter paper, wet it down and start the aspirator. Slowly pour in the silver mud, tamping it down as the funnel gets full. The idea here is to get all the silver in the funnel and wash it until the wash water comes clear. At the end, tamp it down quite well and wash down the sides and allow the aspirator to run until there is very little water dripping from the funnel. At that point remove the funnel and get the silver into a large stainless pan and force dry on the hot plate. You will notice a small amount of nitric acid fuming off (brown smoke) when the silver gets hot. Heat it until the fumes quit.

The silver will be melted in the crucible furnace, using ONLY BORAX which is added AFTER the metal is molten. Adding the borax to the heat before it is molten causes some of the silver powder to go into the flux, in effect causing you to lose it. We don't add any soda ash because it will reduce copper oxide and put the copper back into the silver. Our objective is to remove the copper, and borax does that. When the flux that has been added is up to heat, slowly pour the flux into a recently coated cone mold, then the silver. After cooling, chip the flux. When you have about one hundred fifty (150) or more ounces of the cones of silver, they can be melted and poured into an anode. I suggest you don't make the anodes heavier than two hundred (200) troy ounces. They must be handled in the silver cell, and the heavier they are, the more difficult the handling. If a small amount of flux is poured with silver when an anode is poured, chip it off. The anode is now ready to be parted in the silver cell.

Dental Amalgam

Working with dental amalgam leaves a great deal to be desired, but it goes with the territory. The reason we NEVER incinerate the amalgam is mercury is distilled off. To remove the mercury, a retort is employed, so the mercury can be safely captured and stored for future sale.

Filling the Retort

Remove the six (6) clamps around the flange of the retort and make sure there is a bottom cover of asbestos in the retort. Two thin halves of asbestos are used. They prevent the charge from fusing to the bottom of the retort when it is heated to redness.

Spoon in the amalgam, watching for crowns and parts of crowns or gold fillings. Any gold that is seen should be removed and refined in the usual manner for dental gold. If any is missed, you will find it in the beaker after the silver has been dissolved after it has been retorted.

An asbestos gasket should be cut and placed between the flanges before the retort is closed. It should be one piece. DO NOT USE A GASKET WITH ANY TEARS OR BREAKS IN IT. The clamps should be tightened a couple times, making sure a full seal is made. You don't want any mercury vapors leaking while the retort is running. Don't tighten the screws excessively, as they will twist off. Simply make sure they are all quite snug.

REMEMBER: MERCURY KILLS!

Running the Retort

The ideal place to run the retort is under a hood, or an exhaust system of some kind as the smell that comes from retorting will remind you a lot of cooking your neighbors dog over an open fire.

Before placing the retort in the small incineration furnace, on top of the four (4) stainless steel bars that support it, a sock made of cloth should be tied to the discharge tube at the bottom of the retort. The sock will be the connecting link with the cold water and soap solution that the mercury will collect in. It's purpose is to prevent water getting siphoned into the retort. The cloth will be barely in touch with the water and will be wet when it is in use. The collection container can be a 1000 ml beaker. Add a generous amount of liquid soap to the water to help dissolve the dirty stinking oils that are discharged from the

amalgam.

A five (5) gallon bucket of cold water serves as the cooling medium for the retort and it will cool the retort for several hours of running. The circulation pump should be placed in the bucket with the pump discharge vinyl hose connected to the BOTTOM connection of the cooling chamber. Don't put the water in the top one, as it may not fill the cooling chamber totally. By introducing the water to the bottom, it must fill the chamber to the top in order to discharge, insuring the cooling chamber does its job. The discharge hose is connected to the top fitting and the hose end placed in the water bucket. Make sure it doesn't end up out of the bucket. Plug in the pump and watch for bubbles to come from the discharge hose, then a water flow as the system fills. If all is proper, turn on the gas, plug in the small blower and light the furnace, setting the flame where it is burning totally in the furnace.

You want to get the retort to a red heat eventually. As the retort heats, smoke from the oils and other junk in the amalgam will be seen to come from the collecting beaker which you have placed under the sock. Eventually you will see beads of mercury drop from the tube and collect in the beaker. Run the furnace until the retort has turned quite red. It helps to lightly rap the discharge tube of the retort near the bend at the top. That will dislodge any mercury that has condensed at that location and either put it back in the retort or cause it to run into the collection beaker.

When no more mercury is being discharged from the retort and it is up to a red heat, turn off the gas and unplug the small blower on the furnace and allow the retort to cool. You should also lower the beaker that is collecting the mercury so that only the tip of the sock is in contact with the soapy water in the collection beaker.

After the retort has cooled, open the retort and remove the charge, which now will be a fused piece in the bottom along with many small bits that didn't get combined with the melt. You will see small bits of mercury that have dropped off the lid of the retort. We will deal with the traces of mercury before we process the material with acid. Repeat the operations until all the amalgam has been retorted. To clean the mercury, stir the soapy water and mercury then allow it to settle. I have found that acetone will dissolve the oils nicely. Mercury can also be washed with HCL. Do not wash with nitric acid, as it dissolves mercury. The mercury that comes from the retort is of poor quality and should be well washed and retorted again in a clean retort before it is used for any purpose. The retort can be cleaned with acetone and the flex cable that comes with the retort. When retorting dirty amalgam, such as the material that comes from the dentists sink traps, clean the retort often as the discharge tube gets plugged with oil and gunk readily.

Roasting the Retort Cake

When all the amalgam has been retorted, place the cakes and all the dirt that comes from the retort in a single layer in a stainless fry pan and put it on the burner in the hood. You want a good air flow to do this operation, so if the filter in the hood is getting plugged, replace it with a new one. Heat the pan with the hot plate, then with the torch. You will see the traces of mercury that remain go off in a white cloud. Don't breath any of the smoke and fumes that come from this operation. They can kill you! As the cake comes up to heat, it will begin to melt. It is an alloy of tin and silver, with a trace of copper. Stir the cake and get it totally melted. You will find it doesn't get real fluid, but sort of crumbles along with some molten metal. Stir it and continue to heat it. You are trying to oxidize the tin so it isn't a problem when you dissolve the silver with nitric acid. When the appearance of the metal changes to a dull white/grey, turn off the torch and burner and continue to stir to insure that the entire mass is broken up into small bits. When they are cool, you can start the extraction of silver.

Extracting Silver From Retorted Metal

With the material in a beaker, apply nitric acid and water to dissolve the silver. This mix doesn't give you much trouble regards boiling over. What does happen here is the tin is gradually converted to a white powder which is in suspension in the solution. Boil the beaker until the nitric acid is spent then take up the solution with water and pour it off to settle. Repeat this operation until there are no small pieces of metal to dissolve. You will find any gold in the bottom that you may have missed, and all of the tin will have been converted to white powder. Collect all the powder and wash it with water, removing the silver. When it is washed free of silver, or nearly so, filter the powder using a Shark Skin filter paper, then dry it in the pyrex dishes you use to dry floor sweeps and polishing wastes. The cake when dry should be put in the storage drum along with the floor sweeps and polishing wastes that eventually will be re-processed in the ball mill and agitation tank.

The solution from this operation should be allowed to settle until there is no flocculence suspended in it, then it should be siphoned off and placed on copper bars to recoverer the silver that is in solution. The solution will be a pretty pale blue. After the silver has been recovered on copper, wash the mud and filter and dry it. It is now ready to melt. If you need silver for inquartation, the silver from this operation is quite good to use, as it shouldn't contain any platinum. After melting the silver cement and cleaning the flux from the silver button, it can be remelted and poured in water to give you the fine silver shot we use for inquartation.

To settle with your customer, after melting the silver and pouring the silver cone(s), assume it to be 98% pure.

Running the Silver Cell

The objective in running the silver cell is to bring the relatively high grade silver we have recovered in earlier operations to a pure state, extracting the contained precious metal values in the process. As you know by now, silver carries the platinum group with it if it was present in the earlier operation when silver was recovered. Further, while we are careful not to lose gold in the parting process, one can expect to recover at least an ounce of gold when running a thousand ounces of silver. The way we get it back is to part the silver electrolytically. The silver will grow out as crystals in the silver cell, and the residue that remains in the basket filter will contain the values we are looking for.

You must be aware of a few things when running the silver cell.

NEVER USE TAP WATER IN THE SILVER CELL. ONLY DISTILLED OR DE-IONIZED WATER CAN BE USED.

ALWAYS KEEP A PAIR OF CLEAN GLOVES AT THE CELL, AND USE THEM WHEN EVER YOU DO ANYTHING IN THE CELL. DON'T USE YOUR NORMAL WORK GLOVES. DON'T CONTAMINATE THE CELL WITH DIRT.

NO CHLORINE (SALT - HCL - ETC.) OF ANY KIND CAN BE INTRODUCED TO THE SILVER CELL. IT WILL PRECIPITATE YOUR ELECTROLYTE AS SILVER CHLORIDE.

