Butler Pocket Handbook of Blowpipe Analysis

7/29/2019 Butler Pocket Handbook of Blowpipe Analysis

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POCKET HANDBOOKOF

BLOWPIPE ANALYSISDESIGNED FOR THE USE OF

STUDENTS AND PROSPECTORS WITH THE IDEA OFMAKING ORAL INSTRUCTION UNNECESSARY

BYG. MONTAGUE BUTLER, E.M.Dean, College of Mines and Engineering, University of Arizona

FIRST EDITION, CORRECTEDSECOND THOUSAND

NEW YORKJOHN WILEY & SONS, INC.

LONDON: CHAPMAN & HALL, LIMITED1916


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Copyright. 1910.BY

. MONTAGTIE BUTLER


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PREFACE

THIS little book was written, primarily, to satisfythe demands of those instructors who have beenusing the author's Pocket Handbook of Minerals asa text-book for courses in mineralogy. While thereis no doubt that a thorough knowledge of the physicalcharacteristics of minerals should be the end soughtby all teachers and students of this subject, it isoften desirable to be able to fall back upon othersimple tests in corroboration of conclusions reachedby observation, or when studying an unfamiliarmineral. For this purpose, blowpipe analysis isvery satisfactory, since the necessary implementsand reagents are comparatively few and simple andmay be so selected as to be portable.While there are many works on this subject,

they are either too comprehensive for the purposefor which this is intended, or else form merely anintroductory chapter to a work on mineralogy. Inboth cases, their purchase entails a needlessly highexpense, and their directions and statements areoften so vague and incomplete as to require continualexplanation by an instructor.

iii


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iv PREFACENo originality is claimed for the tests themselves

as given in this pamphlet; they are the same as areincluded in all books on the subject, and as havebeen taught in the Colorado School of Mines foryears by Professor H. B. Patton. Such modificationsand additions have been made, however, as experi-ence has proven desirable. The text and plan ofthe work are, of course, original, and so are most ofthe data included in the notes on the various tests.Utility and conciseness have been the ends sought,and it is believed that no superfluous details havebeen included and that nothing essential has beenomitted.

Secondarily, the book was written to satisfythe needs of miners and prospectors, whose firstquestion on finding a new mineral is, "What doesit contain?" It is so elementary in its nature andthe directions are so complete that anyone witha common-school education, the proper instruments,and this book should be able in most cases to answerthis question for himself. It was for this class ofreaders alone that Chapters V and VI were included.Finally, it is believed that assayers and chemistswill find the book useful in making preliminaryexaminations of unknown substances.


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TABLE OF CONTENTS

CHAPTER IPAGE

BLOWPIPE INSTRUMENTS, REAGENTS AND OPERATIONS iCHAPTER II

METHODS OF TESTING FOR THE VARIOUS ELEMENTS WITHTHE BLOWPIPE

gCHAPTER III

OUTLINE FOR QUALITATIVE BLOWPIPE ANALYSIS 42CHAPTER IV

INDEX TO ALL OF THE TESTS YIELDED BY THE VARIOUSELEMENTS 47

CHAPTER VTHE DETERMINATION OF MINERALS BY MEANS OF THE

BLOWPIPE 50CHAPTER VI

THE ELEMENTARY PRINCIPLES OF CHEMISTRY 62TABLE OF ELEMENTS WITH THEIR SYMBOLS AND ATOMICWEIGHTS 73INDEX..


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BLOWPIPE ANALYSIS

CHAPTER IBLOWPIPE INSTRUMENTS, REAGENTS, ANDOPERATIONSNEARLY all dealers in assayers' or chemists' sup-

plies carry sets and separate pieces of blowpipeapparatus, and many pieces may be obtainedelsewhere, as will be seen from the following briefdescription of the articles used in the operationslater described. Most of the sets now on the marketare either too elaborate, too bulky, or else areimpractical, and great care should be exercisedin their selection.

Blowpipe. Many types are manufactured, andeach may have its own peculiar advantages, butalmost any one in which the aperture is nottoo large or too small will answer the purpose.The most satisfactory type has a trumpet-shapedmouthpiece, a small chamber in which the salivamay accumulate, and a removable tip. In portablesets it is not practicable to provide a blowpipewith a trumpet-shaped mouthpiece, however, and


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2 BLOWPIPE ANALYSISthis may be dispensed with, although somewhateasier on the lip muscles. Some makes are pro-vided with platinum tips, but this is an unnecessaryrefinement unless a great deal of work is to be done.A piece of very fine platinum or steel wire isthe best implement with which to clean out aclogged tip.Lamps. It is desirable, although not absolutelyessential, to have two lamps, one for oil and theother for alcohol. The latter is handier than theoil lamp for a few operations which will be men-tioned later, but in every case it can be replacedby the oil lamp without material disadvantage.The oil lamp should have a rectangular wickopening about half an inch long and less than halfas wide; the wick opening in the alcohol lampmay be of any shape. Care should be taken (par-ticularly with the oil lamp) not to have the wickso tight as to impede the flow of oil, to trim offcharred wick or irregularities as fast as they form,and to keep the wick just high enough not to smoke.The best fuel for the oil lamp is a mixture com-posed of two parts of lard oil and one part of kero-sene. This solidifies in very cold weather, butthaws out soon after lighting the lamp.Any other flame, such as that from a candle

or kerosene lamp, may be used instead of theselamps, and it is often necessary to resort to thesein the field, but the lamps and oil described will


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INSTRUMENTS, REAGENTS, OPERATIONS 3give the best results in the laboratory. In someplaces gas blowpipes are used, but one who hasattained proficiency with such apparatus is lost inthe field, so simpler instruments are preferable,

Platinum-tipped Forceps. The most convenienttype of these has tips of platinum on one end and ofbase metal on the other, the platinum-tipped endbeing provided with a spring which holds the tipstogether. Precautions as to the use of these forcepsare given later. They soon become discoloredwith use, but, if the precautions just mentionedare observed, this will not harm them. They maybe cleaned by using very fine sandpaper or scrapingwith a knife-blade.

Platinum Wire and Holder. The wire shouldbe of about 26 American or B. & S. Wire Gaugein thickness, and should be cut into pieces betweentwo and three inches long. The holder may be aglass tube into which one end of the wire is fused,but a mechanical holder with a hollow handle inwhich extra wires may be kept is more convenient.Precautions concerning the use of the platinumwire are given later.

Charcoal Supports. These should be made fromsoft wood and should be at least three incheslong, preferably more. They should not fissure,break, smoke, or ignite readily in the flame, andshould leave little ash when burned.

Unless liquid reagents have been used on the


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4 BLOWPIPE ANALYSIScharcoal in tests resulting successfully, the charcoalmay be used many times by scraping off the surfaceand the deposits formed thereon. Where liquidshave been used in successful tests, they are apt tosink for a considerable distance into the charcoal,and to cause a duplication of the test even aftera considerable depth of the charcoal has beenremoved.

Closed Tubes. These are usually formed ofthree-eighths inch glass tubing three or four incheslong, an inch of one end being bent to one sideand closed by fusion. Equally satisfactory resultsare secured from an implement formed by fusingtogether one end of an open tube (see below).Closed tubes cannot well be cleaned and shouldbe discarded after use. A strip of asbestos, or evenpaper, wrapped around the upper part of the tubemakes a convenient holder for hot tubes.Open Tubes. These are pieces of three-eighths

inch glass tubing three to five inches long. Theyshould be discarded after use unless the results havebeen negative, when the other end may be used for anew test. The asbestos or paper holder mentionedabove should be used for hot tubes.

Miscellaneous. A small slab of hard steel withat least one polished surface for use as an anvil.A small steel hammer with a flat face.A small horseshoe or bar magnet. The latter

may be procured with one end so shaped as to


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INSTRUMENTS, REAGENTS, OPERATIONS 5form a charcoal borer, but this is not neces-sary.Test-tubes.A hand-lens.A small piece of dark blue glass.

Reagent Bottles and Reagents. Wide-mouth, glass-stoppered bottles are the best in which to keep thedry reagents, which should include powdered (pref-erably dehydrated) borax, sodium carbonate, sodiumammonium phosphate (salt of phosphorus), acidpotassium sulphate, and bismuth flux (equal pro-portions of potassium iodide and sulphur).The wet reagents should be kept in glass bottleswith glass stoppers, and a dropper stopper willbe found a great convenience, although a satis-factory dropper can be easily made from a smallglass tube. The following reagents are needed:Hydrochloric (muriatic) acid. The concentratedacid should be diluted with an equal volume ofwater for most purposes.

Nitric acid. The concentrated acid is usuallyemployed.

Sulphuric acid (oil of vitriol). For most purposesthe concentrated acid should be diluted with fourvolumes of water. A great deal of heat is generatedwhen water and sulphuric acid are mixed, and thisshould be done with care. The acid should beadded gradually to the water, stirring constantly.Water should never be added to sulphuric acid.


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6 BLOWPIPE ANALYSISCobalt nitrate. The dry salt should be dissolved

in ten parts of water for use.,All acids should be handled with care, as theyare more or less corrosive and are capable of inflict-ing painful injuries when spilled on the skin.When this happens, or if they fall upon fabrics,their effects may be neutralized by moistening withammonia and then washing thoroughly with water.

Blowpipe Operations. The blowpipe is used forthe purpose of concentrating the flame into a long,slender cone which can be readily directed againstthe substance to be heated. It is very importantthat the blast be continuous and uniform, althoughthis may seem very difficult at first. The blast isnot produced by the lungs, but results from a bel-lows-like action of the distended cheeks. Duringthe operation, air is inhaled only through the nose,and is exhaled largely through the mouth and theblowpipe. Before trying to use that instrument,distend the cheeks, and, keeping the mouth closed,breathe through the nose for a moment; then openthe lips just enough to allow a little air to escapeslowly, and admit air from the lungs by a kind ofgulping action just fast enough to keep the cheeksfully distended. This may take some practice,but, when it is possible to allow air to escape con-tinuously from the mouth in this way no matterwhether it is being exhaled or inhaled through thenostrils, it is time to begin to use the blowpipe.


