820

C H E M I CA L S & M AT E R I A L S A F E T Y DATA S H E E T S ( M S D S ) MSDS Online

http://www.msdsonline.com

This is an online resource for all MSDS and Chemical Abstracts Services (CAS) information. You will have to register, but it only takes a minute.

MSDS.comhttp://www.msds.com

Periodic Table of Elementshttp://www.webelements.com

This site has information regarding the periodic table of elements.

A F E W B A S I C C H E M I S T RY D E F I N I T I O N SACIDS: Acids are compounded solutions with a pH of less than 7. Acids neutralize alkalis

such as developers. An acid will turn a blue litmus paper a pink-red. Acids are compounds

containing hydrogen that can be replaced by a metal to form a salt; that is, the metal sodium

will replace the hydrogen atom in hydrochloric acid to form the salt, sodium chloride. Acid

strength affects two of the most common functions: imparting a sour taste and creating an

acid environment to limit microbial growth.

NOTE ON ACIDS AND WATER: Heat is released when strong acids are mixed with

water and increasing the amount of acid adds to the level of that heat, releasing more heat. If

you add water to acid, you will create an extremely concentrated solution of acid immediately

at the point of the addition. So much heat is released that the solution may actually boil vio-

lently, causing eruptions of concentrated acid. Conversely, if you add acid to water, the solu-

tion that forms at the point of the addition is very dilute, and the level of heat released is not

sufficient to cause a violent reaction. Remember Triple A . . . Always Add Acid to water and

never the reverse.

A

Chemical Safety Considerations, Definitions, Information, Small Volume Conversions and Formulas

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ALKALIS: Alkalis are compounded solutions with

a pH greater than 7. Alkalis are the assorted soluble

metallic hydroxides that neutralize acids to form salts.

An alkali can also be a compounded salt. It functions

as an accelerator in photographic developing formulas

(often potassium and sodium hydroxide). Alkalis turn

red litmus paper blue. Examples of alkalis are sodium

carbonate and borax.

ANHYDROUS: Meaning a solid substance

without water or crystallization.

BASE: Bases are the chemical opposite of acids

and react with acids to produce water and to form salts

(or their solutions). Some general properties of bases

include bitter taste, slick texture (like soap and water),

violent reaction with acids, caustic to organic matter,

and turning red litmus paper blue. A base is a substance

that will neutralize an acid but will not dissolve in water

APP–1Jacquie Mahan, Self as Kid, 2003Jacquie graduated from the Art Institute of Boston a few years ago and went on to own and operate the Mahan Gallery in Columbus, Ohio, which was recognized as one of the most influential new galleries in the United States. This self-portrait explains a lot about her sense of humor and her experiences in junior high.(Courtesy of the Artist)

(e.g., iron and copper). A base that dissolves in water is

called an alkali (e.g., sodium carbonate).

BUFFER: Weak acid(s) or base(s) dissolved

in water that hold the pH near to a constant value

when an acid or base is added. Buffering is the abil-

ity of a weak acid/salt combination, such as citric

acid and sodium citrate, to control the amount of

free hydrogen ions. When certain amounts of acid

or base are added, the system resists changes in pH.

Citric acid has the widest effective buffer range—from

pH 2.5 to 6.5. Tartaric acid can only be used for buff-

ering between pH 3.0 and 4.5.

DELIQUESCENT: A deliquescent chemical is

one that readily absorbs moisture from the air. Salts

are a prime example.

pH: one explanation of the acronym pH is that it’s

an early twentieth-century acronym from the German

word potenz (meaning “power”) and hydrogen, or the

power of hydrogen. A pH number designates a numer-

ical value assigned to an aqueous solution to indicate

that it is either acidic or alkaline. It also represents a

chemical symbol for the logarithm of the reciprocal

of the hydrogen ion concentration in gram atoms per

liter. What you need to know, in the context of this

book, is that it informs you of the acidity or alkalinity

of the chemistry you are using.

SALT: A salt is formed when an acid and a

base are mixed and the acid releases H+ ions, while

the base releases oH– ions. This process is called

hydrolysis and creates an ionic compound. The pH of

the salt depends on the strengths of the original acids

and bases:

Acid Base Salt pH

strong strong pH = 7

weak strong pH > 7

strong weak pH < 7

weak weak depends on

which is stronger

SATURATED SOLUTION: Definition of a solu-

tion that cannot accept any more solid (solute) at a

given temperature without leaving sediment in the

solution. An example of this is the preparation of

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saturated potassium or ammonium dichromate for

gum bichromate sensitizing (e.g., potassium dichro-

mate saturates at 10%–13%).