KEEP THE PLASTIC COVERS IN PLACE WHEN THE CELL IS RUNNING. WHEN REMOVING THEM TO KNOCK DOWN THE SILVER, ALWAYS BLOW THEM OFF FIRST TO REMOVE ANY DUST THAT COULD DROP IN THE CELL.

Setting Up the Cell

Begin setting up by cleaning the silver cell completely. It must be wiped down or even scoured with a plastic sponge and cleanser if necessary. The interior of the silver cell is the area that silver will be deposited on. The silver will be only as clean as the interior of the cell. If you use cleanser, you must rinse the cell very well as it normally contains chlorine bleach, and that is death to silver nitrate, which your electrolyte is made up of. The silver cell should be totally dry or have been rinsed well in distilled water before setting it up. I normally rinse it in hot water then towel dry it. The heat from the hot water will dry it totally if it is wiped right after it is rinsed. All parts of the cell should be cleaned as above.

The Filter Bag

Filters for the silver cell are made using the aluminum pattern that came with the silver cell. Using a ball point pen, trace the outline from the pattern on the material (which is described below) then cut it out and sew the corners. Sew a double seam so there is sure not to be any leaking of the slimes that collect in the filter bag. The fuzzy side of the material should end up on the inside of the bag, along with the corner seams.

Filter Material

Purchase filter material from:

National Filter Media Corp.

691 North 400 West

Salt Lake City, UT 84103

You will purchase their material NFM style # 112 113 980, 58" wide, cotton. A yard or two will last you quite some time and it isn't expensive. Make sure that the filter bags are clean when you are finished making them. Wash them or the material in your washing machine if you must.

Assembling the Silver Cell

Having gotten the silver cell clean, the next step is to install a filter in the basket. The filter is where you will accumulate the residue mentioned above. Notice that the filter basket is not quite square. Place the long side of the sewn filter bag along the long side of the basket, fuzzy side in, and roll the edges over the top. Notice that there are two different size clips that hold the bag in place. Two sides of the basket are made of thicker material than the other two. Place the clips, three to the side, over the folded over the top bag, one in each corner on each side, one in the middle, around all four sides of the basket. The bag should fit loosely in the basket. You don't want it pulled tight anywhere. Place the basket in the silver cell in the center, then put in an anode. I normally put the top face of the anode down, leaving the bottom for the candlestick to make contact with. It tends to be somewhat cleaner than the top, making for a better electrical connection. Place the two covers on the cell to keep out dust and dirt.

Making Electrolyte

Using a well washed and dried 4000 ml beaker, place two pounds avoirdupois (29.2 ounces troy) of silver crystals in the beaker and cover it with one liter of HNO3. That is exactly the right amount to make one batch of electrolyte. Add to the beaker about one liter of water. REMEMBER: the water must be distilled. As you are starting out with cold solutions, the silver won't boil over on you. Place it on a burner at a medium heat and cover it with a well washed watch glass and dissolve the silver. It will take about a half hour to totally dissolve. The solution at first will have a strange green color to it. As the silver dissolves and the nitric acid is used up, the solution should change color, leaving you with a very pale yellow color when the silver is gone. If there is any other color, check the electrolyte with testing solution "A" after a drop of HCL has been placed in the spot plate with the test drop of solution. If you get any color reaction, you have dissolved silver of not great quality. It is normally contaminated with palladium or copper when you have run the electrolyte too long. If copper is in your silver, the solution in the beaker will have a green to blue cast to it. The electrolyte is alright to use, but the silver that has come from the cell shouldn't be dispensed to a customer. I have simply put it in the filter bag as crystals and parted it again with new electrolyte. It takes time, but the batch will run almost free regards electrolyte usage as it has very little contamination. When the crystal is gone another anode can be placed in the bag and processed.

Putting the Electrolyte in the Silver Cell

When the silver has dissolved, pour about a liter of water (distilled) around the edge of the beaker to wash it down some and cool it so you can handle it comfortably. Pour the contents into the silver cell, then wash the beaker out with more distilled water. You will use this beaker to clean out the silver cell eventually, so place it near by and cover it with the watch glass. Going back to the silver cell, you will now add enough water (distilled) to the cell to bring the water level up to just cover the three plastic rods that come out of the side of the filter basket. The idea here is to have the electrolyte just touch the bottom of the anode. You want to eat it away from the bottom, not the sides. Stir the electrolyte with the stainless steel handled plastic knock down tool, then test the ph with the test paper you have been supplied with. You want the ph to be between 1 and 1 1/2. If you find it above 1 1/2, add about twenty (20) drops of HNO3 from your dropping bottle. Stir again and test again. Repeat this function until the ph is where it should be.

Connecting Electrodes and Setting the Voltage

Put the silver candlestick in the clamp on the black lead of the power supply and place it on the anode. You will have to support the lead from overhead by some means. Don't allow it to lay over the side of the silver cell. Connect the white lead to the ground lug of the silver cell. It is located on the back side of the silver cell on the right hand side. Turn on the rectifier and set the voltage at four (4) volts when the candlestick is removed from the anode (open circuit voltage). That is only a point at which you will start. What you want is for the silver cell to run at ten (10) to twelve (12) amps when it is up to operating temperature and the bag is wet totally. Operating temperature is warm to the touch. It will get there by running. The voltage will vary slightly from batch to batch. The amperage is what you will monitor, and you will set the voltage where ever it must be to have the amperage you desire.

Starting the Silver Cell

Your work is now done regards starting to run the cell. You will just monitor the cell, knocking down the silver crystals when they need to be knocked down, and clean the slimes off the anode each day and remove them from the basket. If you don't clean out the slimes, you will end up with a barrier that will eventually deplete the electrolyte, causing your cell to produce poor quality silver. If your anodes are quite pure you typically can run a full anode and get started on a second before the electrolyte needs to be replaced.

When the silver that grows from the cell starts to turn to hair and the electrolyte is getting quite dark, it is time to replace it. If you have a doubt about the silver that has been produced, some of it can be dissolved to make the next batch of electrolyte. The silver that is dissolved should make an electrolyte that is just slightly off clear in color, leaning to a pale yellow.

Knocking Down the Crystals

Remove the plastic covers, blowing each off before you pick them up. They will have a good amount of water that has collected on the bottom side. Tip them with a corner emptying into the silver cell and allow the water to run in, one at a time. Place them where they won't pick up dirt with the inside surfaces facing each other to keep them clean.

Remove the candlestick and place it away from the silver cell. Don't make contact with the silver cell with it. Remember the silver cell is the other half of the electrical circuit. Pick up the basket and place it at the right end of the silver cell. The silver cell is slightly tapered and the basket will sit nicely inside without dropping in deep.

Using the stainless steel scraper with the plastic end, scrape the sides and bottom of the silver cell, dragging the silver crystals to the left hand ramp and storing them, still in the electrolyte.

Place the plastic covers next to the basket, covering the cell. The next operation tends to splash, and you don't want any of the slimes to end up in the cell.

Scraping Slimes From the Anode

Stand the anode on its end against the back side of the basket. Using a porcelain spatula, scrape down the bottom face of the anode. You will find a layer of slimes that has been left by the parted silver. If the gold, platinum and palladium is in great concentration, the slimes will be quite hard. Be sure to scrape the anode to clean silver.

The slimes you have removed should end up in the bag inside the basket. The next step is to use an acid dipper and remove all the slimes that you can gather, placing them in a storage container for later processing. Normally you will have spent enough time doing other things that the electrolyte has dripped through the filter. Try not to remove any more of the electrolyte than necessary. It is acceptable practice to pour electrolyte that has been removed with the slimes back to the basket where they will filter through the bag and get back to the cell.

When you have the slimes removed, replace the anode in the bottom of the basket and return the basket to its operating

position in the cell. Check the level of the electrolyte. As the cell runs for days on end, you lose water to evaporation. Just like when you set up the cell, you want the electrolyte level to be just above the three plastic knobs on the end of the basket. If you have washed any silver prior to this, the wash water from the crystals is the make up water used. If not, use distilled water. If only a little is added, don't worry about stirring the cell. The natural handling of the cell will soon enough mix the water with the electrolyte.

Pulling Silver From the Cell

When the cell is either quite full, or you have run about 150 ounces of metal, it is time to remove the silver and wash then dry it. The procedure is the same as when you are going to knock down the crystals. With the basket on the right end of the cell, use the stainless steel handled scraper to get all the silver free in the bottom of the cell. There are a couple plastic scrapers (actually kitty litter spatulas) that work out nicely in removing the silver from the cell. Use them together to clamp the silver and place it in the 4000 ml beaker that the electrolyte was made in. Hold the mouth of the beaker over the cell so you don't lose electrolyte in making the transfer. Remember that the electrolyte is made of silver and you don't want to lose the values.

When the cell has been emptied, if the electrolyte is still good for further use, replace the basket, check the level of the electrolyte and get the cell running again. If it is contaminated and needs to be replaced, after getting the silver you have pulled washed and on to dry, you will make new electrolyte and start over.