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INSTRUMENTS, REAGENTS, OPERATIONS 7Producing the Oxidizing Flame. Place the oil

lamp so that the longer dimension of the wick isfrom right to left, and set its right-hand edge upona pencil or some other low support so that it willtip somewhat to the left. Insert the tip of the blow-pipe about one-eighth of an inch within and justabove the right-hand side of the wick, and blowsteadily parallel to the wick, directing the flameto the left, and producing a clear blue flame aboutan inch long. If all of the flame cannot be thusdiverted to the left, or if there are yellow streaksin the flame, trim or lower the wick. If the wholeflame is inclined to be yellow, move the tip of theblowpipe a trifle to the left. If it is impossible toproduce a flame approaching the length mentionedabove, the opening in the end of the blowpipe istoo small, and this opening is too large when avery long, hissing flame is produced. In order tosucceed in blowing a steady flame, the hand mustrest upon some support, or the third and fourthfingers may be placed against the lamp.

In analytical operations it is sometimes desirableto oxidize substances to be tested, and at othertimes the aim is to reduce them to the metalliccondition; either result can be more or less readilyobtained with the blowpipe.A flame produced in the manner above describedis called an oxidizing flame, but the action of all

portions of such a flame is not oxidizing. The blue


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8 BLOWPIPE ANALYSIScone contains considerable carbon monoxide andis feebly reducing in its action, but just outside of theblue cone at the tip of the flame is an extremelyhot but nearly colorless zone which is stronglyoxidizing because of the free oxygen there present,and anything held in this zone about a quarter ofan inch from the tip of the blue flame will be in themost favorable position for oxidation.The oxidizing flame is hotter than the reducing,and the hottest part of this flame is just outside ofthe blue cone. In the absence of other instructions,substances should always be heated there.Producing the Reducing Flame. Hold the tip ofthe blowpipe about one-sixteenth of an inch aboveand to the right of the wick, and a long, yellowflame containing much unconsumed carbon willbe produced. This is sometimes called the smokyreducing flame. Where greater heat is required,the inner cone* of the oxidizing flame should be used.The strongest reducing action will take place at thetip of, and within, the yellow cone of the reducingflame. '

Other Operations. These will be described indetail when the various tests are discussed.


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CHAPTER IIMETHODS OF TESTING FOR THE VARIOUSELEMENTS WITH THE BLOWPIPETHE methods of testing for the various elements

with the blowpipe comprise blowpipe analysis,and many tests are included under this term, includ-ing a few in which the blowpipe is not required.The most useful are included in the following list,and will be discussed in the order named:

I. Treatment on charcoal without flux.II. Treatment on charcoal with flux.

III. Tests in closed tubes.IV. Tests in open tubes.V. Tests with borax beads.

VI. Tests with salt of phosphorus beads.VII. Flame tests.VIII. Cobalt nitrate coloration tests.IX. Tests with acids.The tests given should make it possible to recog-

nize the following elements and substances in mostof their combinations:Aluminum (Al), antimony (Sb), arsenic (As),

barium (Ba), bismuth (Bi), boron (B), cadmium(Cd), calcium (Ca), chromium (Cr), cobalt (Co),

9


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10 BLOWPIPE ANALYSIScopper (Cu), flourine (F), gold (Au), iron (Fe), lead(Pb), lithium (Li), magnesium (Mg), manganese(Mn), mercury (Hg), molybdenum (Mo), nickel(Ni), phosphorus (P), potassium (K), selenium (Se),silver (Ag), sodium (Na), strontium (Sr), sulphur(S), tellurium (Te), tin (Sn), titanium (Ti), tung-sten (W), uranium (U), vanadium (V), zinc (Zn),and water, silicates, and carbonates.

i. TREATMENT ON CHARCOAL WITHOUT FLUXA piece, the size of a BB shot or smaller, of thesubstance to be tested is pressed into the face of the

charcoal about half an inch from one end, or itmay be placed in a tiny cavity formed at that point,the object of embedding it somewhat in the charcoalbeing merely to prevent the particle from slidingoff or being blown away. The charcoal is thenheld in the left hand, pointing right and left, andthe blowpipe flame is blown upon the particle,which should be at the right end, in such a mannerthat the flame is not parallel with the charcoal butimpinges downward upon the particle at a smallangle.The piece tested is known as the assay.Heat the assay strongly for a minute or more in

the oxidizing flame, noting any odor or coloredflame that may be given off, and then examine thecharcoal for any coatings, known as sublimates, that


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METHODS OF TESTING 11may have been deposited thereon. If no verypositive results are thus obtained, repeat the opera-tion, using the reducing flame.

Care must be taken not to place the assay in deepholes that have been burned or scraped into thecharcoal. If this is done, the volatilized materialwill shoot up into the air, and no sublimate willdeposit on the charcoal.Most charcoal forms a little white ash when

burned; this should not be confused with a sub-limate.

Decrepitation (flying to pieces) of the assay maysometimes be prevented by heating it very slowly,i.e., holding it three or four inches from the flameat first and gradually bringing it nearer. Anothermethod, often satisfactory, consists of blowingthe flame against the upper part of the end of thestick of charcoal until it is red hot, thus graduallywarming the assay.

If the substance still decrepitates or if no resultsare obtained by the above methods of treatment,powder the material to be tested very fine and pressa small amount of the powder onto one end of thecharcoal, using a knife blade or spatula for thispurpose and forming a flat cake of the powder.Then proceed as before. If the material stilldecrepitates, moisten it with water and heat veryslowly.

Since chlorides of lead, copper, and other sub-


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12 BLOWPIPE ANALYSISstances yield white sublimates on charcoal that maybe confused with those mentioned below, it isessential that the charcoal tests be made beforeany hydrochloric acid has been put on the substanceto be tested.Not only is it necessary to note the color of

any sublimates produced, but their volatilityshould also be tested, as some are very volatile(can be burned off by applying the blowpipeflame for a fraction of a second) while othersare quite non-volatile (require the applicationof considerable heat to entirely remove them) inthe oxidizing flame, which should be used for thistest.The results obtained by any of the above means

may be thus interpreted:a. White, very volatile, light sublimate, depos-ited some distance from the assay. Strong

odor of garlic Asb. White sublimate with a blue border deposited

close to the assay, heavier and less volatilethan that yielded by As. Assay will oftencontinue to give forth white fumes afterheating has ceased Sb

c. White, fairly easily volatilized, heavy sub-limate near the assay, shading into alighter, more volatile coating further out.Odor of garlic Sb with As


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METHODS OF TESTING 13d. White and yellowish, crystalline (particles

are coarse and sharp-edged) sublimatewhich is changed to a deep ultramarine blueif touched for a, fraction of a second with thereducing flame. A copper-red coating mayform close to the assay Mo

(Prolonged heating with the oxidizing flameis required to obtain the white sublimate, which isyielded satisfactorily only by the sulphide molyb-denite.)

e. White when cold, yellow when hot, light,non-volatile sublimate, which, if moistenedwith cobalt nitrate and heated, will becomebright green when cold Zn

(This test should be conducted as follows: Pul-verize the material very fine and heat strongly andfor some time with the reducing flame; moistenthe charcoal where the sublimate has formed, orshould form, with a little cobalt nitrate; reheat theassay strongly with the reducing flame, and, if Zn bepresent in any form but the silicate, enough heatwill reach the spot moistened to turn it bright greenwhen cold.)

/. White, heavy sublimate with a blue outerborder close to the assay, a yellowish graycoating far from the assay, and a blackband between the two. All are easily vola-tile, burning off with a light bluish greenflame, which is also yielded by the assay Te

g. WThite when cold, yellowish when hot, light,


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14 BLOWPIPE ANALYSISnon-volatile sublimate, which, if moistenedwith cobalt nitrate and heated, will becomea dull bluish green when cold Sn

(This test should be conducted exactly like theone for Zn, described above.)

h. Yellow, volatile sublimate, inclining towardorange when hot, with a very volatile outerfringe of white. Yellow fumes and odorof garlic As with S

(This result is obtained when a sulphide of As isheated and volatilized too rapidly to permit of com-plete oxidation. Some of the material is volatilizedand deposited as the yellow sulphide of As.)

i. Yellow or orange, non-volatile sublimate,often with a bluish white outer border,deposited very close to the assay Pb

j. Yellow or orange, non-volatile sublimate,often with a bluish white outer fringe,deposited very close to the assay Bi

(Bi is much rarer than Pb, and the test describedabove may in the majority of cases be interpretedas indicating

Pb. Todistinguish

withcertaintybetween these two elements, mix the powdered sub-

stance with three or four times its volume of "bis-muth flux" (equal proportions of potassium iodideand sulphur), and heat on charcoal as usual. Thesublimate produced by Bi will be yellow near theassay, but bordered on the outer edge by a brilliantred, which will be missing in the case of Pb.)

k. Brown, volatile sublimate close to the assay,


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METHODS OF TESTING 15bordered by a very volatile, heavy whitesublimate. Odor of garlic As

(This result is obtained when the material isheated and volatilized too rapidly to admit of com-plete oxidation of the As. The brown sublimateis metallic As.)

/. Brown, fairly volatile sublimate close to theassay Cd

m. Reddish brown outer border on a black orsteel-gray volatile sublimate. A curiousand indescribable, but characteristic, odorand a blue flame Se

n. Lilac or lilac-red, volatile sublimate. .Ag with Pb(Ores yielding this result are rare.)

o. Blue flame and a suffocating pungent odor . . S(Se, Te, Cu chloride, and other substances burn

with a blue flame, but the blue flame combined withthe odor is distinctive of S.)

p. Magnetic residue left on charcoal. ..Fe, Ni, or Co(If the assay is infusible does not melt a mag-

netic residue indicates Fe.)