SOLUBILITY: The maximum weight of a sub-

stance that will dissolve completely in a given volume

of solvent and at a specific temperature.

SURFACTANT: An agent, such as Tween, that

reduces the surface tension of a liquid, enabling it to

more easily penetrate a paper substrate.

H OW C H E M I CA L S CA N A F F E C T T H E B O DY ♦ Breathing: Airborne chemical matter and vapors

in the form of gases can enter the body through your

nose and mouth. Work in a well-ventilated environ-

ment, preferably outdoors or using ventilation that

will not pull the vapors past your face on their way

to an exhaust fan. Paper painter’s masks offer only

modest protection against chemicals and practically

none against harmful fumes.

♦ Ingestion: It is a bad idea to eat while work-

ing in the lab, or with chemistry, because you are

quite likely going to ingest that same chemistry. Eat

somewhere else.

♦ Absorption: Chemistry can enter the body

through the skin and get into the bloodstream.

open cuts or healing wounds on your skin can be

an avenue for absorption as well. Wear barrier

gloves and a mask when mixing chemistry. Gloves

may present a number of problems. Commonly

available types are made from a variety of materi-

als, not all of which provide an adequate barrier

from specific chemicals. Gloves made of nitrile,

available from laboratory and chemical supply

houses, work well for most chemicals that you will

use in alternative process. Except for mild chemi-

cal usage, avoid latex or kitchen gloves, because

these are susceptible to chemical reactions and

are often clumsy.

Protecting Yourself: Be Prepared

The key to chemical safety is controlling the degree

of exposure to the hazards encountered in the mix-

ing and use of all chemistry. Ingestion and absorp-

tion are easy to protect against in a working lab, it’s

simply common sense. However, if you are working

in a home lab, and you have children or pets, it is

imperative that you store your chemistry in a safe

and secure place. Prohibit any eating, drinking, and

splashing in the toning area. Prevent skin absorption

by keeping chemicals from contacting the skin or

eyes. If you have sensitive skin, or your skin has cuts,

or abrasions, protect it with some type of separation

such as tongs, splash goggles, and nitrile gloves.

Safety goggles are essential when mixing powdered

chemistry, because eyes will readily absorb and pass

contaminants along to the rest of the body. If you

wear contact lenses, be extra cautious to prevent the

powders and chemical fumes from getting between

your contact lenses and your eyes.

IF YOU ARE WORKING WITH DANGEROUS

CHEMICALS, HAVE THE SOLUTION TO AN

ACCIDENT ON HAND. An example of this would be

if you were using potassium cyanide (KCN) as a fixer for

wet plate collodion. It would be essential that you have

several bottles of 3% hydrogen peroxide (drugstore vari-

ety) with you to convert a dangerous spill to an inconse-

quential one. Hydrogen peroxide will change potassium

cyanide (health hazard level 3) to a harmless potassium

cyanate (health hazard level 1). The ratio for this con-

version is 6 parts hydrogen peroxide to 10 parts potas-

sium cyanide. If you splash or spill KCN on your skin,

don’t take time measuring the proportions; just flood

the area of the splash with hydrogen peroxide several

times and wash with water.

F I R S T A I DFirst Aid for Ingestion of Acids and Alkalis

Curiously, the signs and symptoms for ingestion of

acids and alkalis are quite similar, as are the recom-

mendations for treatment. In the past, if an acid was

swallowed, the immediate response was to neutralize

the acid with an alkali drink (e.g., sodium bicarbonate,

several glasses of milk or milk of magnesia, or eight

to twelve antacids). If an alkali was not at hand, then

the response was to force the victim to rinse the mouth

area repeatedly.

Symptoms and signs associated with significant

alkali-induced tissue injury include pain in the mouth

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and throat, drooling, pain on swallowing, vomiting,

abdominal pain, and hematemesis . . . a nice way to

say vomiting of blood. If the larynx is involved, local

edema may produce respiratory distress and a hoarse

voice. Veterinarians recommend giving a solution of

one part vinegar to four parts water. Rinse the mouth

with water or saline solution and call for medical assis-

tance in either acid or alkali events.

There is disagreement over the effectiveness of

having the victim drink large quantities of water. My

friend Dr. Jacek Mostwin, at Johns Hopkins, says that

the water simply makes the injury spread and that acid

or alkali ingestion is not really a first aid situation at

all . . . you need professionals right away. one thing is

for sure . . . DO NOT INDUCE VOMITING. This is

especially true for hydrofluoric acid ingestion.