Washing and Drying the Silver Crystals

You will use a large buchner funnel to wash the silver. There is a filter flask, buchner funnel and large evaporating dish that you will use only for silver crystal. Keep them clean always and it helps in making the work go faster.

Hook the aspirator hose to the filter flask, place a Whatman #2 paper in the funnel and wet it down with distilled water, using the large wash bottle that you keep filled for such use. When you have the water running and a vacuum established in the flask, use a clean large glass stirring rod and get all the crystal into the buchner funnel. Wash down the beaker with the wash bottle filled with distilled water. Everything should end up in the buchner funnel. Tap the buchner side to side with your hands to level the silver nicely. You should have been wearing the clean gloves you use for the silver cell work through all of this. When the silver has settled down nicely, rinse the crystals with a small amount of the dirtiest wash water that you have saved from previous washes. If you are starting out with your first batch, use a small amount of fresh distilled water. Don't use a lot in this operation as you will not save the first wash. It is usually quite contaminated and should be placed on copper bars to recover the silver and palladium that is usually present.

Allow the aspirator to run until there isn't much dripping from the funnel. You want to get as much of the green colored solution away from the silver crystals as possible. When you are satisfied that you have gotten the bulk of the solution in the flask, IN THE FOLLOWING ORDER remove the hose from the filter flask, then turn off the water. If you have gotten any of the water from the aspirator in the hose and turn off the faucet, the vacuum from the flask will pull tap water into the flask. Tap water has chlorine in it and you will contaminate the flask. While you are going to discard this solution, not return it to the cell, the next batch of solution you will save, and the chlorine will have already done its damage to the flask, precipitating some silver chloride from the next wash.

Take the filter and flask to a bucket that you will pour the solution into. Remove the buchner funnel from the flask and hold it over the bucket to catch any drips that come from it while you pour off the flask. Take the flask back to the sink area and put the funnel back in. Using more distilled water, cover the silver crystals but don't start the aspirator right away. Allow the water to sit on the crystals, diluting the silver that is on them. When the level of water drops a little below the silver, start the aspirator again. You will repeat this operation three times. By the end of the third wash, you will have crystals that are almost free of silver nitrate. They will dry nicely without any problems.

The Wash Water

As you wash the silver crystals, it is probably apparent to you that the solution you end up with will have more or less contamination in it. You have paid a price for distilled water and there is no reason to not use it until it isn't any good for the

use intended. I suggest that the first wash after the one that is discarded be stored in a bottle and used for make up solution and the first rinse of the next batch of crystals, should you still have any of it. The second rinse is made up of the solution that has come from previous washes, less contaminated. Each wash, in other words, should be stored in order of its level of cleanliness. In that way you promote the water to dirtier and dirtier use. The final wash is always with unused distilled water. All of the washes will be allowed to stand on the crystals until they have dropped below the silver line a distance. When new electrolyte is made, all of the wash water should be used in making up the electrolyte after the silver has been introduced to the cell. In that way you always keep the freshest water possible.

Drying the Crystals

After you have run the aspirator until there is no dripping, remove the hose, turn off the aspirator (faucet) and remove the buchner funnel from the flask. I will assume you have already cleaned the large porcelain evaporating dish. Be careful with this operation as you can easily break the evaporating dish. Place the evaporating dish on the funnel, upside down. Carefully turn both the funnel and the evaporating dish over. You want to empty the crystals into the evaporating dish. Not all of the silver will want to drop off the paper in the funnel. I usually tap the sides of the funnel until most of it has dropped then I place the buchner where it will keep clean and allow it to dry a short time. You will find that the rest of the silver will drop off as it dries. Get it into the evaporating dish as soon as possible to force dry it.

Set up the three legged stand with the high temperature burner under it. Place the coarse screen on the stand and make sure you have at least one layer of asbestos on top of the screen. Two layers make for a more gentle distribution of the heat. The porcelain dish will take a lot of heat, but it doesn't tolerate heat change well. You must heat the dish slowly or it will crack. Turn on the valve and light the burner. You will set the flame very low. While your silver is drying, it makes good sense to not make dust in the room. You don't get ahead much by dirtying the silver after it has been purified. The silver will normally dry in about an hour. Busy yourself with other things and allow it to dry without contaminating it. When the silver gets warm, you can kick up the heat some, but never run a high heat from the burner to avoid cracking the dish.

When the silver is dry, remove the heat and allow the silver to cool. If you remove the evaporating dish from the stand, place it on something that won't cool the bottom rapidly, as, once again, the dish will shatter from abrupt temperature changes.

Storing the Silver Crystals

When the crystals are cool, it is a good idea to have a five (5) gallon bucket that is very clean, along with a fitted lid to keep out dirt to store the silver in. Store the silver crystals in. You may not have much silver now, but that will change rapidly as you continue to refine.

Fee Structure for Silver

Regal Refining in the past has refined silver for 20% in quantities under 100 troy ounces pure. Over 100 ounces troy the fee is 15%. I don't feel that you should ever run silver for less than that, as you will see that the labor in refining silver is rather excessive and a profit is barely made at 15%. You must have the silver and remain competitive, so the 15% pays the bill and give you the silver you need to process gold.

Dispensing Silver

The customers you now have are used to receiving silver crystals just as they are removed and washed straight from the silver cell. Certainly one can melt the crystals and pour silver shot, but that is one more operation which takes time and costs money. I recommend you continue to dispense the crystals unless you have problems with a customer. Even then, it might be better to get rid of the customer. You will have to make a judgment at the time of the problem.

Save plastic containers that have large screw lids. They make nice containers for dispensing the silver crystals. NEVER place the crystals in a metal container. The plating on the inside of metal containers migrates to the silver, in effect lowering the quality of the silver.

Dealing With Spent Electrolyte

Returning to the silver cell, fill a hose with water to siphon the electrolyte from the cell. You have about two (2) gallons of solution to deal with, so have at least two buckets readily available. As the first bucket fills, you can almost stop the flow of the hose by touching the hose flat against the bottom of the cell. That allows you to direct the hose to the second bucket. Have the two buckets very close to one another. By the time you have most of the electrolyte out of the cell, it can be picked up (you will have placed the basket on the holding container that houses the slimes) and pour off the solution that didn't siphon off. Wash down the silver cell with the large wash bottle until the bulk of the green solution is gone. Pour the wash water into the spent electrolyte container. Remember to use distilled water.

If you have done proper work, the spent electrolyte should contain the roughly thirty (30) troy ounces of silver that you started with, along with some palladium. It is palladium that makes the electrolyte green instead of blue. If you are curious about this, test the solution with test solution "A" after putting a drop of HCL along with the sample drop to expel the silver. You will get anywhere from a light brown to a dark brown reaction, and if there is way too much palladium it may even be blue to green in color. Palladium gives you a lot of different reactions, and nothing but time will familiarize you with them all. You can also test with DMG. You will get the familiar canary yellow precipitate with DMG.

The spent electrolyte should be placed on copper bars to recover values. Naturally, the silver and palladium that comes from the copper bars gets washed, melted and again cast into an anode.

Pitfalls

Running the silver cell is where you pay a price for poor work earlier. It is important that the silver going into the cell be as pure as possible. Try to keep copper out of the cell. Wash your silver MUD (not the crystals) very well before drying and melting it. Don't melt any copper with the silver mud. Pick out even tiny pieces of copper if you see them. Don't use small pieces that are easily lost to recover silver. Don't ever use copper wire to recover silver. If you have clean copper wire or small pieces, melt them and pour a bar that is easily recovered from the copper solution and the silver mud. What I am saying is that you should keep everything out of the silver that you can in the early operations so that the silver you melt to pour the anodes is almost pure. It makes a big difference on how long you will use your electrolyte. If you do good work early, you should be able to run at least 200 ounces troy silver with a batch of electrolyte. More is possible if the silver is very clean. That equates to less silver being recycled through the copper bars. Dirty silver will contaminate the electrolyte very soon, and you may find yourself only gaining 100 ounces or so for each batch of electrolyte.

Processing All Waste Material Except Floorsweeps and Polishing Wastes

All waste material that is accumulated from processing should be incinerated well and stored in a drum until such time that enough is at hand to run in the tilting furnace to extract values. I normally run the material once per year. The yield is dependent on the years work, thus no estimate of yield is at hand, but you won't believe what comes from the worthless looking mess you start with. A five gallon bucket of material is a good amount to run, though you may wish to run your material much more often as it is a good source of extra gold and silver.

The incinerated material that is accumulated will have a dark brown color and will vary from very fine particles to lumps. It is a good idea to break up lumps larger than an olive in size so that the material will mix well when the cakes are made. Do keep in mind that the material will spend at least one hour forty five minutes minimum in the furnace and the flame action will mix things well, so don't spend a great deal of time with the lumps.