II. TREATMENT ON CHARCOAL WITH FLUXThis test is used when it is desired to reduce a

salt to the metallic condition, so the reduction flameis employed.The substance to be tested is finely pulverizedand mixed thoroughly with about three times as


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16 BLOWPIPE ANALYSISmuch powdered sodium carbonate and a littlepowdered borax. The mixture is then pressed intoa cake at one end of the charcoal and thoroughlyfused, beginning at the edges and working towardthe center. A little powdered charcoal thoroughlymixed with the material to be fused will oftenfacilitate the reduction. If the assay will not fusedown to a liquid mass, either the amount of flux(sodium carbonate and borax) or of heat applied isdeficient. In the latter case, raise the lamp wickand trim off the coal that forms upon it. It isalmost useless to hope for satisfactory results untila continuous blast can be blown. Sometimes afusion that appears to have come to a standstillmay be successfully completed by allowing theassay to cool, removing the little cake of semi-fusedmaterial with the point of a knife, turning it upsidedown on the charcoal, and proceeding as at first.Some charcoal usually adheres to the upper surfaceof the cake and this has a strong reducinginfluence. This process is always necessary in thecase of Sn.

Metallic Sb and many sulphides and arsenidesyield metallic globules by this test, but these aredistinguishable by their brittleness from thosedescribed below.

In addition to sublimates identical with those thatform on charcoal without flux, other results areproduced which may be thus interpreted:


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METHODS OF TESTING 17a. White when cold, yellow when hot, light,

non-volatile sublimate, which, if moistenedwith cobalt nitrate and heated, will becomebright green when cold Zn

(Zn compounds which give this test with diffi-culty or not at all when treated without flux willgive a good color when flux is used. The operationshould be conducted as described under I.e. Careshould be exercised not to confuse the green Zncoloration that appears in front of the assay witha blue color on the assay itself. The latter willappear whenever fusible material is moistenedwith cobalt nitrate and heated, regardless of thepresence or absence of Zn.)

b. Lilac or lilac-red, moderately volatile subli-mate and a white, malleable, metallicbutton Ag with Pb

(Ores yielding this result are rare.)c. Yellow or orange, non-volatile sublimate,

often with a bluish white outer border,deposited very close to the assay, and a mal-leable, metallic button, grayish white on afreshly cut surface but oxidizing on expos-ure to the air Pb

d. Yellow or orange, non-volatile sublimate,often with a bluish white outer border,deposited very close to the assay, and arather brittle, metallic button, grayish whiteon a freshly cut surface but oxidizing onexposure to the air Bi

(The button may flatten somewhat when firsthammered but is not malleable like Pb. This will


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18 BLOWPIPE ANALYSISusually suffice to distinguish between the twometals, or the test with " bismuth flux," describedunder I.;., may be applied.)

e. White, malleable, metallic button Ag(To distinguish between Ag and Pb buttons,

place the button to be tested in a small depressionon a clean piece of charcoal and heat strongly inthe oxidizing flame. If Pb, the characteristicyellow sublimate will form, and, if Ag, there will beno coating or only a faint brownish one. Thetwo metals may also be distinguished after somepractice by the fact that the Ag is decidedly harder;the flattened button may be cut only with difficultywhile Pb cuts easily.)

/. White, malleable, metallic buttons of smallsize, which show little or no tendency tocoalesce into one large button. A whitewhen cold, yellowish when hot, light, non-volatile sublimate may also form Sn(To distinguish between Sn and Ag, rememberthat the latter forms one large button, usually, whilethe many small buttons of the former can beforced to coalesce only with great difficulty andafter prolonged blowing. Another method of dis-tinguishing

them is to alloy the button in doubtwith a somewhat smaller amount of Pb, by melt-ing the two together, and then to note whether thecharacteristic lilac Ag-Pb sublimate is producedin the oxidizing flame. A third method involvesan endeavor to secure the sublimate and cobaltnitrate color reaction of Sn as described under I.g.)

g. Yellow, malleable, metallic button Auh. Red, malleable, metallic mass, which it is


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METHODS OF TESTING 19impossible to fuse into a single button bymeans of the blowpipe Cu

i. Gray, malleable, magnetic particles (notglobules) Fe, Co, or Ni

(The three may be readily distinguished by the"bead tests" (V.),q.v.)j. The thoroughly fused mass forming the

assay, when placed on a clean, moistenedsilver surface, produces a dark brown or *black stain S, Te, or Se

(This test is very delicate, but it must be madecarefully in order to succeed. Exactly three partsby volume of sodium carbonate must be used forone part of the substance to be tested, and it is bestto press the fused mass with a knife or hammer-head against the silver surface which has previouslybeen moistened with a drop of water, and to holdit there for a minute or two. Sometimes a slightstain which may be rubbed off with the fingers orwashed off with water is produced. This shouldbe ignored, as the S, Te, or Se stain is permanent.

Unless Te or Se have been detected by testsI./, I.m., lll.c., III./., III./., III.0., IV.., orIV.&., the presence of a dark stain on the silvermay be assumed to indicate S.)

III. TESTS IN CLOSED TUBESIt is sometimes desirable to treat the substance

just as it is, while for other tests it is best to mixit with three or four times as much sodium carbonateor acid potassium sulphate. In any case, the wholecharge should be powdered as fine as possible and


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20 BLOWPIPE ANALYSISenough introduced within a tube to fill it to a heightof about half an inch. This may be done with asmall paper or tin funnel or chute, or even with avery small knife-blade.The lower portion of the tube and the chargecontained therein should then be heated to rednessfor some time and the results noted. An alcoholflame alone may be used for this purpose, but thework may be hastened and the results often improvedby using the blowpipe on the alcohol or oil flame.Care must be exercised not to use too high a heator the glass will melt, swell, and break open, orwill completely seal up the charge.

Possible results obtainable without flux are asfollows :a. Moisture in drops on the walls of the tube a

short distance above the charge H^Ob. Liquid, mirror-like sublimate that collects inglobules Hg

(Only the native metal will give this result with-out using sodium carbonate flux.)

c. Mirror-like sublimate of large and small,solid, white globules Te

d. Mirror-like sublimate of very small, solid,white globules Cd

(Cd and Te are easily distinguished by usingtests I./, and I.I.)

e. Mirror-like, solid, black sublimate, often withdull black sublimate above, both volatile As


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METHODS OF TESTING 21(A sulphide will not yield this result without

using sodium carbonate flux.)/. White sublimate composed of tiny globules

in a narrow zone immediately above thecharge, with a ring of yellow globules orliquid at the base, both very slowly vola-tile Te

(Tests III.c. and III./, are given by differentores of Te or are the result of the application of dif-ferent temperatures.)

g. White, faint, very slowly volatile sublimatewith a little yellow liquid close to thecharge . . Sb

(A sulphide will not yield this result withoutusing sodium carbonate flux.)

h. Reddish liquid when hot, yellow solid whencold ; may be almost white when cold if theamount is small S

i. Dark red liquid when hot, orange solid whencold As with S

j. Black when hot, reddish brown when cold,difficultly volatile sublimate Sb with S

k. Black, volatile sublimate. If the tube isbroken and the sublimate rubbed with acloth, it will sometimes turn red, but thisis unusual Hg with S

/. Black, difficultly volatile sublimate, composedof irregularly shaped drops, liquid when hot.Shades above into a volatile sublimate,


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22 BLOWPIPE ANALYSISreddish brown when hot and dark red whencold Se

Possible results obtainable with sodium carbonateflux are as follows:m. Moisture in drops on the walls of the tube

a short distance above the charge EkOn. Liquid, mirror-like sublimate that collects

in globules Hgo. Mirror-like sublimate of large and small,

solid, white globules Tep. Mirror-like sublimate composed of very small,

solid, white globules Cd(Cd and Te are easily distinguished by using

tests I./, and I./.)q. Mirror-like, solid, black sublimate, often

with a dull, solid, black, sublimate above,both volatile As

r. White, faint, very slowly volatile sublimatewith a little yellow liquid close to the

assaySb

Possible result obtainable with acid potassiumsulphate is as follows:s. After boiling the contents of the tube vigor-

ously for several minutes, the glass immedi-ately above the charge is etched or rough-ened F

(This result is most easily recognized by breaking


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METHODS OF TESTING 23the tube, washing the interior thoroughly, andthen scratching the portion that may be etchedwith the point of a knife. If etching has occurred,the surface will feel much rougher than doesunetched glass.)

IV. TESTS IN OPEN TUBESNo flux is used in these tests. The substance

to be treated is merely finely powdered, a little ofit is placed about half an inch from one end withina tube, and it is then heated strongly while the tubeis held as highly inclined as is possible withoutlosing the charge. The alcohol flame may be used,but as good or better results are produced by theoil flame and the blowpipe. In fact, the greaterheat of the blowpipe-concentrated oil flame isessential for some of the tests, and this shouldalways be used after securing negative results withthe alcohol flame.The tests are very delicate, but are ordinarily

used only to corroborate unsatisfactory charcoaltests.

Possible results may be thus interpreted:a. Moisture in drops on the walls of the tube. . H2Ob. Characteristic, suffocating, pungent odor ... S

(Many sulphides fail to yield this test.)c. White, light, very volatile, crystalline subli-

mate, and odor of garlic Asd. White, heavy sublimate, less volatile than


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24 BLOWPIPE ANALYSISthat given by As, and dense white fumes.Slender white crystals may form 'on thecharge if the heat is not too great Sb

e. White when cold and light yellow when hot,very heavy, almost non-volatile sublimateand very dense white fumes which passalong the under side of the tube. If a largeamount of material be heated very intensely,a little difficultly volatile sublimate, blackwhen hot and reddish brown when cold,may form Sb with S

/. White, faint, non-volatile sublimate close tocharge Pb with S

g. White, slowly volatile sublimate, which fusesto globules which are yellow hot and color-less cold. Often, yellow globules formaround, and a gray sublimate collects abovethe charge Te

h. White, non-volatile sublimate, fusible toyellow drops, lighter when cool Bi with S

(Bi with S and Te are readily distinguished bytests I./, and I.y., the latter being characteristic ofBi no matter in what combinations it may be.)i. White, delicate crystals, yellow when hot,

form near and over the charge after pro-longed heating Mo

(This result is yielded only by the sulphide.)j. Yellow, volatile sublimate, inclining toward

orange or red when hot, with a very volatile


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METHODS OF TESTING 25outer border of white. Yellow fumes andodor of garlic As with S

(This result is often produced when a substancecontaining S and As is heated too rapidly to allowof complete oxidation.)

k. Black, volatile sublimate where very heavy,which shades toward the upper end of thetube into a volatile coating that is reddishbrown when hot and dark red when cold.A curious and indescribable but character-istic odor and lilac fumes, best seen againsta black background Se

/. Black, very volatile sublimate with brownishor iridescent bands and sometimes a mirror-like deposit close to the charge. Whitefumes, a white volatile sublimate beyondthe black, and characteristic odor of garlic. As

(This result is produced when a large amountof material is heated too rapidly to allow of completeoxidation.)