That said, here are the basic immediate first aid

recommendations for both acid and alkali ingestion:

♦ Do NoT induce vomiting.

♦ Do NoT attempt neutralization.

♦ Do NoT give oral fluids.

♦ Do NoT give activated charcoal (for alkali).

♦ Do rinse the mouth with saline or water for acid.

♦ Do remove visible material from mouth with water

or saline (for alkali).

♦ Do call 911 and request immediate medical assistance.

First Aid for Skin Contact

If an acid or corrosive chemical is splashed on the

skin, immediately proceed to the nearest sink, or

emergency shower, and flush the affected area for at

least 15 minutes. If the chemical is on your clothing,

remove all contaminated clothing.

If a chemical splashes in the eye the immediate

response is to flush the eye repeatedly with warm water

or first aid saline solution eyewash. If an acid, make a

very dilute solution of sodium bicarbonate and use that

as well. If an alkali, repeatedly flush with water, or saline

solution, and rinse with a very dilute solution of boric

acid. In all cases, call for professional medical help.

Seek Emergency Medical Assistance If:

1. The victim has signs of shock, such as fainting,

pale complexion, or breathing in a notably

shallow manner.

2. Thechemicalburnpenetratedthroughthefirst

layer of skin, and the resulting second-degree

burn covers an area more than 2–3 inches in

diameter.

3. The chemical burn occurred on the eye, hands, feet,

face, groin, or buttocks, or over a major joint.

Poison Control Telephone: 1-800-222-1222

If you’re unsure whether a substance is toxic, call the

poison control center at this number: (800) 222-1222.

This is the telephone number for every poison center

in the united States. Call this number 24 hours a day,

7 days a week to talk to a poison expert. If you seek

emergency assistance, bring the chemical container or

a complete description of the substance with you for

identification.

C H E M I S T RY & S A F E T Y ♦ Do not place an exhaust vent above your face. If

you are building a darkroom, install the exhaust in

the floor or, better yet, do as we do at the College

of Art and Design at lesley university and build

your ventilation system into the sink itself so that

the fumes are vented before reaching your face.

Having an exhaust above your face just pulls all

of the fumes past your eyes, nose, and mouth on

their way to the vents. The fan and exhaust capac-

ity should be able to completely exchange the air in

the room every 3–6 minutes. Consult with an air

quality company for the specifics that will be best

for your space.

♦ Prevent chemical material from becoming airborne

through careful handling and mixing of liquids and

powders. Work slowly and don’t splash.

♦ Cover trays and tanks when not in use to prevent

vapors from filling your working space. Sheets of

Plexiglas® work well. label each sheet with the

chemical that it covers so that it is always used for

the same chemicals.

♦ Triple A. When mixing, Always Add Acid to

water; never add water to acid. In this way,

which is the only way, heat produced by the acids

will not cause a splattering acidic liquid eruption.

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♦ When weighing chemicals on digital gram scales,

never place raw chemicals on the weighing platform

of the scale. Always place a weighing paper or a

plastic/paper cup on the scale to hold the chemistry.

Always weigh the paper or cup before depositing

the chemical, and re-calibrate your scale to zero by

pressing “TARE” so that the chemical weight will be

the only thing being weighed.

♦ Prior to working with any chemical that you are not

familiar with, be sure to read the chemical’s MSDS

data sheet to understand its traits and how to deal

with it in the event of an accident or emergency. Mix

chemistry in glass or plastic containers—never metal.

♦ Always wear gloves and safety glasses when weighing

and mixing chemistry.

♦ Always use a plastic funnel to prevent spilling and

splashing when transferring chemistry, solids, or

solutions.

♦ Always clean all utensils and equipment that have

been in contact with chemistry.

♦ Always keep your mixed chemistry in labeled and

sealed containers.

♦ Never keep your chemistry in a location that will

be accessible to children, pets, and guests. In other

words, do not store your chemistry in your home

refrigerator, whether it is labeled or not. If your

chemistry needs to be refrigerated, buy a small

dorm-type unit for your lab and lock it.

♦ Always mix chemical formulas in the order that the

components are listed. There are exceptions to this,

but those exceptions should be noted along with the

ingredients in the formulas.

♦ Always have 911 or poison control numbers posted

in your lab.

♦ As an artist, your eyes are your life. You must have

an eyewash kit in your lab.