The method of preparing the waste is to mix it with a fluxing material and water then pour the slurry into forms which will make cakes. The cakes prevent the fine particles from being blown from the furnace when the material is introduced to the furnace for reduction.

The slag from the formula listed below has been assayed for residual gold and found to contain 11.21 ounces gold and 39.3 ounces silver per ton. The gold number is very acceptable for slag that has come from a furnace where lead is not used as a collector of values. I don't know if the silver number is good, but the relative value of the silver is obviously low. A ton of slag

represents a tremendous amount of waste material.

Use either a number 12-S Coors casserole or a number 26-R Coors crucible for your measuring instrument, or something of equal volume.(Approximately six (6) liquid ounces).

Do your mixing in an old ice cream bucket. When the bucket is ready to discard, it can be incinerated and nothing of value is lost.

Use lids from ice cream buckets for the form to pour the cakes. Each batch will nicely fill two lids and after setting they release quite nicely. It all looks pretty bush league, but it works and doesn't cost anything to use. Like the buckets, when the lids are ready for disposal, they should be incinerated for values.

To Prepare The Cakes For The Furnace

(3) parts waste material

(1 1/2) parts silica sand

(3 1/2) parts soda ash

(1/2) part fluorspar

(2) parts borax

(600) ml water

Dry mix the material briefly then add the water. Mix fast as the material stiffens up. The mix should be wet enough to go into a thick slurry. If it isn't, add a little more water. Too much doesn't hurt, it just makes a mess. It isn't necessary to mix very well. Once again, the mixing of the furnace will do the job nicely when things liquefy

Pour the material into two (2) ice cream bucket lids and allow it to set and dry for at least a few hours. I normally pour them one day and remove them the next day. The cake turns quite rigid when it sets well, and releases from the lids easily.

Remove the cakes from the lids and allow them to air dry for a couple weeks if you are preparing them well in advance. It is acceptable to charge them to a hot furnace when they are wet, but the firing time is longer as the trapped water must be expelled. When they are dry to your satisfaction (they will be a light brown color inside when they are broken when completely dry) place them in a (5) gallon bucket, hitting them in the center as you drop them in. They will break into pie shaped pieces, making charging them into the furnace easy. Nine (9) to eleven (11) of them should be broken into a bucket. That constitutes a charge for the furnace, along with somewhere between 1/2 and 1 gallon of old slag from the small furnace, which should be run to extract prills that are likely to be in the slag. The number of the cakes charged depends on the amount of slag that will be charged as well, so balance the numbers so the amount added as a charge is below the fire port when the furnace is up to heat. The cakes at first will be higher than the port, but they melt down to a much smaller volume.

Firing The Tilting Furnace

Charge the furnace with a the used slag (1/2 to 1 gallon) and most of a bucket of the cake material. The slag should go in first and the cake dumped on top. That prevents the old slag from popping out of the furnace as it heats. You will find it is quite active while being heated.

Start the exhaust fan above the furnace.

Turn on furnace blower motor and open the air valve part way.

Turn on the electric ignition.

Slowly turn on the natural gas. When the mixture is right, it will ignite.

Immediately turn off the ignition switch, as it affects the ignition point.

Adjust the furnace to a medium heat, using the air and gas valves. Only experience will teach you what is right. Start with a full flame then adjust it down to about mid-point between full open and off.

When the charge has melted, one can determine if the balance of the cakes can be introduced. They can be dropped in the furnace while it is running with no problems. Keep in mind that the exhaust from the furnace is in the neighborhood of 2600 degrees in temperature, so be sure to use a gloved hand in dropping in the pieces. The small bits in the bottom are best charged to the furnace with the large mouthed funnel, with the furnace shut down to charge them. I usually charge the small bits at the beginning of the next heat, along with the slag, in order to bury the dust and not lose it, though it can be charged during the current run with little loss if the charge is molten.

The firing time for the waste material for the first heat usually takes three (3) hours, as the furnace is very slow to heat up. Remember the material it is lined with is made to resist heat transfer, thus it heats very slowly. Keep an eye on the furnace, and keep it slightly tilted to the front. Look inside and make sure that the charge line, when the charge is liquid, is below the flame port.

DO NOT ALLOW THE CHARGE MATERIAL TO ENTER THE PORT AT ANY TIME .

At first the material will be somewhat active. When the conversion is complete, the charge settles down to a quiet, tranquil mass. Turn up the heat somewhat to superheat the charge. That allows the small bits (prills) to agglomerate and collect in the bottom of the furnace, away from the slag. When the charge changes from an orange glow to a bright yellow, (the furnace wall becomes hard to distinguish from the charge) it is time to pour the furnace. The first heat usually takes about three (3) hours. The next heat normally will take two hours, and I have found it ready to pour as soon as one hour forty-five minutes. In pouring the charge, many small prills like to follow the slag out when it is poured if you try to get the metal from each heat, making quite a job of separating the prills from the slag over and over. I pour off the bulk of the slag and run the next charge, leaving the metal in the furnace until the last charge is run. That way, one only has to go through the separating of prills once. I do this even if I will run the furnace for several days, leaving the metal in until the last.

Position the cone molds on the movable base in front of the furnace, with the farthest mold from you under the spout of the furnace. That way when it is time to move the base, the full cone mold is away from you.

Turn the heat down to almost off. The air should be cut way back and the gas adjusted until there is almost no ignition. No smoke will be liberated so long as the furnace is still burning.

Slowly tilt the furnace, using the hand crank on the end. Don't dump the material. Allow it plenty of time to flow out. Watch to see that no prills are coming out. They will appear as small tiny spots in the slag. Fill the first mold until about an inch from the top. VERY CAREFULLY move the base over until the second mold is under the spout and pour the balance of the slag, stopping before you see the metal start to come out.

When the last charge is run, a mixture of soda ash, borax and a small amount of fluorspar is mixed and charged to the furnace after the slag from the last run is poured. An amount equivalent to about five (5) or six (6) cakes is good. This process liquefies the residual slag and cleans the furnace walls quite well. You will now see the values that have collected in the furnace appearing quite shiny in the bottom of the furnace. Pour off the bulk of the slag in one of the cone molds, and the remainder of the charge in the second, allowing the metal to flow out well. If a good amount of value is still in the furnace, repeat the soda ash, borax, fluorspar treatment a second time. Allow the slag to cool very well before trying to break it up. While it will look to be set on the outside, it may still be molten in the center. I don't break up the slag until the following day. I don't like getting burned. When the slag is cool, dump the mold into a steel drum. You will find a nice cone of metal, along with a few prills.

Check each of the cones of slag that are poured for any buttons or prills that may have been poured inadvertently when the slag was discharged from the furnace. Pay particular attention to the point of the cone. It's purpose is to collect the values, and usually if anything has been poured, it will be there, though prills may be down the side of the cone where the charge was poured. Rerun anything that contains prills, either immediately, or you can save the prill laden slag to run when the sulphide layer that will come from the top of the metal is run.

The Sulphide Layer

You will notice a layer above the collected values that is a dark shiny grey color. It is from the sulfur in the waste material combining with the precious metal in the charge. It has value and must be separated from the cone for further processing

There is a distinct layering of the material, but it is glued on quite well. I use a chipping hammer and beat the hell out of it. Make sure you wear eye protection as the pieces fly most everywhere. Sweep up all the material you chip off and charge it into the crucible furnace along with any prills and slag that contains prills. Get it molten and introduce some scrap steel to the charge. A couple pieces of rebar, angle iron or channel iron can be used. Make sure the piece(s) you introduce to the charge are DRY. . Heat them over the furnace port before putting them in. Cold metal has moisture on its surface and an explosion will follow anything dropped in cold. The pieces should be long enough to retrieve when the work is done. Allow the furnace to run for about 20 minutes or so. The sulfur in the charge has a greater affinity for iron than precious metals, so you will find that the metal in contact with the charge is eaten up and the metals of value are liberated. If you don't have a slag cover already, add a small amount of soda ash and borax. Remove the iron before you pour the charge. After pouring the charge in the cone mold, you will find that the texture of the sulphide has changed. It darkens considerably, and gets a much finer grain to it. If there is any doubt about it containing more precious metal, run it a second time. You will find that each time it is run a much smaller amount of metal will be found under the resultant sulphide layer, if any.

Gold comes out right away, along with most of the silver. If a small button is found the second time, very little gold will be found in the button.

When all of the metal has been collected from the furnace operations, charge it all into a #8 crucible and melt it. Pour the metal into the stainless steel water container to pelletize it for processing. Use normal refining procedures. You will find a lot of silver, gold, and a good showing of the platinum group.

Slag

The slag that remains from the furnace operation has gone as far as you can take it. In order to remove the residual values, it must be processed with litharge. That is beyond your capabilities, and it should be avoided anyway, as the fumes from this operation are quite hazardous.

Save the slag in large drums. When you have what you think is enough to sell, it should be offered to: G D Resources Inc.