V. TESTS WITH BORAX BEADSThe beads are made by heating the end of a

platinum wire to redness, dipping it into somepowdered or granulated borax, reheating the wireand adhering borax, and continuing the processuntil the bead when thoroughly fused is as largeas will remain on the wire. If too small, the coloris hard to see, and a bead that is too large will keep


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26 BLOWPIPE ANALYSISfalling from the wire. Some of the oxidizing flametests may be made with the alcohol flame, but allmay be secured more quickly and easily with theoil flame and the blowpipe.The bead should always be kept at the end ofthe wire, and this may be done by bending the endof the wire and holding it in such a manner that theblowpipe flame is always directed against the sideof the bead furthest from the end, forcing it to theend. A loop to hold the bead should not be formedin the wire; it is unnecessary if the wire is clean, anduses up the platinum very rapidly.Before making any bead test, the material to betested should be powdered and thoroughly roastedon charcoal. This is accomplished by spreadingthe powder on the surface of the charcoal in a flatcake, so as to allow free access of air, and heatingto a dull red in that part of a small oxidizing flamethat is well outside of the blue cone. The reducingflame should then be applied, and, finally, theoxidizing flame used until no odors of As or S areapparent and the assay ceases to burn with a coloredflame or to volatilize. Fusion should be preventedif possible. This may be accomplished by mixingthe fusible substance with about an equal volumeof powdered charcoal, which keeps the particlesseparated and soon burns away. No satisfactorybead tests need be expected from a substance whichvolatilizes completely without solidification.


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METHODS OF TESTING 27To make the tests, heat the bead as hot as possible

and touch it to a very little (a few grains) of thepowdered substance to be tested. Some of thelatter will adhere to the bead, which should thenbe heated in the oxidizing flame and any resultingchange of color noted. This process should thenbe repeated on the same bead, using the reducingflame. If the results are negative or too faint to bedecisive, more of the powder should be dissolvedin the bead and the process continued until a rela-tively large amount has been added, when the beadis said to be saturated.The colors of the beads are due to the presenceof oxides of the various elements, and these oxidesvary greatly in their coloring powers. In somecases, deep, vivid colors are obtained from a fewgrains of the powdered substance, while in otherinstances it is necessary to dip the bead many timesinto the powdered substance before the character-istic colors are produced. Beads in the former classmay be considered saturated when the color is sodeep as to make them practically opaque; thosein the latter class are saturated when they refuseto absorb more of the material. This may requirehalf a dozen applications of the powder.

In case a bead becomes so saturated upon thefirst application to the powder that its color isindeterminate, it may be flattened upon the anvilwhile still warm and the color readily observed in


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28 BLOWPIPE ANALYSISthe thin cake thus formed. This cake may thenbe broken into many pieces, and a few of theseadded to a fresh bead without saturating the latter.All beads, even when saturated, should be perfectlyclear unless otherwise noted. If this is not thecase, a higher heat should be applied or new beadsformed, as a bead that has been worked with forsome time in different flames is apt to becometranslucent or opaque.

It should be remembered that a bead containingincompletely roasted powder is very apt to be brownin both flames, and then prolonged heating isrequired to expel the S or other interfering elementor elements.The bead test should never be used on a substance

suspected to contain Cu, as that element will alloywith the platinum and give Cu beads wheneverthe same wire is used in subsequent tests. Otherelements are apt to alloy with the platinum, par-ticularly during the formation of reduction beads,and these will make the wire brittle and cause it tobreak easily, but will not interfere with tests madebefore the break occurs.To remove a bead from the wire, either break

it off on the anvil or jar it off while in a molten con-dition. When the latter method is used, it is agood idea to save the beads obtained from knownsubstances and compare them with those given byunknown materials.


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METHODS OF TESTING 29The most difficult operation involved in making

the bead tests is the production of a good, con-tinuous reducing flame, yet this is very im-portant and must be mastered. Manganese givesa very highly colored bead in the oxidizing flame,and the production of the colorless bead in thereducing flame is a good test of ability in this line.

If a substance contains two elements each ofwhich yields a characteristic bead, one may somodify the other as to give intermediate results.However, in most cases of this kind, one color willcompletely mask the other, and this makes it thenimpossible to detect both elements.The accompanying table indicates the colors ofthe borax and salt of phosphorus beads (see below)yielded by the elements named in both oxidizingand reducing flames. The following abbreviationsare used: O.F. = oxidizing flame. R.F. = reducingflame. W=warm bead. W*= saturated warmbead. C =cold bead. C*= saturated cold bead.As an illustration, consider iron. The table

shows that iron gives in the oxidizing flame a boraxbead that is yellow while warm and colorless whencold unless the bead is saturated; then, it is yellowwhen cold. In the reducing flame, the bead isgreen when warm and colorless when cold unlesssaturated, when it is bottle-green when cold. Like-wise, both the non-saturated and saturated saltof phosphorus beads are yellow when warm and


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30 BLOWPIPE ANALYSIS


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METHODS OF TESTING 30a

NOTES ON TABLE OF BORAX BEAD TESTSNOTE i. The strongly saturated bead is a dull bottle-

or olive-green when cold after treatment with the reduc-ing flame. A very small quantity of ore should be usedfor the unsaturated bead tests.NOTE 2. The strongly saturated bead is opaque after

treatment with the reducing flame.NOTE 3. Saturated and non-saturated warm beads are

greenish yellow after treatment in the oxidizing flame.

NOTE 4. The cold, non-saturated bead is yellowishgreen after treatment with the oxidizing flame. A smallquantity of ore should be used for the unsaturated beadtests.

NOTE 5. The strongly saturated bead may be opaqueand dark brownish red after treatment in the reducingflame. A very small quantity of ore should be used forthe unsaturated bead tests.NOTE 6. A very small quantity of ore should be used

for the unsaturated bead tests.NOTE 7. An extremely small quantity of ore should

be used for the unsaturated bead tests.NOTE 8. The saturated bead is gray and opaque after

treatment with the reducing flame.


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306 BLOWPIPE ANALYSIS

NOTES ON TABLE OF SALT OF PHOSPHORUSBEAD TESTS

NOTE i. The warm bead is pale to deep yellowish green(depending upon the degree of saturation) after treatmentwith the reducing flame. A very small quantity of oreshould be used for the unsaturated bead tests.NOTE 2. The cold saturated bead is very pale violet

after treatment with the reducing flame.NOTE 3. The cold saturated bead is greenish blue after

treatment with the reducing flame.NOTE 4. The green bead obtainable with the reducing

flame cannot be reoxidized to yellow.NOTE 5. A small quantity of ore should be used for the

unsaturated bead tests.NOTE 6. The cold non-saturated bead is pale green after

treatment with the reducing flame.NOTE 7. The strongly saturated bead may be opaque

and dark brownish red after treatment in the reducingflame. A very small quantity of ore should be used forthe unsaturated bead tests.NOTE 8. A very small quantity of ore should be used

for the unsaturated bead tests.NOTE 9. An extremely small quantity of ore should be

used for the unsaturated bead tests.


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METHODS OF TESTING 31


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32 BLOWPIPE ANALYSIScolorless when cold in the oxidizing flame, while inthe reducing flame the non-saturated salt of phos-phorous bead is pale yellowish green when warmand colorless when cold, and the saturated beadis deep yellowish green when warm and brownwhen cold.

VI. TESTS WITH SALT OF PHOSPHORUS (SODIUMAMMONIUM PHOSPHATE OR MICROCOSMIC SALT)BEADSThese tests are made in exactly the same manner

as are those with borax beads and the same pre-cautions should be observed. The salt of phosphorusis, however, much more liquid than borax, especiallywhen first heated, and drops off the wire veryeasily. It will be found necessary to buildthe bead up gradually by the addition of smallparticles picked up on the hot wire one after theother and to use smaller beads than with borax.If difficulty in retaining the bead is still ex-perienced, it will be found advisable to form aloop in the end of the wire by bending it aroundthe point of a lead pencil. In any case, it is bestwhile forming the bead to allow the flame toplay upon the under side of the fusing mass, thusbuoying it upward and decreasing its tendency todrop off.The salt of phosphorus tests are necessary for


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METHODS OF TESTING 33the recognition of some of the elements, but in mostcases they will be found useful merely to corroborateunsatisfactory borax bead tests, and they may oftenbe omitted.The accompanying table indicates the colors of

both salt of phosphorus and borax beads in bothoxidizing and reducing flames. The abbreviationsand use of the table have been explained in thediscussion of the tests with borax beads.

VII. FLAME TESTSWhen volatilized, certain substances impart moreor less decided colors to a flame, and the recognition

of these colors constitutes distinctive tests for suchelements.The flames are best seen in a dark room or against

a dark background, and even then it requires closeapplication to perceive the very brief flashes of colorwhich constitute the tests in many instances.Four different methods of making these tests may

be used, and they should be applied in the ordergiven, it being unnecessary, however, to seek furtherresults after a determination has been made by anyof the methods. If two elements, both of whichyield characteristic flames, are present, one willusually so mask the other as to make the recognitionof both impossible.The second, third, or fourth method shouldnever be used upon a substance with a metallic


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34 BLOWPIPE ANALYSISlustre without a thorough preliminary roasting,as As, Sbj Pb, and other easily reduced elements,are apt to form fusible alloys with the platinum wireor forceps and thus ruin them.Some elements yield their characteristic flamecolors best at a low heat while others require'the highest heat available, so it is always bestto use both low and high temperatures for eachtest.Some substances which ordinarily yield no flame

tests may have some of their constituents convertedinto volatile, flame-tinting compounds by treatmentwith some reagent, usually HC1 or EkSO^ In fact,it is a safe practice always to dampen the materialto be tested with HC1, not even trying a test withoutthe use of that acid. If no tinted flame results,H2SO4 should be tried.