X Note: Please be aware that all chemicals

are hazardous in one form or another, and

any concerns you may have regarding their

use and dangers can be found by accessing

MSDS web sites or by requesting MSDS

data sheets from the companies that sup-

ply you with chemistry. If you intend to use

any of these chemicals in a class situation, it

is imperative and mandatory that you have

MSDS data sheets on hand in the event of an

emergency.

Dichromates: Safety and Disposal

Dichromates—ammonium, potassium, and sodium

versions—are potentially hazardous chemicals,

and care should be taken in both their use and dis-

posal. Be very careful to avoid breathing a dichro-

mate dust, because it is toxic, and allowing the

chemical to come in contact with your skin. Do not

touch your skin, mouth, or eyes when working with

any dichromate, and if you experience a problem

(burning, coughing, difficulty breathing, vomiting,

cramps, blurred vision, etc.), flush the problem-

atic area with lots of water for 15 minutes and seek

immediate medical attention. If a dichromate spills

on your clothing, remove that article of clothing

and wash it well before putting it back on. Wear

gloves when working with this chemical. Be espe-

cially careful around high-heat sources because this

chemical’s reaction to heat can be quite intense as it

decomposes.

Proper disposal of dichromate solutions is important.

As a rule, never throw loose and dry orange dichro-

mate/bichromate crystals in the trash. Very small

amounts of solution can be disposed of by dilution with

copious amounts of water and flushed away. larger vol-

umes of dichromate are a different matter. one method is

to add used developer to a dichromate solution. Another

is to make the solution alkaline by adding baking soda to

the solution. This change can be detected by using litmus

paper that will turn blue in a base or alkali. once the solu-

tion is alkaline, pour it through several layers of coffee

filters. The liquid will be free of the chromium and then

flushing of the liquid can take place. The sludge in the

coffee filters must be disposed of by a hazardous waste

facility. Check with local college photo lab managers to

get the names of these facilities.

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C H E M I CA L A B S T R A C T S E RV I C E R E G I S T RY ( CA S )The numbers following each chemical’s name are

part of a worldwide indexing system called Chemical

Abstracts Services Registry (CAS). It is used here to

ensure that everyone using a chemical is dealing with

the same one when describing it for any purpose. The

CAS numbers for these, and other chemicals on Earth,

can be found at various sites that offer CAS numbers.

C H E M I CA L SAcetic Acid CAS# 64-19-7

Acetic acid is a clear fluid and has a pungent vinegar-like

odor. It is used in 20%–28% dilutions for photographic

purposes, although a 33% solution is called for in calo-

type (stronger if the ambient temperature is hot). At

28% it is primarily used as a stop bath and is found in a

hardening fixer bath. It can also be used as a solvent of

gelatin and collodion. To prepare a photo-grade solu-

tion dilute 3 parts glacial acetic acid with 8 parts water.

A 5% variation is used to make pickles. I have heard

that a weak dilution is also used for treating sunburn,

but I wouldn’t recommend this idea without medical

advice. In high concentrations, both its vapors and

solution are corrosive and unpleasant for the skin and

respiratory system. In low concentrations it will make

your eyes sting and may cause an allergic reaction on

your skin. Vinegar is a 5% acetic acid. If you spill acetic

acid on your skin, wash well with clean water. Do not

drink acetic acid at any level stronger than vinegar. If

somehow you ingest a strong concentration, take milk

of magnesia and seek medical attention. Acetic acid is

incompatible with strong oxidizers (meaning that it

will generate heat), carbonates, hydroxides, and strong

alkalis (a violent reaction). Never expose acetic acid to

sodium peroxide or nitric acid because it may produce

an explosion. Dilute this chemical well before dispos-

ing.Storeitabove63˚Ftopreventitfromsolidifying.

X Note: Glacial acetic acid refers to a very

strong concentrated acetic acid, usually between

80% and 99%, with a pH of 2.4. At this concentra-

tion it is highly corrosive and is a severe poison.

Alcohol (Everclear)

Grain alcohol (95% 190-proof ethanol) can be diffi-

cult to locate. It is not available in all states. Everclear

brand grain alcohol can be purchased over the

Internet (http://www.shoppersvineyard.com). It can

also be purchased in liquor stores in several states

including New Mexico, where it is often included in a

wet plate collodion kit (as grain alcohol) from Bostick

& Sullivan. Do not drink this alcoholic liquid

alone or as a pea-brained additive to a punch-

bowl at a party.

Alum (Ammonium Alum, Ammonia Aluminum sulphate) CAS# 7784-26-1

This component is often found as a hardener for fixing

baths and gelatin, hypo-alum toner, and clearing

baths. Its fumes will cause distress to your respiratory

and intestinal tract, and contact will cause itching and

reddening to your skin. If it is ingested, do not induce

vomiting. Take normal safety precautions with gloves,

goggles, and a respirator.