450 E. Glendale Avenue

Sparks, NV 89431

1-(702)-358-9229

Fax 1-(702)-358-9275

I wouldn't offer much less than a couple drums, as they have minimums.

You may want to negotiate on the platinum group metals the slag contains. If it isn't mentioned, you will probably not be paid for it. It also may not be present in enough quantity to worry about. I have no history on this. A good idea is to submit the slag along with the waste material from the filter press at the same time. The total of the two lots may be included as one in

their eyes and you would end up with more of the platinum group, bringing up the amount of platinum group submitted. They will pay for it for sure when there is enough.

Materials

To obtain the necessary material for running the waste material, the following sources can be used.

Borax. 5 mol borax should be purchased. It already contains some water, but it will appear dry to the eye. It comes in one hundred (100) pound bags.

Soda ash. Specify dense soda ash when buying. It comes in both fifty (50) and one hundred (100) pound bags. It's a lot easier to handle the fifty pound bags.

The borax and soda ash can be purchase from any of the local chemical companies. Van Waters & Rogers, Thatcher or Great Western are all sources, but there may be others. It doesn't hurt to check prices, as they vary.

Fluorspar I got from Great Western Chemical. Talk to Marjorie Morgan. She has a customer that uses it. The customer buys it in large quantities. She got a few bags of it for me from that customer when I needed it. One need buy only one or two bags as very little of it is used in the process.

Silica sand can be purchased from Standard Builders Supply. It comes in one hundred (100) pound bags and isn't expensive. (About $6.00 per bag). It is used with the charge to protect the lining of the furnace. It also helps form a good slag. It doesn't matter what mesh is used. I have used 30 and 70 mesh with equal results.

Filter Papers

To select the proper filter paper for your task, refer to the simple guidelines below. There is no good reason not to deviate from the recommendations. Treat the recommendations as such, just recommendations. There is a reason you will use the papers in the fashion suggested, but there are also reasons to depart from the recommendations. Make a judgment and go with it when you have cause to do something different from a given recommendation.

We will discuss only four (4) different grades of papers, all of which you have in your supply. There are more papers on the market, but for our purpose, these cover any situation that may occur.

The Four Types of Paper

S & S Sharkskin

VWR (cheap #1 Whatman equivalent)

Whatman #2

Whatman #5

Selecting the Proper Paper

S & S Sharkskin

Use the sharkskin paper for such things as the mud from floor sweeps and polishing wastes, after the mud has been rinsed in water and you are trying to get the last of the gold chloride solution away from the mud for evaporation. Sharkskin paper is very tough. It has good wet strength. Solutions that are somewhat acidic can still be filtered with Sharkskin. None of the other papers have any wet strength. The negative side of sharkskin is it isn't very retentive. It will filter very rapidly, but it

can let small amounts of dirt through. For the purpose we use Sharkskin, that isn't a problem, as anything that goes through the sharkskin paper will eventually get filtered again before precipitation.

VWR

You will filter the black mud from the stock pot with the VWR filter paper. It is not expensive to buy. The VWR paper is similar to Whatman #1. It is a moderately retentive paper, but lacks wet strength. It is a fairly fast paper to use in a case where you want to filter something and retain the bulk of the fine particles it contains. You would choose this paper if you were refining a batch of eye glasses to filter the gold residue after digesting everything in the first operation (nitric acid dissolution). The collected values from running eye glasses have to be incinerated after the first operation then boiled in HCL, thus the first filtration. If you select this paper and it tears, go to Sharkskin instead. It doesn't have much strength, so the material you are trying to filter can't have much free acid in it as the acid will destroy the paper and it will break through.

Whatman #2

You will use Whatman #2 for filtering gold solutions that are headed for precipitation. Whatman #2 is also good for buchner funnel filtering (vacuum filtration). When you have washed gold that is re-refined, a Whatman #2 in your buchner funnel is adequate for filtration before drying, as the gold particles are very course and won't go through the filter paper. Whatman #2 is quite retentive, allowing only the finest of particles through the paper. A Whatman #2 is good for filtering the silver mud that comes from your copper bars. You have some #1 Whatman papers for some of your buchner funnels. They too will do nicely for filtering small lots of the silver mud. Speed wise, Whatman #2 is reasonably fast.

Whatman #5

The only use of Whatman #5 is for filtering gold chloride that is being filtered in the second refining. USE ONLY FOR RE-REFINING.

The exception is in the smaller sizes that will fit the buchner funnels you have. Whatman #5 is stronger and more retentive than Whatman #2. It is also much slower as it will retain almost anything solid. Whatman #5 is very expensive as filter paper goes. There will be times when you try to use a Whatman #2 in vacuum filtration and it will either perforate or allow fine particles through. If that happens, go to a Whatman #5. It will usually prevent either situation from happening, but at the expense of slower filtration. You will use either a #2 or a #5 Whatman paper when you filter any of the platinum group metals after precipitation from their respective solutions. Whatman papers are imported from England and are the most expensive paper you will buy. There is no paper made in the States that will do the same job as either Whatman #2 or Whatman #5. They are clearly the best filter paper on the market for the work you do, and they are worth the money.

Processing Carpet

Carpets that have come from stores or shops that have benches located over or very near them can be very profitable to process, but care must be exercised to insure that the carpet in mind has been exposed to traffic areas directly linked to manufacturing. If a store has done nothing more than polish (buff) jewelry, chances are very good that you will invest a few days work for nothing. Without traffic related to a bench, it is highly unlikely that gold will be found in a profitable amount in carpet. Likewise, if the carpet in question is not of the proper consistency, not much should be expected from it. Thick loose woven carpets, such as shag, are very good. A carpet resembling felt naturally wouldn't hold much gold. Good sense should be the rule.

Grading Carpet

Wool carpets are very difficult to process because they tend to not incinerate well. Avoid them if at all possible. Synthetic carpets are normally processed easily, though you will see differences in them. Some are easier than others, but they all run well.

To make a decision to run a carpet is somewhat difficult, as there is no sure way to determine if carpet has enough value to justify the time and expense to process it. The only thing you can do is take a sample from an AVERAGE area and see if it contains values. Don't do your checking for gold under a jewelers bench. For sure, you will find gold there. Check other areas to see how widely spread the gold is. A quick visual test can be performed by cutting out about a square foot area and bending the carpet back to back and see what drops out. If you don't find any fine gold particles (filings), there is a pretty good chance the carpet will be a loser and shouldn't be run. You will have to make that decision, and as you see more carpets, you will feel more confident in doing so. If not much is found in an average area, it might be a good idea to take what is under and near any manufacturing benches and leave the rest. Benches should not be confused with display counters. The exception to that would be if the bench person serves the counter, the rear area that the bench person occupies could be loaded with gold while the other side (customer side) would be totally absent of gold. Use good judgment when doing your investigation.

If you determine a carpet might be worth processing, try to take carpet that has come from work person traffic areas only. It doesn't make sense to take carpet that has always had a display cabinet on it, as there is no way that anything could have gotten into that particular area, and every square foot saved makes a good deal of difference to you in the long haul. Carpets are a lot of work and there is no reason to add to that burden for no gain. Make sure that the carpet you start with has value. Likewise, it makes no sense to take a carpet that has been on the customer side of cabinets and work people never walk on them. Keep in mind that work people get somewhat covered with gold particles in the process of doing their work, and it drops off of them as they walk back and forth, to say nothing of what sticks to shoes and gets rubbed off as one walks. Traffic areas are good collectors of gold if there is carpet to absorb it.

Normally if a carpet has been down for some time and it contains values, you will find the gold has gone through the carpet and will also be in the pad. If that is the case, make sure you take the pad as well, though to take pad that has nothing in it is not a wise move. Keep in mind that you will handle the material many times, so don't add to your burden and expense by processing things of no value.

Incineration

Carpets are refined, like most all other waste material, by starting with incineration. It is a good idea to get any carpet you will handle reduced to small rolls that can be handled easily. Always clean up and process the dirt that falls away from the carpet as it is cut up and rolled. It will contain a good amount of gold.

The incineration process starts with burning the carpet in a half 55 gallon drum that has a fire built under it. Scrap wood is used for the fire unless you care to use a propane burner, which can get costly, but is more convenient. This operation is almost impossible to do near civilization, as it resembles a burning tire. Plenty of black smoke comes from incinerating carpet, as most synthetics are based on oil, and the end product becomes oil before being reduced to ash by combustion.

Roasting the Ash

Ash that is returned to you by incineration will have reduced the carpet from a truck load to several gallons, but the work is not done. As getting oxygen to the carpet and maintaining a temperature over 1,100° for complete combustion of carbon is difficult, you will find the incinerated carpet will contain material that is not completely incinerated. No matter how long carpet is left in the drum in which it is incinerated, will it be complete and ready for acid. You must roast it at high temperature. The smoke is not only obnoxious, but is toxic.