First Method. Place a fragment or some ofthe powdered substance upon charcoal, moistenwith a few drops of concentrated HC1, and heatin the hottest portion of the blowpipe flame. Theonly result that need be sought and noted (theothers being more easily obtained, or the elementsbeing more easily recognized, by other methods) isthe following:a, Azure-blue flame, with or without flashes,

or a border, of emerald green Cu(If this test results favorably, care should be taken

not to make the bead tests, which could only


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METHODS OF TESTING 35yield Cu, or to heat the material in the platinumforceps, since in either of these operations theCu will alloy with the Pt and ruin it.)

Second Method. (This is applicable only to car-bonates. See IX.&.) Seize a sliver of considerablesize in the. platinum forceps, moisten it with diluteHC1 (one part of acid to three or four parts of water),and hold the particle near the base of the flame of analcohol lamp, the blowpipe flame not being used forthis test. Ifthe result is negative, repeat the operatipn,but use the hot tip of the alcohol flame instead ofthe base. In a few cases, cold or hot concentratedacid is. required and these should be tried as a lastresort, but the dilute acid should be first tried, asthere are several substances which will not give agood reaction with the strong acid.The splinter should be moistened by immersingit in the acid and holding it there until there is a

vigorous effervescence (evolution of gas). Pure,fresh alcohol and acids should be used for thesetests, as otherwise a yellow Na flame is apt to bevery prominent and may mask .the flames yieldedby Ba or Pb.

If an alcohol lamp is not available, all of the testsdescribed below may be obtained by using themethod next given, but the results are more vividand are easier obtained in the manner just described,if the substance tested is a carbonate.

Possible results may be thus interpreted:


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36 BLOWPIPE ANALYSISb. Scarlet flame, lilac through blue glass Sr

(A Li flame might easily be confused with thatfrom Sr, but no known Li carbonate occurs innature, so this test when obtained in the abovedescribed manner always indicates the presenceof Sr.)

c. Yellowish red flame, greenish through blueglass Ca

(This is difficult to distinguish at first from theSr flame, but is considerably less vivid and isinclined toward orange. It may be positively identi-fied by the fact that Ca salts give good tests nomatter whether dipped in concentrated or diluteacid and dilute acid must be used to secure a goodSr flame.)

d. Yellow flame Na(This test is too delicate to be used with safety

unless very intense and persistent. Specimensthat have been handled will become sufficientlycharged with Na from the fingers to give a goodflame test.)

e. Yellowish green flame, pale tint Ba(Masked by strong Na flame.)

/. Blue flame, pale tint Pb(Hot, concentrated acid is required for this test,and even then the color will appear for only an

instant when the splinter is held in the tip of theflame.)

Note. A vivid Cu flame may be obtained in thismanner, but this should never be attempted, as theforceps will thereby be ruined.

Third Method. Hold an extremely fine splinter


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METHODS OF TESTING 37(as slender as a very fine needle) in the platinumforceps, moisten it with a drop of HC1, and introduceit into the hottest part of the blowpipe flame. Aflash or a continuous appearance of color may beimparted to the flame. If the result is negativeor unsatisfactory, remoisten the splinter and reheat.If this fails, repeat the operation with H2$O4 insteadof HC1. Should the splinter decrepitate, try heatingit very slowly, and,, if it still flies to pieces, the fourthmethod must be used.

Possible results may be thus interpreted:g. Carmine flame, violet through blue glass Lih. Scarlet flame, lilac through blue glass Sr

(The colors of the Li and Sr flames are so similarthat they are easily confused, but they may bereadily distinguished by the fact that a substancethat has been ignited and has given a Sr flame willturn moist red litmus paper blue when crushedand placed upon it. Li minerals show no effectof this kind.)

i. Yellowish red flame, greenish through blueglass Ca

(This is difficult to distinguish at first from theSr or Li flames, but is considerably less vivid thaneither and is inclined toward orange.)

j. Yellow flame Na(This test is too delicate to be used with safety

unless very intense and persistent. Specimensthat have been handled will become sufficientlycharged with Na from the fingers to give a goodflame test.)


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38 BLOWPIPE ANALYSISk. Yellowish green flame, pale tint Ba

(Masked by strong Na flame.)/. Bluish green flame, pale tint P

(H2SO 4 must be used for this test and the result.is not usually very satisfactory.)

m. Bright green flame B(B minerals which do not give a flame test in

this way should be powdered and mixed thoroughlywith about three volumes of a mixture of equalparts of powdered acid potassium sulphate andcalcium fluoride fluorite. This should be intro-duced into the flame as described in the fourthmethod.)

n. Blue flame, pale tint Pbo. Blue flame, pale tint Sb

(The reducing flame must be used to obtainthis result, which is neither very satisfactory nordeterminative. Care should be taken not to testan Sb ore in this way, as it is apt to alloy with, andruin, the platinum forceps.)

p. Violet flame, violet through blue glass K(This is difficult to obtain in most cases and

is entirely masked by a pale Na flame. The latteris, however, entirely absorbed by blue glass, whichtransmits the K flame as of lilac or violet color,depending upon the shade of the glass.)

Note. A vivid Cu flame may be obtained in thismanner, but this should never be attempted, as theforceps will thereby be ruined.

Fourth Method. Powder the material to betested very fine, pick up a little of this powder upon


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METHODS OF TESTING 39a flattened platinum wire moistened with HC1,and introduce the powder-coated wire into thehottest part of the blowpipe flame. Momentaryflashes or continuous appearances of color may beimparted to the flame, which are to be interpretedas under the third method. If the results are nega-tive, repeat the operation, using EfeSC^ instead ofHC1.This method is not usually very satisfactory and

should not be used unless it is impossible to obtaina splinter fine enough to be tested by the thirdmethod. Minerals which decrepitate badly, whichare very soft, or which occur as a powder must, ofcourse, be tested by this last method.

VIII. COBALT NITRATE COLORATION TESTSTo make these tests, hold a small splinter of the

substance to be tested in the platinum forceps andheat it in the blowpipe flame to the highest possibletemperature. Then examine it with a lens; if itshows any signs of fusion, this test cannot be applied.If non-fusible, moisten it with cobalt nitrate andignite strongly in the hottest part of the blowpipeflame. It will first turn black but after prolongedheating may assume a characteristic tint. If asplinter of the substance cannot be obtained, itshould be powdered and the test conducted upona flat cake of the powder upon charcoal. Longer


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40 BLOWPIPE ANALYSISheating is required by this method, however, andthe results are not apt to be as satisfactory.This test can be applied only to non-fusible,

white or faintly tinted minerals, or those whichbecome white or faintly tinted upon ignition.

Possible results may be thus interpreted:a. Blue coloration Al or Zn silicate

(Al minerals and Zn silicate give identical resultsby this test. If Zn has been obtained by tests I.e.,or II. a., it is impossible to test for Al in thisway. If Zn is not present, this test may be inter-preted as indicating the presence of Al. Occa-sionally

a little greenforms with the blue on Zn

silicates, which never happens in the case of Al min- .erals.)

b. Green coloration, dark Sbc. Green coloration, bright tint, best seen when

cold Znd. Pinkish or flesh-tint coloration Mg

IX. TESTS WITH ACIDSThese are really purely chemical and should notbe included under blowpipe analysis, but two

are so simple and useful that they are given below.a. The finely powdered material, when boiled

almost to dryness in concentrated nitricacid, yields a gelatinous mass a silicate

b. The powdered material effervesces vigorously


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METHODS OF TESTING 41when placed in a test-tube containing somecondition of hydrochloric acid a carbonate

(In some cases the tests appear in cold, diluteacid, while, in other instances, hot dilute, cold con-centrated, or hot concentrated may be required.It is best to experiment with the dilute acid first,and then, if results are negative, to increase thetemperature until all conditions of acid have beentried.

It is not always necessary to powder the materialto be tested, but this is sometimes required andnever does any harm.

Care should be taken not to confuse effervescence(escape of CC>2) with boiling (escape of steam)when boiling acid is used.Some sulphides may effervesce in hydrochloricacid, but these may be distinguished from carbon-ates by the fact that they yield a gas (E^S) thatsmells like bad eggs.)


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CHAPTER IIIOUTLINE FOR QUALITATIVE BLOWPIPEANALYSIS

BLOWPIPE analysis is ordinarily used for the pur-pose of ascertaining what elements an unknownsubstance contains, this process being known inchemistry as qualitative analysis. It is not possible,excepting in a few cases and by the application ofvery refined methods not here discussed, to deter-mine how much of an element is present to makea quantitative analysis of the substance; but, if theelements present are known, it is usually possibleto determine the nature of the substance by applyingthe principles set forth in Chapter V. Where thenature of a mineral has thus been determined, it iscomparatively easy to compute the percentage com-position with considerable accuracy in many cases,by applying the principles presented in ChapterVI, A tabulation of the principal elements presentin many common minerals are given in Chap-ter V. Even when the name and nature ofthe mineral cannot be ascertained by blowpipemethods, the ability to ascertain the commerciallyimportant elements that it contains is often of the

42


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QUALITATIVE BLOWPIPE ANALYSIS 43greatest value, since it is then possible to decidewhether it is worth while to procure a chemicalanalysis or an assay of the substance.The following scheme has been devised as a guidefor making a complete qualitative analysis of anunknown substance with the greatest economy oftime and labor. It should not be expected thatevery mineral containing As, for instance, will yieldevery test for As mentioned in Chapter II or in thefollowing outline, but in most cases the mineralwill give one or more of the tests there given. Itis poor practice to assume that a mineral containsa certain element and then test for that element,repeating the operation for other elements. A farbetter plan is to follow the outline rigidly and todraw conclusions from the results secured. Thissaves time and makes it impossible to forget to trytests.