Ammonia CAS# 7664-41-7

Ammonia is a corrosive gaseous fluid that can cause

severe burning reactions to the respiratory system,

eyes, and tissue. It is normally used in solution as

ammonium hydroxide. High degrees of exposure can

cause fatal reactions, including death. Be cautious

when using this chemical. There is a very strong

odor associated with it, and a dual-filter respirator is

advised. Be especially careful of getting this chemical

in your eyes because even the slightest amount will

cause severe problems—even with immediate first aid

treatment and wash.

X Note: Never mix ammonia with silver

nitrate or gold because it forms explosive azides.

Ammonium Carbonate CAS # 506-87-6

This chemical presents itself as a fine, white crystal

with a hint of ammonia in its odor. It is found most

often as an accelerator in warm-tone developers

and is not particularly dangerous. Vapors may cause

respiratory distress, and contact with eyes, mucous

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membranes, and skin will result in redness and irrita-

tion. It should be kept at a good distance from acids

and strong alkalis. use normal safety precautions.

Ammonium Chloride (Sal-Ammoniac) CAS# 12125-02-9

Ammonium chloride is a white crystal/powder used

as an accelerator in sodium thiosulphate fixing baths.

It is also employed in salted albumen papers. This

chemical is troublesome for the eyes and your respira-

tory system. It is important to know that heating this

chemical will cause a wispy smoke that is very unpleas-

ant (hydrochloric acid and ammonia). Ammonium

chloride will cause respiratory distress if inhaled. It

is not compatible with acid concentrates, potassium

chlorate, and ammonium nitrate. Wear a respirator,

safety glasses, and gloves when mixing.

Ammonium Citrate CAS# 12125-02-9

This chemical is a moderately safe one to work with.

Inhalation of the powder will cause respiratory distress

and is particularly problematic if it gets into your eyes,

causing redness and pain. Be careful not to inhale, ingest,

or rub this chemical on your skin. If you experience a bad

reaction to ammonium citrate on your skin or in your

eyes, flush well with water and seek medical attention.

Ammonium Dichromate (also Bichro-mate)CAS# 7789-09-5

This chemical is used in sensitizers for a number of

non-silver and alternative processes (gum bichromate

and carbon printing) and behaves in much the same

manner as potassium dichromate except that it is more

aggressive and becomes saturated at 25% versus 13%.

Potassium dichromate is preferred for gum bichro-

mate printing, as it renders more slowly and with

less contrast. Its crystals are orange in color and are

a strong irritant for literally every part of your being.

It can cause ulcerations on the skin and, if inhaled,

significant respiratory distress—especially in mucous

membranes. Ammonium dichromate is flammable in

a dry state, so do not throw out the powder with the

trash . . . over-saturate and flush for disposal.

Ammonium Ferric Oxalate CAS# 14221-47-7

(Ammonium iron (III) oxalate trihydrate)

like all oxalates, this chemical will be toxic to your

health and highly corrosive to skin, eyes, tissue, and

respiratory system. This chemical can be absorbed

in the body by breathing or ingesting and can cause

havoc with your kidneys. Be very careful around any

oxalate. Wear nitrile gloves, a dual-filter respirator,

and safety glasses. Also, never work with any oxa-

late without adequate ventilation. Do not breath

the fumes of any oxalate because its fumes can be

absorbed through the lungs. If you spill an oxa-

late on your clothing, forget modesty; remove your

clothing and wash well with plenty of water. Do not

mix any oxalate with a strong concentrated acid or

oxidizer, and do not dispose of it in any place but a

hazardous waste facility. Most college photography

labs have contracts with chemical disposal services,

and you should contact them for assistance if you

need to get rid of dangerous chemistry.

Ammonium Hydroxide (30% Ammonia)CAS#1336-21-6

This chemical, also known as ammonia water, is

often found in developing and toning solutions as

an accelerator. Essentially, it is an aggressive form

of ammonia and water used in the mordançage pro-

cess. A 5% solution is the equivalent of household

ammonia. Always work with good ventilation and

wear gloves.

Ammonium Thiocyanate CAS # 1762-95-4

Also known as ammonium sulphocyanide,

ammonium thiocyanate is a component of gold-thio-

cyanate toning in PoP and appears as a colorless, del-

iquescent (readily absorbs water) crystal with a slight

odor of ammonia. It is incompatible with chlorates,

oxidizing agents, peroxides, and strong acids, with

which contact will liberate a toxic hydrogen cyanide.