To incinerate carpet without breathing the resultant smoke, set up the very small furnace in the mouth of the fume hood, or get a hood (canopy type) and blower assembly set up in another area so you don't tie up your fume hood for hours on end, as the roasting process takes a lot of time.

The operation is set up with a thin stainless steel plate (1/8") set on the furnace with 3/4" asbestos spacers holding the plate above the top surface of the furnace. It is easy to see the idea is to heat the plate to redness and continue the incineration to completely consume the carbon remaining. The test for this is color. You will find the ash that you get from incinerating will be grey to black in color. After proper incineration, the color should be a light grey to purple in color. The presence of a pink

to purple tint is a good sign that the carpet will be high in value, as it is finely divided particles of gold that give the color to the ash. These particles normally come from buffing.

The furnace is lit and allowed to run continually through your work day. A layer of carpet ash is placed on the stainless plate and allowed to cook. You will notice a color change on the edges first. Stir the material occasionally using the table spoon that is welded to the long steel handle. The long handle keeps you away from the intense heat. Having little or no light over this operation is good, as you want to look for little bits of carbon that are burning. You will see little hot spots in the ash as you turn the material over each time. Do this until they are no longer visible. Make sure the ash has changed color. Don't take ash off the plate that is still black in color, as for sure you haven't burned off the carbon.

The ash in this process will shrink in volume, but not a lot. You might expect at most a 10% decrease in volume in this operation.

Screening the Ash

Once again you will do an operation that has become all too familiar to you. Screening the ash is the next step. You have a lot of ash to deal with, and you might want to rough screen it rather than go for fine screening, as you will spend a great deal of time on this otherwise. It is important to screen the ash, as large pieces of gold have a way of getting into carpets and never getting recovered. Further, you should expect to find a few diamonds. After screening the ash, be sure to go through it with a magnet, as a lot of iron is accumulated in carpets. The iron removed will go nicely in the stock pot, allowing you to make a recovery of any material of value that might hitch hike with the iron.

Dissolving the Ash in Hydrochloric Acid

It is here that you will finally get the ash to a volume that is reasonable to handle. The gallons of ash that you start with will be rendered to perhaps at worst a couple quarts.

This operation is a real pain, as the ash is basic and reactions are fast and violent. I concluded that the easiest way to process the ash is to fill the large handled pyrex cylinder about two inches deep with hydrochloric acid (HCL) and water (about 25% water) then slowly introduce scoops of the ash to it. You will have the pyrex cylinder in the mouth of the hood, as the fumes from the hydrochloric acid will be a real problem for you otherwise.

The reaction from combining the ash with the acid is instantaneous and violent. Heat is liberated with this process, and the cylinder will get very hot. Stir the slurry as you introduce the ash, and go slowly. If you have a fiber glass rod, use it instead of a glass rod. It will last much longer. Glass rods tend to break in this operation. At first there will be violent evolution of gasses, but that slowly changes as the acid is consumed. Unfortunately, along with the slower evolution of gasses, the slurry starts to boil over on you. Here is where the skill of the operator takes over. You will introduce the ash and it will start to boil up and it never wants to stop. Adding water slowly helps keep temperatures down and slows the reaction some. If you stir and add slowly, you will minimize the problem, but it never goes away until you have used up the acid. At that point, you aren't dissolving the ash, so you aren't doing any work. When you feel you have used up the acid by continually adding ash, check to see if you have by adding more acid. You will have reaction again when acid is added if that is the case. I used to add HCL by using the 5 gallon container with the spigot. Allow acid to run in to see if it is doing any work. Good sense will tell you that you have gotten the container to the point where you don't want to add any more acid or ash and it is time to empty the container. For me, usually by the time I had added the second amount of acid and used it up, I preferred to empty the container and start over. Make certain that you stop with some unused acid remaining, as there are particles that will slowly break down after you have stopped introducing ash. I allowed about a half hour of soak time for that to take place before I went to the next step.

At this point, you will see the results of your work, as the gold that is contained in the ash will now be in a film in the bottom of the cylinder. You can view the gold by pulling the container over the edge of the counter and shining a flash light up through the bottom. You will see a nice layer of gold if there is any contained in the ash.

After the slurry has had the soak time, add water to the slurry until the water level is just below the handles. In that way, you

wont have values sticking in areas that won't allow particulates to settle to the bottom. Be certain to stir the water well. The idea is to dissolve all solubles and get them in solution in the water so you can get rid of them.

In order to facilitate getting this operation done in less than the next month, I usually would allow the cylinder to settle for an hour or so, then siphon off the solution into one of the 16 gallon polypropylene cylinders. Having done that, add water to the mud again and stir well and allow to settle over night.

After allowing the mess to settle well, siphon off the solution once again into the 16 gallon container. The objective is to get the solids contained in the pyrex cylinder into a large beaker for storage until it is time to extract the gold. It is a good idea to pour off the light solids and keep them separate from the gold filings in the bottom. The light particles that pour off easily contain gold as well. It is here that the polishing waste tends to accumulate. That is the reason you allow the large polypropylene cylinders to settle for a couple days before siphoning off and discarding the solution. In the bottom you will always find a layer of fine mud which contains gold. Gold that you won't be able to see, but will be extracted when you introduce aqua regia.

Repeat the above until you have processed all the ash. Keep everything that is solid for further processing. After allowing the solutions to settle well, discard them. What you are getting rid of is the dissolved ash, and hopefully you have retained all the gold in the solids that remain.

When you have gotten all the fine solids (not the filings) into a 4000 beaker, introduce enough aqua regia to dissolve perhaps three ounces of gold. Bring it to a boil and allow it to cook for a short time. Look at it from the perspective that if there were filings in the bottom, which there will be, the digest time should be long enough for them to go into solution. When that has been accomplished, allow the slurry to settle well. You will use the solution from the fine solids to dissolve the filings which you have held in another beaker. In that way, you will have gotten rid of the bulk of the solids that you end up with and not have gotten the solid waste saturated with the pregnant aqua regia solution. Good idea where honesty towards your customer is concerned. Needless to say, you will wash the solids with water once, just as you do floor sweeps and polishing wastes, and add the solution to the batch.

Once you have the gold extracted from the mud, treat the mud the same way you would floor sweep and polishing wastes. Dry the residue and add it to your waste material for processing in the future with cyanide and final disposal by selling to a major refiner. This material will never be rendered valueless by your work.

End your work by processing the solutions the same way you process all other gold chloride solutions.

Settling With Your Customer

Regal, in the past, charged 50% for processing carpets, and that fee is a good guideline for you to consider, as the typical carpet will not yield a great deal of gold, and you will have spent about a week processing it. Distribution of the gold should go as below:

The person that incinerates the carpet gets 15% of the gross yield.

The person that roasts the carpet ash gets 10% of the gross yield.

The person that refines the ash gets 25% of the gross yield.

The person that supplies the carpet gets 50% of the gross yield.

Clearly, the fee for refining is 50%, which is not unreasonable for carpet, considering you start with several hundred pounds of material to get down to the gold. Major refiners charge something like $2.00 per pound to receive such material, plus more to extract the gold. The 50% fee is reasonable.

Needless to say, this is your operation. I suggest to you that you start with the guidelines set forth in this flow sheet. As you learn more about your work, you may or may not find better and faster ways. Should you learn something that is not included and it works, certainly use the process. I developed this system and stayed with it because it worked. That is not to say that there aren't better ways to run carpet. It was the best I found, but it may not be the best. Make decisions and improve the system as you gain knowledge. That is what I did.

Processing Eyeglasses

Eyeglasses that are marked as gold filled are very worth running, particularly when the mark reads 1/10-12KGF. That tells you that the original gold content of the eyeglasses was 5%, which in terms of low grade gold scrap, is very good. Typical yield from such glasses runs about 3 1/2%, as the gold surface is what is worn away when eyeglasses are worn.

One begins the process by breaking out all the glass and clipping plastic. It has been my experience that plastic that covers thin metal rods that make up the side rails of eyeglasses normally has no gold, but I suggest that you test them with nitric acid until such time that you are comfortable with what you are looking for. Early wire frame glasses will have the flexible round piece that goes over the ear covered with a flesh colored plastic and the interior is what looks like a very fine spring covered with gold. They are always gold filled, so don't throw them away.

You will find that aluminum is used as trim on metal frame glasses in some cases. Aluminum that gets into solution with gold creates filtering problems for you, so if you find aluminum while you are removing glass and plastic, get rid of as much of it as you can. Later in the operation you will have an opportunity (you will read about it later in this operation sheet) to remove aluminum that gets by you, but be sure to have it all out of the system by the time you dissolve the gold.

Hinges are known to come with or without gold content, so I ended up running most all hinges unless it was very clear that a particular hinge had no gold, which on occasion you will see. Hinges that are not gold normally will be what resembles white gold, but instead of being white, they will be covered with a green film, which is a strong indicator of nickel. Many of the hinges will be white in color, and they are covered with white gold.