If it is suspected that Hg is present in a substance,it should be tested only in the closed tube (seeIII.6.), as the vapois are very poisonous.

OUTLINEA. Powder material very fine and place upon char-

coal, pressing out with a knife-blade into aflat cake. Moisten with water if necessary tokeep the charge from flying off the charcoal,

i. Test for As, Sb, Sb with As, Mo, Te, As with


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44 BLOWPIPE ANALYSISS, Pb, Bi, Cd, Se, Ag with Pb, and S.(Seel.)

2. Test for Fe. (See I.p.)Separate the residue from the above tests

into two portions and save one of these for alater test. On the portion still remaining on thecharcoal make:

3. Test for Zn and Sn. (See I.e. and I.g.)4. Test for Cu on residue from A.3. (See VII.a.)5. Test for Al, Mg, Zn, Sb, and Zn silicate on

residue from A.4. (See VIII.)(This test can be made only upon light colored,

infusible material, and need not be tried if Zn hasalready been found.)

B. If A.4. gave no Cu flame (if Cu is present it isuseless to make the following tests) make boraxand salt of phosphorus bead tests for the ele-ments named below, using the residue savedfrom A. 2.

i. Test for Fe, Mo, Ti, W, U, V, Cr, Cu, Co,Mn, and Ni. (See V. and VI.)

C. In case A.I. gave a result that might be inter-preted as indicating either Pb or Bi, use thebismuth flux test to distinguish them,

i. Test for Bi on some of the original material,using bismuth flux. (See I./.)

D. If A.4. gave no Cu flame (if Cu is present it isuseless to make the following tests), hold apiece of the original material as large as a tooth-


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QUALITATIVE BLOWPIPE ANALYSIS 45pick or match in the platinum forceps andmake the flame tests as described under VII.,Second Method.

1. Test for Sr, Ca, Na,- Ba, and Pb carbonates.(See VII., Second Method.)

If no satisfactory results are obtained fromD.I., make the flame tests as described underVII., Third Method.

2. Test for Li, Sr, Ca, Na, Ba, P, B, Pb, Sb,and K. (See VII., Third Method.)

If no satisfactory results are obtained fromD.2., make the flame tests as described underVII., Fourth Method.

3. Test for Li, Sr, Ca, Na, Ba, P, B, Pb, Sb, andK. (See VII., Fourth Method.)

E. On some of the original material, powdered,make the closed tube tests without flux.1. Test for H2O, Hg, Te, Cd, As, Sb, S, As with

S, Sb with S, Hg with S, and Se. (See Ill.a.to/.)

On some of the original material, powdered,make the closed, tube tests with flux, providedE.I. has not yielded determinative results.

2. Test for H2O, Hg, Te, Cd, As, and Sb. (SeeIII.w. to r.)On some of the original material, powdered,make the closed tube test with acid potassium

sulphate.


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46 BLOWPIPE ANALYSIS3. Test for F. (See III.*.)

F. On some of the original material, powdered,make the open tube tests.i. Test for H2O, S, As, Sb, Sb with S, Pb with

S, Te, Bi with S, Mo, As with S, and Se.(See IV.)

Note. It is always well to make tests E. and F.even when A. has given determinative results, asseveral of the elements determined by means oftests E. and F. may fail to show in test A. It isa good practice to corroborate results obtained bytest A. by means of tests E and F.G. On some of the original material, powdered,

make the tests on charcoal with flux.1. Test for Zn, Ag with Pb, Pb, Bi, Ag, Sn, Au,Cu, and Fe, Co, or Ni. (See II.)On the residue from G.I., make the silvertest for S, Te, or Se, provided these elements,or one of them, have not already been detectedby other tests.

2. Test for S, Te, or Se. (See II.;.)H. On some of the original material, powdered,make the tests with acids in test-tubes.1. Test for a silicate with nitric acid. (See IX.a.)2. Test for a carbonate with hydrochloric acid.

(SeeIX.6.)


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CHAPTER IVINDEX TO ALL OF THE TESTS YIELDED BYTHE VARIOUS ELEMENTSIT is the purpose of this index to furnish a complete

list of all the blowpipe tests for any element dis-cussed in the preceding pages. It will be founduseful where the interest is concentrated upon one ortwo elements to the exclusion of all others, but shouldnot be used in making a complete qualitative blow-pipe analysis of a substance. It should not beexpected, that any mineral will necessarily yield allof the tests for each of the constituents.The references here given are to the page orpages on which tests for the various elements aredescribed.

Aluminum: 40.Antimony: 12, 21, 22, 24, 38, and 40.Arsenic: 12, 14, 15, 20, 21, 22, 23, 24, and 25.Barium: 36 and 38.Bismuth: 14, 17, and 24.Boron: 38. 47


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48 BLOWPIPE ANALYSISCadmium: 15 and 20.Calcium: 36 and 37.Chromium: 30 and 31.Cobalt: 15, 19, 30, and 31.Copper: 19, 30, 31, and 34.Fluorine: 22.Gold: 18.Iron: 15, 19, 30, and 31.Lead: 14, 15, 17, 24, 36, and 38.Lithium: 37.Magnesium: 40.Manganese: 30 and 31.Mercury: 20, 21, and 22.Molybdenum: 13, 24, 30, and 31.Nickel: 15, 19, 30, and 31.Phosphorus: 38.Potassium: 38.Selenium: 15, 19, 22, and 25.Silver: 15, 17, and 18.Sodium: 36 and 37.Strontium: 36 and 37.Sulphur: 14, 15, 19, 21, 23, 24, and 25=Tellurium: 13, 19, 20, 21, 22, and 24.Tin: 14 and 18.Titanium: 30 and 31.Tungsten: 30 and 31.Uranium: 30 and 31.


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TESTS YIELDED BY VARIOUS ELEMENTS 49Zinc: 13, 17, and 40.Water: 20, 22, and 23.A carbonate: 41.A silicate: 40.


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CHAPTER VTHE DETERMINATION OF MINERALS BYMEANS OF THE BLOWPIPE

WHILE the determination of the constituent ele-ments of a mineral is the usual aim of a blowpipeanalysis, it is often desirable to be able to assignthe correct mineralogical name to the substance,since, when this can be done, it is frequently possibleto determine its percentage composition with con-siderable accuracy. It is not, unfortunately, possiblein many cases to determine a mineral by blowpipetests alone; these must be considered in connectionwith the physical characteristics before a reliabledecision as to the correct name can be safely made.There are, however, a considerable number ofminerals with unique groups of constituents whichmay be determined by blowpipe analyses, and itis hoped that the following table will prove usefulin this respect. It includes most of the importantores and some of lesser importance, as well as anumber of gangue minerals, but some very importantores are omitted as well as a great number of commonminerals for the reason that blowpipe tests arelittle or no aid in their recognition. In a large

50


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DETERMINATION OF MINERALS 51number of cases two or more minerals on this tableyield tests for identically the same elements. Suchsubstances can be readily distinguished by theirappearance or by simple physical tests. For thispurpose almost any book on mineralogy will answer,but the author naturally prefers his own work,A Pocket Handbook of Minerals, published byJohn Wiley & Sons, New York, which places allthe emphasis upon the physical distinctions.

In the following table the chemical formula isplaced in parentheses after the name of each min-eral. By applying the principles presented inChapter VI it should be a comparatively simplematter to compute the percentage of any or allelements present in any mineral of fixed composition.The letters to the left of each name are the symbolsof the elements that may be found by means of theblowpipe; in comparatively few cases do they con-stitute all the elements present in the mineral beforewhich they stand, but the remainder fail to givesatisfactory tests with the blowpipe.The name of a mineral is repeated under eachelement for which it yields blowpipe tests. Water

(H2O) is treated as an element.Aluminum.

Al Corundum (A12O 3)Al, Li Spodumene (LiAlSi2OG).Al, P, H2O Turquois (AIPO4.A1(OH)3+ Cu).


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52 BLOWPIPE ANALYSISAl, K Orthoclase (KAlSi3O8).A1,S,H2O Alunite (K2SO4.3A12O3.3SO3.6H2O) (Al, H2O Bauxite (A12O3 + 2H2O).Al, H2O Kaolin (Al2Si2O7 + 2H2O).

Antimony.Sb Native Antimony (Sb).Sb Cervantite (Sb2O 4).Sb, As Allemontite (SbAs).Sb, Cu, S Tetrahedrite (Cu8Sb2S 7).Sb, Pb, S Jamesonite (Pb2Sb2S 5).Sb, Ag, S Pyrargyrite (Ag3SbS3).Sb, Ag, S Stephanite (Ag5SbS4).Sb, S Stibnite (Sb2S3).

Arsenic.As Native Arsenic (As).As, Sb Allemontite (AsSb).As, Co Smaltite ((Co,Ni) As2).As, Co, S Cobaltite (CoAsS).As, Cu, S Tennantite (Cu8As2S 7).As, Cu, S Enargite (Cu3AsS4).As, Cu, H2O Olivenite (Cu4As2O9 +H2O).As, Cu, H2O Conichalcite ((Cu,Ca) 4As2O9 -h

3/2H20).As, Fe Lollingite (FeAs2).As, Fe, S Arsenopyrite (FeAsS).As, Ni Niccolite (NiAs).As, Pb Mimetite (PbCl2.3Pb3As2O8.).As, Ag, S Proustite (Ag3AsS3 ).


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DETERMINATION OF MINERALS 53As, S Realgar (As2S2).As, S Orpiment (As2S3).

Barium.Ba Witherite (BaCO3).Ba, S Barite (BaSO4).

Bismuth.Bi Native Bismuth (Bi).Bi Bismite (Bi2O3).Bi, S Bismuthinite (Bi2S3).Bi, Te Tetradymite (TeBi).Bi, H2O Bismutite (Bi2CO 5 +H2O).

Boron.B Boracite (Mg7Cl2Bi6O30).B, Na, H2O Borax (Na2B 4O 7 -fioH2O).B, H2O Colemanite (Ca2B6On + 5H2O).