Inhalation will cause respiratory distress, and all nor-

mal safety precautions should be adhered to when

using the chemical.

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Ammonium Thiosulphate (Rapid Fixer)CAS# 1183-18-8

This chemical, when substituted for sodium thiosulphate,

is used as a fixing salt in many high-speed fixers (e.g.,

rapid fixer). In terms of fixing speed, it is much faster

than sodium thiosulphate. It can be used easily as a fixer

in the wet plate collodion process and is preferred if you

are anxious about working with potassium cyanide as

your fixer. It will take a few additional minutes to fix your

plate versus using KCN, and the wash time is significantly

longer for the plates, but it is safer. Ammonium thiosul-

phate is a colorless crystalline salt with strong fixer-like

odor. Extended contact, as all photographers know, will

cause skin irritations. Decomposition or heating of this

chemical will release a highly toxic sulphur dioxide gas.

Keep it away from cyanotype chemistry. use tongs when

working with this chemical, and wear gloves and a respi-

rator when mixing.

Borax (Sodium Tetraborate) CAS# 1303-96-4

This is powdered laundry soap. Employed as a laun-

dering agent, borax is the same chemical you will find

in the supermarket. It is often used as a weak alkali

accelerator in developers and in some hardening fixing

baths. It is also used to make a gold toner more alka-

line and allows for a faster rate of gold deposit. Its use

has a moderate health risk, and normal safety precau-

tions should be adhered to when using it. If you ingest

or breathe large quantities of it, wash the exposed area

well and seek medical attention if symptoms persist

(e.g., difficulty breathing, irritation, muscular spasms,

itching, or pain).

Boric Acid CAS# 10043-35-3

This chemical is used in hardening fixers contain-

ing potash alum and acetic acid. It extends the life of

fixers and can be found in some buffered fine-grain

developers.

Cesium Chloropalladite

Cesium is a double salt built on an alkaline metal

compound. It sits at the lower end of Group 1 on the

periodic table and is a very heavy metal used in the

Ziatype process (for the brown coloration). This chem-

ical, found in certain non-silver processes, is an irritant

to the skin, eyes, and respiratory system. Seek medical

attention if physical distress accompanies its use.

Chrome Alum (Potassium Sulphate) CAS# 7778-99-0

Chrome alum appears as a deep red/purple granule and

has no odor. It is sometimes employed as a hardening

agent for gelatin and has a moderate health risk asso-

ciated with its use. It is incompatible with aluminum

and magnesium and will cause respiratory distress if

inhaled. Do not touch your skin, eyes, or mucous mem-

branes while using it, and flush any infected area with

copious amounts of water. Seek medical attention if

symptoms persist.

Citric Acid (2-hydroxypropane) CAS# 77-92-9

Since we use a great deal of this chemical in alternative

process work I have a little more to say about it than

others. Citric acid is very useful as a first rinse bath

in iron processes in that it lessens the chance of your

print developing iron stains. EDTA performs a simi-

lar chore as a chelate. Citric acid is the most common

food acidulant, an acid combined with a food product

to flavor or preserve. It is abundant in unhealthy snack

foods. This acid was initially extracted from lemons or

other citrus fruit, but today it is manufactured through

a sucrose fermentation technique and is recovered

by precipitation, evaporation, or crystallization. It is

available in two forms—monohydrate or anhydrous

(approximately 8.6% moisture)—and is sometimes

available as a solution. The product obtained by fer-

mentation is identical to organic citric acid.

We work with citric acid in a white powder form,

and it is colorless upon dilution. It is also odorless with

a strong acidic flavor. one gram is soluble in 0.5 ml

water. The pH of a 1% solution of the monohydrate is

2.3, and the pH of a 1% solution of the anhydrous form

is 2.2. The food and Drug Administration recognizes

citric acid as safe.

Citric acid aids in the preservation of texture, color,

aroma, and vitamin content of food products and is

particularly useful as a chelant. It is the preferred

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acidulant to ensure optimum gel formation in pectin

products. This chemical is commonly used in ton-

ers, as a clearing bath for some alternative processes,

and it is one of the alternatives to hydrochloric acid in

platinum/palladium clearing. Citric acid is also used to

transfer photomechanical ink images, (Rauschenberg

used it) via saturation and rubbing the image on a

clean piece of paper from the rear of the saturated

paper. It is not dangerous to work with but can cause

irritations to eyes, skin, and the respiratory system if

handled in a cavalier manner. However, do not mix cit-

ric acid with metallic nitrates because the reaction may

be explosive. It is also incompatible with carbonates,

copper, aluminum, and zinc.