After you have broken down the eyeglasses, the next operation is to incinerate them. Naturally this process would have removed the plastic you clipped earlier, but plastic makes lots of toxic smoke, so the idea is to minimize what comes off. You want to get along with your neighbors, and this helps a lot! The eyeglasses are incinerated directly in the very small furnace.

Incinerating Eyeglasses

This operation will produce a lot of toxic smoke and gasses, so be sure you are operating either under an exhaust hood or the furnace is set up in the mouth of the fume hood.

Start by dropping in a handful of the broken up glasses and turning on the gas and blower then lighting the furnace. The small furnace doesn't like to stay lit when it is empty until it is hot, so if you start off with some plastic in it, it will use the burning plastic to support combustion until the heat comes up. Regulate the gas so the flame is burning inside the furnace, not out of the top as it likes to do. Using a metal rod, stir the glasses to expose all parts to the flames as they burn down. As they incinerate, all will turn red hot and the soldered joints will let go and everything turns into a small twisted mass of metal pieces. Continue to add the eyeglasses until all have been incinerated. If the furnace starts to get too full, drag out some of the incinerated metal parts.

Everything in the furnace should be processed for gold content, so empty the furnace by tipping it upside down after it has cooled down enough to handle. I used to let it cool until the next day.

Dissolving the Base Metals

This operation is where you will have some problems, no matter how careful you get, and the operation itself leads you into a sense of complacency, because the reaction I will discuss now will not be apparent. You will be inclined to suspicion that I

have mislead you. Don't fall into that trap, for this operation, guaranteed, will boil over on you, and it will do so in a matter of seconds, even when you have only a half inch of material in a 4000 ml beaker.

Our objective at this point is to get rid of the 95% of metal that isn't gold. Like other operations, you use nitric acid (HNO3) and water. I start with a fair amount of metal, perhaps about a half beaker, using the 4000 ml beaker mentioned above. At first the reactions will happen fast, so no heat is used to start. Pour about a half liter water on the metal then about that amount of nitric, only pour a little of the acid in slowly and allow it to work before pouring in more. Do this until you have used up the acid and then put it on a burner and heat it until you don't get any brown fumes coming off. At that point, you have used up the acid. You will keep all solution from this operation as the gold will come off not only as small particles, but in almost colloidal particles which are in suspension in the solution. You must allow time for them to settle. The brown to purple mud that accumulates is the gold, along with iron oxide and other things that may or may not have value to you. It is the mud that you are after in the end.

Pour off the solution from the operation into a glass container, diluting it with about an equal part of water. You don't want the solution to be dense. Don't use plastic, as the gold tends to stick to it and you will have a hard time getting it all off for the next operation. Allow the solution to settle until it is free of flocculence. You want to have a nice layer of mud in the bottom before you handle this solution. Don't attempt to filter it as the solution tends to be of such a nature that it won't filter well, if at all. Allow gravity to do this operation. Keep in mind that running eyeglasses takes time, and you are paid more for doing them.

As you dissolve the copper based alloy from the glasses, things will go nicely. As the copper is removed, the problems begin. The nickel alloy that is used in a good number of glasses doesn't start to dissolve while the acid is cold, or even quite warm. Here is where it starts to boil over. You will reach a point where you think that what is left is gold because acid does nothing when you pour it on. Heat the beaker and don't leave it unattended. Watch it carefully. As the heat reaches the critical point, you will see some action begin on the metal. A slight bubbling is noticeable, which continues to grow in intensity. A critical point is reached where within a few seconds, the solution froths up and out of the beaker. To control this reaction, remove the beaker from the burner and introduce water. The amount you introduce should be enough to stop the frothing but not too much to cool things down very far. When you have enough water to slow down the reaction, put the beaker back on the burner and watch it closely, as the same thing will happen until you either consume the acid or dissolve away the metal.

You will repeat this operation until all pieces of the metal you started with have turned to mud. The exception will be that some parts of eyeglasses appear to be made of titanium, like the bridges mentioned earlier. You will find these pieces refuse to dissolve. If you boil them long enough in nitric, they will release the gold layer that is attached to them. The surface of parts like this tends to turn rainbow colors, though I have seen bridges that are a dark yellow brown color after the gold has released from them. Testing will tell you where you stand. Nothing but experience will let you run eyeglasses easily.

When you have reached the point where all pieces have broken down, boil hard in nitric the last of the material that still remains in the beaker. I usually would boil for about an hour. That gives small pieces time to totally break down. Don't be concerned that the gold turns to mud. The way you run this material that isn't a problem, and in fact it is to your advantage.

When all the solutions have settled properly, siphon off the predominantly copper based solution and introduce salt to it to recover the silver that is contained in it. You will find a fair amount of silver comes from eyeglasses, as when the gold breaks down as, it does in this situation, virtually all of the silver contained in the gold is liberated. Further, the glass frames are assembled by soldering, thus there is a fair amount of silver from the solder joints. Your objective here is to separate, as much as possible, the solution from the mud. Combine all the mud in one beaker and ad water again, letting it settle once again. After you have concentrated all the solution into one beaker and allowed it to settle again, siphon off the solution that you can get without taking any mud with it then set a filter (the same paper you use to filter the concentrated stock pot waste) and filter the balance, washing the mud into the filter as you go. At first you will have a solution that allows some of the gold through, which will have the appearance of fine purple particles or purple solution. Run the same solution back through the filter until the discharge from the filter is clear of purple color. The solution coming from this should be blue in color with no particulates settling in the catch container. I don't recommend the use of a buchner for this operation, as it tends to pull gold through. Allowing gravity to do its job works well, and you will usually have things done in a day, or over night at worst.

Processing the Mud

When all the mud has been filtered, with the material in the filter slightly dry, incinerate the mud along with the filter paper. Burn it much the same way you do any other material. It is important to heat it until you have discharged any residual nitric acid, which you will see coming off as the familiar brown cloud. If you don't get rid of the nitric, you will lose gold in the next operation. Keep in mind that you now have all the gold concentrated in this mud, so its value is very high. Try to not lose it to dusting and spilling.

When the incinerated material has cooled, the next step is to remove things that are not gold. Start by screening the material through your fine sieve. Because aluminum is not soluble in nitric acid, it is here that you will have the opportunity to remove any other aluminum, as it will be left behind as a nice white clean looking metal. You won't have any problem identifying it. Any aluminum you remove should go into your stock pot as it may contain bits of gold, and aluminum works very well in the stock pot. The screws should be discarded, but only after rubbing them very well in the mortar and screening them again until you don't see any more gold coming from them. The other thing you will find is the stainless steel object that comes from the interior of the nose pads from glasses. It will be a thin piece, slightly bowed, about 1/4" long and tapered on each end, 1/8" wide in the center, with a hole in it. Remove these things and rub them in the mortar, screen them again then discard them. The stock pot isn't a good place for the stainless pieces, the suspected titanium pieces nor the screws. Throw them away.

When all of the screws and other material have been removed, you should have nothing left but what has gone through the sieve and the small amount of material that didn't break down totally. It can be included with the dirt for the rest of the operations. If you find large pieces that are gold on the surface but don't have the interior dissolved completely away, you know you should have digested them longer in nitric (that doesn't include the parts that appear to be titanium). A small amount of this stuff won't hurt you in the next operations, but the less the better.

Hydrochloric Acid Wash

This operation is very important, as if you don't do this one, you will have a terrible time filtering the gold chloride that you end up with after evaporation. Put the dirt (gold) and remaining small pieces into a beaker, using one that allows room for acid and lots of water, particularly after you have boiled the mud and have added a large amount of water to allow the mud to settle again. Using a generous amount of hydrochloric acid, (cover the mud by perhaps a half inch) and water, boil the mud for about fifteen minutes. What you are doing here is dissolving more things that you don't want in the gold. The things you get rid of are what give you trouble filtering. You will notice the gold mud turns to what looks like fine gold sitting in the bottom, which is what it is. Along with the gold particles you will see a lot of mud that is pink to purple in color. Naturally, it is gold as well. The interesting thing that happens here is after you have washed the mud in hydrochloric, it settles very fast. Having removed the beaker from the burner after boiling for about fifteen minutes, add water until the beaker is full and stir well, getting all the dissolved material well stirred in. The idea is to wash away the solubles. Notice that the solution turns milky when you introduce the water. That is normal, and it is caused, I think, by the lead that is in solution precipitating. You will deal with any lead that ends up in the gold in the usual manner, by introducing sulfuric acid to the gold chloride when you are evaporating.

You will do the wash operation perhaps two times, only one if you have a small amount of mud in a large beaker. I liked to do it until the wash water was pretty clear of color, as the less you drag through the operation the cleaner the gold in the end, and the easier the gold chloride filters.