Cadmium.Cd, S Greenockite (CdS).

Calcium.Ca Calcite (CaCO3).Ca, F Fluorite (CaF2).Ca, Mg Dolomite ((Ca, Mg) CO3).Ca, P Apatite (Ca (Cl, F) 2.3Ca3P2O8).Ca, S Anhydrite (CaSO 4).Ca, S, H2O Gypsum (CaSO 4 + 2H2O).

Chromium.Cr, Fe Chromite (FeCr2O 4).Cr, Pb Crocoite (PbCrO 4).


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54 BLOWPIPE ANALYSISCobalt.

Co, As Smaltite ((Co, Ni) As2).Co, As, S Cobaltite (CoAsS).

CopperCu Native Copper (Cu).Cu Cuprite (Cu2O).Cu Tenorite (CuO).Cu Atacamite (CuCl2.3Cu(OH) 2).Cu, Sb, S Tetrahedrite (Cu8Sb2S 7).Cu, As, S Tennantite (Cu8As2S 7).Cu, As, S Enargite (Cu3AsS4).Cu, As, H2O Olivenite (Cu4As2O9 +H2O).Cu, As, H2O Conichalcite ((Cu, Ca) 4As2O9 4

3/2H20).Cu, Fe, S Bornite (Cu5FeS4).Cu, Fe,S Chalcopyrite (CuFeS2).Cu, S Chalcocite (Cu2S).Cu, S Covellite (CuS).Cu, S, H2O Chalcanthite (CuSO 4 + 5H2O).Cu, H2O Malachite (Cu2CO4 +H2O).Cu, H2O Azurite (Cu3C2O 7 +H2O).Cu, H2O Chrysocolla (CuSi

Fluorine.F, Ca Fluorite (CaF2).F, Na Cryolite (Na3AlF6).

Gold.Au Native Gold (Au,.Au, Te Calaverite (AuTe2).


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DETERMINATION OF MINERALS 55Iron.

Fe Hematite (Fe2O3).Fe Magnetite (Fe3O 4).Fe Siderite (FeCO3).Fe, As Lollingite (FeAs2).Fe, As, S Arsenopyrite (FeAsS).Fe, Cr Chromite (FeCr2O4).Fe, Mn, Zn Franklinite ((Fe, Zn, Mn) 3O 4).Fe, P, H2O Vivianite (Fe3P2O8+8H2O).Fe, S Pyrrhotite (FenSn+I).Fe, S Pyrite (FeS2).Fe, Ti Ilmenite (FeTiO3).Fe, H2O Limonite (2Fe2O3 +3H2O).

Lead.Pb Cerussite (PbCO3).Pb, Sb, S Jamesonite (Pb2Sb2S 5).Pb, As Mimetite (PbCl2.3Pb3As2O8 .).Pb, Cr Crocoite (PbCrO 4).Pb, Mo Wulfenite (PbMoO 4).Pb, P Pyromorphite (PbCl2.3Pb3P2O8).Pb, S Galenite (PbS).Pb, S Anglesite (PbSO 4).Pb, V Vanadinite (PbCl2.3Pb3V2O8).Pb, V, etc. Uraninite (?).

Lithium.Li, Al Spodumene (LiAlSi2Oe).

MagnesiumMg Magnesite (MgCO3).


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56 BLOWPIPE ANALYSISMg, Ca Dolomite ((Mg, Ca)CO3).Mg;H2O Talc (Mg3Si4On+H2O).

Manganese.Mn Pyrolusite (MnO2).Mn Rhodochrosite (MnCO3).Mn Rhodonite (MnSiO3).Mn, Fe, Zn Franklinite ( (Mn, Fe, Zn) 3O4).Mn, S Alabandite (MnS).Mn, H2O Manganite (Mn2O3 +H2O).Mn, H2O Psilomelane (MnO2 + 2H2O).

Mercury.Hg Native Mercury (Hg).Hg, S Cinnabar (HgS).

Molybdenum.Mo Molybdite (MoO3).Mo, Pb Wulfenite (PbMoO4).Mo, S Molybdenite (MoS2).

Nickel.Ni, As Niccolite (NiAs).Ni, S Millerite (NiS).Ni, H2O Garnierite (H2 (Ni, Mg)SiO4 -fH2O)

Phosphorus.P, Al, H2O Turquois (A1PO 4.A1(OH)3 +H2O + Cu).P, Ca Apatite (Ca(Cl, F) 2 . 3Ca3P 2O8).P, Fe, H2O Vivianite (Fe3P2O8 + 8H2O).P, Pb Pyromorphite (PbCl2.3Pb3P2O8).


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DETERMINATION OF MINERALS 57Potassium.

K Sylvite (KC1).K, Al Orthoclase (KAlSi3O8).

Selenium.Se, Pb Clausthalite (PbSe).

Silver.Ag Native Silver (Ag).Ag Cerargyrite (AgCl).Ag, Sb, S Pyrargyrite (Ag3SbS3).Ag, Sb, S Stephanite (Ag5SbS4).Ag, As, S Proustite (Ag-jAsSa).Ag, Te Petzite ((Ag, Au) 2Te).Ag, Te Sylvanite ( (Ag, Au)Te2).Ag, S Argentite (Ag2S).Ag, Te Hessite (Ag2Te).

SodiumNa Halite (NaCl).Na, B, H2O Borax (Na2B 4O 7 + ioH2O).Na, F Cryolite (Na3AlF6).Na, S Thenardite (Na2SO4).Na, H2O Natron (Na2CO3 + ioH2O).Na, H2O Trona (Na2CO 3.HNaCO 3 +2H 2O).

StrontiumSr Strontianite (SrCO3).Sr, S Celestite (SrSO 4).


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58 BLOWPIPE ANALYSISSulphur.

S Native Sulphur (S).S,Al,H2O-Alunite(K2SO 4.3Al2O3.3SO3.6H2O),S, Sb Stibnite (Sb2S3).S, Sb, Cu Tetrahedrite (Cu8Sb2S 7).S, Sb, Pb Jamesonite (Pb2Sb2S5).S, Sb, Ag Pyrargyrite (Ag3SbS3).S, As Realgar (As2S2).S, As Orpiment (As2S3).S, As, Cu Tennantite (Cu8As2S7).S, As, Cu Enargite (Cu3AsS4).S, As, Fe Arsenopyrite (FeAsS).S, As, Ag Proustite (AggAsSs).S, Ba Barite (BaSO4).S, Bi Bismuthinite (Bi2S3).S, Cd Greenockite (CdS).S, Ca Anhydrite (CaSO4).S, Ca, H2O Gypsum (CaSO4 + 2H2O).S, Cu Chalcocite (Cu2S).S, Cu Covellite (CuS).S, Cu, Fe Bornite (Cu 5FeS4).S, Cu, Fe Chalcopyrite (CuFeS2).S, Cu, H2O Chalcanthite (CuSS, Fe Pyrrhotite (FenSn+ i).S, Fe Pyrite (FeS2).S, Pb Galenite (PbS).S, Pb Anglesite (PbSO 4).S, Mn Alabandite (MnS).S, Mo Molybdenite (MoS2).


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DETERMINATION OF MINERALS 59S,Ni Millerite (NiS).S, Ag Argentite (Ag2S).S, Na Thenardite (Na2SO4).S, Sr Celestite (SrSO 4).S, Zn Sphalerite (ZnS).

Tellurium.Te Native Tellurium (Te).Te, Bi Tetradymite (BiTe).Te, Au Calaverite (AuTe2).Te, Ag Petzite ((Au, Ag) 2Te).Te, Ag Hessite (Ag2Te).Te, Ag Sylvanite ((Au, Ag)Te2).

Tin.Sn Cassiterite (SnO 2).

Titanium.Ti Rutile (TiO2).Ti Titanite (CaTiSiO 5).Ti, Fe Ilmenite (FeTiO3).

Tungsten.W Scheelite (CaWO 4).Uranium.

U, Pb, etc. Uraninite (?).Vanadium.

V, Pb Vanadinite (PbCl2.3Pb3V2O8)oZinc.Zn Zincite (ZnO).

Zn Smithsonite (ZnCOs).


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60 BLOWPIPE ANALYSISZn Willemite (Zn2SiO4).Zn, Fe, Mn Franklinite ((Zn, Fe, Mn)3O4).Zn, S Sphalerite (ZnS).Zn, H2O Hydrozincite (3ZnCO3 + 2H2O).Zn, H2O Calamine (Zn2SiO4 +H2O).

Water.H2O, Al Bauxite (A12O3 + 2H2O).H2O, Al Kaolin (Al2Si2O 7 + 2H2O).H2O, Al, P Turquois(AlPO 4.Al(OH)3 -fH2O +Cu).H2O,A1,S Alunite(K2SO4.3Al2O3.3SO3.6H2O).H2O, As, Cu Olivenite (Cu4As269+H2O).H2O, As, Cu Conichalcite ((Cu, Ca) 4As2O 9 +3/2H20).H2O, Bi Bismutite (Bi2CO5 +H2O).H2O, B Colemanite (Ca2B 6On + 5H2O).

H2O, B, Na Borax (Na2B 4O 7 + ioH2O).H2O, Ca, S Gypsum (CaSO 4 + 2H2O).H2O, Cu Malachite (Cu2CO4 +H2O).H2O, Cu Azurite (Cu3C2O 7 +H2O).H2O, Cu Crysocolla (CuSiO3 + 2H2O).H2O, Fe Limonite (2Fe2O3 +3H2O).H2O, Fe, P Vivianite (Fe3P2O8 +8H2O).H2O, Mg Talc (Mg3Si4On+H2O).H2O, Aln Manganite (Mn2O3 +H2O).H2O, Mn Psilomelane (MnO2 + 2H2O).H2O, Ni Garnierite (H2 (Ni, Mg)SiO4 +H2O).H2O, Na Natron (Na2CO3 + ioH2O).H 2O, Na Trona (Na 2CO3.HNaCO 3 -f 2H 2O).


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DETERMINATION OF MINERALS 61H2O, Zn HydrozinciteH2O, Zn Calamine (Zn2SiO4 +H2O).