Collodion USP CAS# 99994-22-6

Collodion is a viscous fluid that is used in photographic

practice as a salted binder for sensitizing wet plate,

ferrotype, and ambrotype glass plates. It is not

particularly dangerous but is very flammable, and

precautions should be made when working with the

material. Although it is possible to make collodion

at home with nitrated cotton, ether, and alcohol,

I strongly advise that you do not do so. Instead,

purchase a prepared plain collodion.

When using collodion be sure to have adequate

ventilation, wear gloves, and wear a respirator if

airborne concentrations are high. Collodion vapors can

exist quite a distance from the actual material, and you

must be sure that any ignition source is off before use.

Keep the collodion away from strong acids and oxidizers

and take general lab safety precautions when using it.

When you wish to dispose of unused collodion,

spread some newspapers outside in a non-windy

place (I use a wheelbarrow in the garage) and pour

out thin layers of the collodion on the newspaper. It

dries quickly as a thin skin. Repeat the step until your

collodion is gone and then clean your container with

Everclear alcohol (190 proof). Do not use the newspa-

per to start a campfire, as it will be explosive.

Copper Chloride CAS # 10125-13-0

Copper chloride appears as a blue/green crystal and

is used in many toners, bleaches (mordançage), and

intensifiers. This chemical is a strong oxidizing agent

and presents a significant health hazard if used casu-

ally. Avoid light, air, and moisture in storage. Toxic

fumes are harmful if breathed, and its dust must be

avoided. Always wear a dual-filter respirator, gloves,

and goggles when mixing or using. Copper chloride

is incompatible with potassium, sodium, oxidizers,

and strong acids that may result in the release of toxic

chloride vapors. overexposure will result in a host of

problems, including respiratory distress, chills, burn-

ing sensations in the intestinal tract, headache, and so

on. Be very careful when using this chemical, and seek

immediate medical attention if in distress.

Copper Nitrate CAS# 10402-29-6

Be careful around this chemical because it is harmful

to your body. Prolonged or intense contact will cause

chills, gastrointestinal problems, and pain. Avoid con-

tact with the skin, breathing, or ingestion. Irritations

of many sorts, and burns, are common if precaution is

not taken in the use of this chemical. like all nitrates,

you must be vigilant when using it and adhere to all

safety precautions: gloves, goggles, and a respirator.

Seek immediate medical attention if in distress.

Copper Sulphate CAS# 7758-98-7

Copper sulphate appears as a blue/translucent crystal

or powder. This chemical is used in toners (copper),

bleaches, and intensifiers. Not a great deal is known

about this chemical other than it is a moderately toxic

one and all precautions should be taken in its use

and handling. Wear gloves and a respirator for mix-

ing or prolonged use, and do not touch your eyes or

mouth when using it. Copper sulphate is an irritant.

The usual routes by which humans can receive toxic

exposure to copper sulphate are through eye or skin

contact, as well as by inhaling powders and dusts. Skin

contact may result in itching or eczema. Eye contact

with copper sulphate can cause conjunctivitis, inflam-mation of the eyelid lining, ulceration, and clouding

of the cornea. upon oral exposure, copper sulphate is

only moderately toxic. According to studies, the low-

est dose of copper sulphate that had a toxic impact on

humans was 11 mg/kg. Because of its irritating effect

on the gastrointestinal tract, vomiting is automatically

triggered upon ingestion of copper sulphate.

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Copper(II) sulphate, also known as cupric sulphate

or copper sulphate, is a chemical compound with the

chemical formula CuSo4. This salt exists as a series

of compounds that differ in their degree of hydra-

tion. The anhydrous form is a pale green or gray-white

powder, whereas the pentahydrate (CuSo4·5H2o),

the most commonly encountered salt, is bright blue.

CuSo4·5H2o is a shade of blue and is very toxic to

the environment and is irritating to the eyes and

skin. It can be harmful if swallowed. other names for

copper(II) sulphate are “blue vitriol” and “bluestone.”

Copper sulphate is a commonly included chemical

in children’s chemistry sets and is often used to grow

crystals in schools and in copper plating experiments.