You are now down to gold that can be processed the same way as filings that have had the nitric wash. Dissolve the mud and from there treat the solution the same way you treat any other gold chloride solution. The normal fee charged for processing eyeglasses when I ran the operation was 25%. As the glasses I have provided you were of lower quality, I would like you to take 50% of the values for your work. If nothing else, you will make a dollar and gain a valuable experience in processing eyeglasses. You won't learn this one without doing it, and the material I have provided you is low enough in quality that any losses will be minimized as they weren't 1/10-12K, though they were all gold filled.

If You Have A Boil Over

Not a lot can be done to prevent the occasional boil over. You will deal with it by wiping down the fume hood with paper towels. Incinerate everything that comes from the hood, then start over with the dirt and nitric acid. You will be put out a good deal work wise, but you won't have lost much if any of your customers material. Once you have gotten the dirt digested and back to the same position you were in before the boil over, combine the mud and get on with things again.

Markings as low as 1/30-10KGF can be expected where eyeglasses are concerned. The marking is found on the bridge piece, along with the side rails of the glasses. You will also find marking that read differently than those mentioned here. Some of them are displayed as four digit fractional numbers. Make sure that you learn to understand the meaning of these markings so you don't spend a great deal of time running material that isn't worth the time and material invested, and also so you know what to keep for refining should you encounter them in second hand stores. If you want to buy eyeglasses, you don't want to pay more than a dollar per pair if they are marked 1/10-12KGF. Typically, they will average about $3.00 in gold per pair, but you will have a great deal of time invested in processing them, along with a fair amount of acid. Try to purchase eyeglasses for fifty cents. That is a good price for you to make money. The only problem with eyeglasses is that the source has slowly dried up because of the value of gold and changes in styles. You aren't likely to run into a large number of them, though if you know any people that deal with them (like opticians), they may have large numbers of them. It typically takes about 160 pair to return an ounce of gold.

Silver Chloride

The silver chloride you accumulate in doing your work will eventually get in the way and you will want to reduce it to elemental silver and get it back in the system. This operation is simple, but takes a little of your time.

It goes without saying that you want the silver to be as pure as possible when it is converted, as the cleaner the silver going in to the silver cell, the longer you can expect your electrolyte to last.

Begin processing your silver chloride by getting it into the large handled pyrex cylinder. Silver chloride is peculiar in that no matter how carefully you try to handle in, it likes to move in plops and splashes. It is a good idea to stir it vigorously with some water then try to pour it into the large cylinder. Keep as close to the bottom of the cylinder as possible to prevent losing the silver chloride by splashing out, which it likes to do. After you have transferred the chloride to the cylinder, your work is now to wash it until the wash water is clear of color, as any blue left behind is copper and it will be included in the silver.

At first, the chloride will not settle very fast after you have added water to it and stirred, but each time you do this operation it will settle faster. The first two washes or so can be with cold water, but eventually when it likes to settle rapidly, you should wash a couple times with very hot tap water. The idea here is to dissolve any lead nitrate that has been carried over in other operations. Lead nitrate will dissolve in hot water and precipitate by itself as the water cools, so your objective is to get it into solution and siphon it off before it can precipitate from the water again. The reason you wait until you have washed the chloride in cold water a few times is that at first the chloride stays in suspension and you tend to lose some of it to washing. By the time you have washed it a couple times, that problem goes away.

Converting Chloride to Silver

There are a few ways one can convert the silver chloride to metallic silver, but the method I found easiest, fastest and most economical is to do the work with aluminum waste material. The idea here is to use scrap aluminum such as aluminum extrusion or aluminum plate or sheet. Try not to use very small items, as once the silver chloride has been converted, you must remove all the remaining aluminum so as not to contaminate the silver with aluminum when it is melted. Also, try not to use pieces that are too large, as when you stir the batch as it is working, you can break the cylinder if you are a bit reckless. It is a good idea to use a fiber glass rod instead of a glass one to stir.

Begin this operation by covering the now very well washed silver chloride with a 10% HCL (hydrochloric acid) and water solution. Bring the solution to about a half inch above the top of the chloride, which should still be in the large pyrex cylinder. This operation will liberate a tremendous amount of hydrogen gas, so be sure you have the cylinder either in the hood, outside

where the hydrogen can't accumulate, or under an exhaust system of some kind. Don't take chances with hydrogen gas. It is extremely explosive and not too forgiving.

Introduce scrap aluminum to the cylinder by lowering it into the chloride. Be certain it is covered by the chloride as it takes intimate contact with the aluminum to convert the chloride to metallic silver. You will see the process begin almost instantly with the silver going quite dark, even black at the point of contact.

After the aluminum has been in the cylinder for a short time, the heat will come up and eventually the slurry may even boil. A lot of water is lost to evaporation as the slurry continues to heat, so it is a good idea to add a water occasionally to replace the amount evaporated. Keep the solution rather thin so it will stir well. You will see what I mean the first time you encounter the operation.

As mentioned above, the conversion from chloride to elemental silver takes place upon contact with the aluminum, so obviously it is a good idea to continually stir the entire mess until all of the chloride has come in to contact with aluminum.

When Is It Finished?

As the chloride converts (you actually have liberated the chlorine from the chloride, giving off not only chlorine but hydrogen) to silver, you will notice a change of color that accompanies the transformation. Hoke refers to this silver as cement silver, and the name fits very well in that the resultant silver resembles Portland cement in both color and texture. The silver is very slippery and difficult to handle once it is converted. Until it is dry, it is a real pain to work with.

Keep stirring the slurry and allowing it to work until you don't see any white specks in what used to be the silver chloride. When the chloride has totally converted, there are a couple indicators to look for, the color being the first one. Secondly, until the chloride has completed converting, it tends to fuse to the aluminum. When the conversion is complete, you will find that the aluminum will wash free of silver readily and have a clean white surface. I suggest you check the aluminum before the operation is finished, then again when it is so you will see the difference.

When you are convinced the chloride has been totally converted, remove the aluminum pieces from the slurry, washing them clean with water as you remove them.

Aluminum is digested in this process and very small pieces may be left behind. They will easily be identified by the presence of bubbles. Simply allow the slurry to stand for some time and look for a stream of bubbles coming from the slurry. The bubbles are a result of the bits of aluminum being digested by HCL. In the process, hydrogen is liberated and it is the stream of hydrogen that you will see. Dive in with a gloved hand and pick up the solids where you see the bubbles. Careful looking will show you the piece of aluminum, which you should remove. Save all the removed aluminum for use the next time you reduce your silver chloride.

Washing the Cement Silver

Once the aluminum pieces are removed, it is time to clean the silver and wash it to remove traces of residual aluminum that is in solution. Start by adding about a pint of HCL to the slurry and stirring well. The idea is to dissolve anything that remains in the way of traces of aluminum bits and to be certain that the solution stays strongly acidic so when water is introduced nothing is precipitated that you want to discard. Allow the HCL to sit for fifteen minutes or so after stirring it in well, then, if no action is observed, fill the handled cylinder to the bottom of the handles with tap water and stir well. You will now allow the silver to settle very well. Keep in mind that anything in the way of solids is now silver.

The resultant solution will have some weird characteristics. It doesn't appear to want to settle, and after a day it will still look that way. Careful examination will show the solids are nicely on the bottom, but color wise the solution looks about the same as the solids. The solution will have somewhat iridescent qualities and appear milky and you will swear that silver is in suspension. Careful settling and siphoning as suggested will insure that you aren't throwing away anything of value.

Carefully siphon off the solution, staying a safe distance away from the bottom, as the silver is very fine and will readily be drawn into the hose. Interestingly, the solution you are discarding is virtually impossible to filter. It clogs even the coarsest filter paper almost immediately, so you have no alternative but to let gravity do your work. You will need about three to four days of washing to get the silver where you can filter it, which eventually you will do. Each time you wash the cement silver the wash water will come clearer. When you think the solution is clear enough, you will filter the cement silver in a buchner in order to get it dry enough to handle.

Filtering

Once the cement silver has been washed nicely, get it into the large buchner funnel, using either a #1 or #2 Whatman paper. It isn't necessary to use the finer papers which cost more and are slower, as while the silver is quite fine, it is coarse by particle standards. Handle the cement silver much the same way you do the silver that comes from silver recovered on copper. A final wash and tamping it down in the buchner is in order. You will find the silver is very sticky while it is saturated, but as it dries it begins to handle much better. Run the filter until the silver is quite dry, then get the silver cake into an evaporating dish and slowly dry it on a low flame in the method you are now familiar with. This silver, when dry, will melt quite nicely. Don't flux it until it has gotten up to a molten state, as, like the silver recovered on copper, if you flux it earlier, much is absorbed by the flux. You will flux the melt with borax only. DO NOT USE SODA ASH! You don't want to reduce any contaminants in the silver, you want to remove them, which borax does fairly well. After pouring the silver button, clean it like usual and remelt it to cast an anode for the silver cell. The filter paper normally will retain a good deal of silver. I found it was good to put it in the bottom of the crucible before melting the silver. The carbon left behind does no harm and you recover all the silver from the paper.