Silicates.The two mentioned below are the only ones in the

above list which wilt give the test for a silicatedescribed previously.

Willemite (Zn^SiO4).Calamine (Zn2SiO4 +H2O).

Carbonates.Ba Witherite (BaCO3).Bi Bismutite (Bi2CO 5 +H2O).Ca Calcite (CaCO3).Ca, Mg Dolomite ((Ca, Mg)CO3).Cu, H2O Malachite (Cu2CO 4 +H2O).Cu, H2O Azurite (Cu3C2O 7 +H2O).Fe Siderite (FeCO3).Pb Cerussite (PbCO3).Mg Magnesite (MgCO3).Mn Rhodochrosite (MnCO3).Na, H 2O Natron (Na2CO3 + ioH2O).Na, H 2O Trona (Na2CO3.HNaCO3 +2H2O).Sr Strontianite (SrCO3).Zn Smithsonite (ZnCO3 ).Zn, H2O Hydrozincite


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CHAPTER VITHE ELEMENTARY PRINCIPLES OF CHEMISTRY

THE USE AND INTERPRETATION OF CHEMICALSYMBOLSElements. Every body in nature is composed

of one of more constituent substances called elements.Sometimes, as in the case of the metals gold, silver,and copper, there is only one substance; it is itselfan element. In other cases there are two or moreelemental constituents present in the body, which byproper manipulation may be broken up or resolvedinto its elements.An element, is then, something that has resisted

all attempts to subdivide it into other substances.It follows, necessarily, that an element cannot beformed by a union of other substances.Each element differs more or less from all others

in appearance, properties, and uses. Some aregases, some are opaque and reflect light from thesurface are metals, and some are transparent ortranslucent are non-metals. The distinction be-tween metals and non-metals is, however, notsharply marked, since there are elements with inter-

62


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ELEMENTARY PRINCIPLES OF CHEMISTRY 63mediate properties. A full list of all known elementsis given in the table at the end of this chapter.

It has happened occasionally that a substancesupposed to be an element has been found to becomposed of two or more elements, and this willprobably occur in the future, but chemists feelpractically certain of the elementary condition of allthe commoner elements. They know now that theAlchemists' search for a method of making goldwas foredoomed to failure.

Chemicarl Compounds. Elements have the prop-erty of uniting under certain conditions to formnew substances, differing in nature from any ofthe constituent elements. The results of such unionsare not merely mechanical mixtures of the elementsin which each component can be identified underthe high-power microscope, but are homogeneoussubstances of definite properties, which will oftenfail to respond to tests yielded by their constituentelements. Such combinations of two or moreelements are called chemical compounds. Thus,the common chemical compound water is composedof one gas, hydrogen, which burns in the air, andanother, oxygen, which is essential for respiration,properties quite foreign to water.Most natural bodies are either chemical compounds

or mixtures of them. Other peculiarities possessedby them will be mentioned later.

Alloys. Alloys are rather indefinite compounds


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64 BLOWPIPE ANALYSISof metals whose natures are not thoroughly under-stood.Atoms. Atoms are the smallest particles into

which it is believed an element may be divided andstill retain all its distinguishing properties. Althoughnot infinitely small, they are far too minute to beseen with the microscope, yet there are abundantmore or less indirect proofs of the correctness ofthe atomic theory. That atoms are themselvessubdivisible is now admitted, but these lesser par-ticles reveal the characteristic properties 'of entirelydifferent elements from those which they formedbefore disintegration, and are produced only undervery unusual conditions, probably never, or veryrarely, duplicated in chemical operations.

According to the atomic theory, the atoms of anyelement have the same weight and size and areidentically alike, while the atoms of different ele-ments have different weights and sizes, and furtherdiffer to the same extent as do the elementsthemselves.

Molecules. Molecules are the smallest particlesinto which it is believed a chemical compound maybe divided and still remain the same chemicalcompound. They must consist, evidently, of at leasttwo, and often several, atoms. The same word(molecule) is also applied to the smallest volumesof a gas, even though it be an element instead of acompound, since it appears certain that the smallest


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ELEMENTARY PRINCIPLES OF CHEMISTRY 65particles of gases always consist of at least twoatoms.With certain modifications that it is not necessary

to discuss, it may be stated that the number ofatoms present in a molecule of a given chemicalcompound is always the same, and that the differentatoms forming a molecule of a certain chemicalcompound are always present in a fixed proportion.Thus, a molecule of water always contains twoatoms of hydrogen and one atom of oxygen.

Symbols. For convenience, the elements arerepresented by the initial letter, either alone or withan added letter, of their Latin or Greek names,which are in many cases very similar to their Englishnames. These letters are called the symbols ofthe elements.aFormulae. The formula of a chemical compoundis written by placing the symbols of its component

elements in a line, and, if more than one atom ofany of these is present in the molecule of the com-pound, the number of such atoms is indicated bysubscripts written after the symbols of the elementsthus affected. Thus, the formula of water is H2O,indicating that the molecule of water contains twoatoms of H combined with one atom of O. Thisformula is read h-two-o.

It is sometimes possible to group the atoms inthe formula of a complex substance in such a fashionas to form two or more groups of molecules, indicat


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66 BLOWPIPE ANALYSISing that the substance may be formed not only bya union of atoms but also by a combination ofmolecules. Such formulae may be written with aperiod separating the constituent molecules. Thus,CaCOs (read c-a-c-o-three) is the symbol of calcite,of which marble is a variety, and this formula maybe written CaO.CO2 , indicating that the materialis formed by the union of one molecule of lime(CaO) and one of carbonic acid gas (CO2). Whenit is possible to break up a formula into moleculesin this way, it is often found that more than oneof a certain constituent molecule is present insubstance. Thus, the ordinary formula of ortlio-clase feldspar is KAlSiaOg, but, after multiplyingeach atom by two, this is found to consist of onemolecule of potassium oxide (K2O), one of alumina(A12O3), and six of silica (SiO2), and may thereforebe written K2O.Al2O3.6SiO2 . The order in whichthe different molecules are written is of no greatimportance; the above formula might with equalcorrectness be written 6SiO2.K2O.Al2O3, althoughthis is not the customary order. It should benoticed that a figure prefixed to a molecule, as inthe case of the 6 in the above formula, applies onlyto the molecule to which it is prefixed.

Sometimes formulae like the following (the formulaof emerald) are used: Be3Al2 (SiO3)6. This is readb-e-three-a-1-two - parenthesis-s - i-o - three - taken - six-times. Both the Si and the O in the parenthesis are


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ELEMENTARY PRINCIPLES OF CHEMISTRY 67affected by the subscript 6 and might be writtenSi6Oi8 , but it is sometimes desirable to group ele-ments in parentheses in this way. Groups like thisare not molecules since they do not occur as knownchemical compounds.A different use of the parenthesis is seen in thecase of those compounds in which the relative pro-portions of certain compounds are apt to varyapparently a modification or violation of a previouslyexpressed law. Thus, a common constituent oflimestone is a mineral called dolomite, whose formulais (Mg,Ca)COs. Here the comma between theMg and Ca indicates that the relative proportionof Mg and Ca is not fixed; there may be a nearlyor quite equal number of atoms of both present,or either may predominate to a small or greatextent over the other. In an instance like this theelement first written in the parenthesis is apt to bethe more plentiful. Sometimes it is more con-venient (as when the horizontal space is limited)to write the variable elements in such formulae in avertical column without using the comma, in this/Mg Nmanner: I (Atomic weights. The atomic weight of an

element is the relative weight of an atom of theelement compared with the weight of an atom ofH, which is taken as unity, it being the lightestknown element. Thus, an atom of Fe is fifty-six


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68 BLOWPIPE ANALYSIStimes as heavy as an atom of H, so the atomic weightof Fe is 56. A presentation of the methods bywhich the atomic weights of the various elementsare determined is not necessary, but these atomicweights have a practical use which is important.This may be illustrated as follows: Since purewater is composed entirely of molecules havingthe formula H2O, if we know the relative weightsof the H and O atoms, it should be a simplematter to calculate the proportions by weight ofH and O in the molecule, and thus to determinethe proportion by weight of these elements in anyamount gf the substance. There being two atomsof H present in the molecule, each of whichweighs one unit (atomic weight of H is i),and one atom of O, which weighs sixteen units(atomic weight of O is 16), the whole moleculemust weigh 2 + 16=18 units. It is plain thatthe H must constitute 2/i8 , or l/9 , and the Oform 16/is> or 8/9 of the whole molecule. It fol-lows that pure water in any amount is 1/9 H and8/9 o.

In this way it is always possible to calculate therelative proportions of the different elements in asubstance whose formula is known, provided noelements involved occur in variable quantities,indicated by placing them, separated by commas,in parentheses, or in vertical columns in parentheses,as previously explained. The atomic weights of


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ELEMENTARY PRINCIPLES OF CHEMISTRY 69all the elements are given in the table at the endof this chapter.

Suppose, for illustration, it be required to findhow many pounds of each of the component elementsthere are in 100 pounds of pure marble, with theformula CaCO3 . Let the abbreviation A.W. meanatomic weight, thenA.W. Ca = 40. Total weight of the one Ca atom= 40 H units.A.W. C=i2. Total weight of the one C atom= 12 H units.A.W. O = i6. Total weight of the three O atoms= 48 (3X16) H units.Total weight of the molecule = 100 H units.Ca present is 4%oo of whole =40% = 40 pounds.C present is 12/ioo of whole = 12%= 12 pounds.O present is 48/ioo of whole =48% = 48 pounds.As a still more complex case, let it be required

to ascertain the amount of Zn and H2O in 100 poundsof hydrozincite, with the formula jZnCOs +2H2O.A.W. Zn=-654. Number of atoms of Zn = 3.

Weight of three Zn atoms (3X65.4) = 196.2.A.W. C = i2. Number of atoms of = 3. Weight

of three C atoms (3 X 1 2) = 36.A.W. O = 16. Number of atoms of O =

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Butler Pocket Handbook of Blowpipe Analysis