Copper sulphate is also used to test blood for anemia.

for most of the twentieth century, chromated cop-

per arsenate (CCA) was the dominant type of wood

preservation for uses other than deep driven piles, util-

ity poles, and railroad ties. It gives the treated wood

a peculiar green coloration. To make pressure-treated

wood, a large cylinder is filled with an aqueous chemi-

cal bath. Copper sulphate pentahydrate is dissolved in

the water along with other additives prior to the lum-

ber being placed inside the cylinder. When the cylin-

der is pressurized, the chemicals are absorbed by the

wood, giving the wood fungicidal, insecticidal, and

uV-light-reflecting properties that help preserve it.

EDTA

Disodium EDTA (Disodium Salt Dihydrate) CAS# 6381-92-6

Also known as ethylenediamine tetraacetic acid and

disodium salt. It is used as a first clearing bath for Pt/

Pd. It may irritate the skin, eyes, and respiratory sys-

tem. This chemical is more of an irritant than a danger

and should be handled in a similar manner as its sibling,

tetrasodium EDTA.

Tetrasodium EDTA (Tetrasodium Salt Dihydrate) CAS# 10378-23-1

Repeat after me . . . ethylenediamine tetraacetic acid

tetrasodium salt dihydrate is a chemical recently

employed as an alternative to hydrochloric or citric

acid in some clearing baths. It is relatively safe to use

and is commonly found as a preservative in some foods

and in agricultural uses. It may irritate the skin, eyes,

and respiratory system. EDTA is generally purchased

in a white crystal form and can cause minor problems

if you are too casual when using it.

EDTA is commonly found as a preservative in pro-

cessed foods, in cosmetics to improve stability, as a

detergent in the dairy industry to clean bottles, as a

treatment for mercury poisoning, and in soft drinks

containing ascorbic acid and sodium benzoate (most

all of them) to reduce the formation of the carcinogenic

benzene. It can also be used in the recovery of used lead

acid batteries and is found in cleaning compounds,

detergents, and in photography as an oxidizing agent.

Ferric Ammonium Citrate CAS# 1185-57-5

ferric ammonium citrate is also known as iron

ammonium citrate, ammonium ferric citrate, iron

citrate, and ammonium iron (III) citrate. It presents

itself as a green, or brown, scale crystal/powder, has

a somewhat undetermined structure, and is prepared

by treating ferric hydroxide with hydrated citric acid

(75%), iron (16%), and ammonia (7.5%). This chemi-

cal is commonly found in human-ingested iron sup-

plements, cyanotype formulas, iron toners, and other

non-silver formulas, and it functions as a sensitizer. It

is not particularly toxic, but you must still exercise care

in its handling, storage, and use. It may be the cause

of eye and skin irritations if precautions are ignored.

If you notice that your urine is pink, then you have

absorbed or inhaled far too much of this stuff and you

should seek medical attention.

Ferric Citrate CAS # 2338-05-8

ferric citrate is a brownish red powder in a 17% iron

state. There is a purified variation of this chemical, but

it is not what you are looking for in alt pro work. ferric

citrate is light sensitive and is used, for our purposes,

primarily as an ingredient in preparing a Van Dyke Part

C contrast control alternative to be mixed with the tradi-

tional Van Dyke Part C. See the Van Dyke chapter. It is

not particularly toxic, but you must still exercise care in

its handling, storage, and use. It may be the cause of eye

and skin irritations if precautions are ignored.

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Ferric Oxalate (Ferric Ammonium Oxalate) CAS # 2944-67-4

Platinum and kallitype printers use ferric oxalate as

the light-sensitive ingredient in their sensitizers. It is

an oxalic acid salt and is toxic. The body can deal with

it in small quantities. ferric oxalate is a weakly bound

chemical and will quickly decay to ferrous oxalate and

then to oxalic acid and ferric oxide (rust). Please see

the potassium oxalate entry for more information.

ferric oxalate is a green/transparent crystal and is

light sensitive. All oxalates are toxic, and you should avoid

breathing, touching, or ingesting them. They are corro-

sive to all parts of your body and can cause ulcerations

on the skin. Severe kidney damage can be the result of

large amounts of absorption or breathing fumes. Wear

latex or nitrile gloves, a respirator, and eye protection

when working with oxalates. If you happen to spill ferric

oxalate on your skin, wash it well with clean water. If you

spill it on your clothing, remove that clothing and wash

it well. If it is ingested, call a doctor and poison control.

Be extra cautious when using any oxalate because it is a

most serious health hazard if used in a casual manner.

EDTA is a chelate that will dissolve ferric oxalate . . .

an important thing to know when you need to use it as

a clearing bath.

Ferrous Sulphate CAS# 7782-63-0

This chemical is used in standard wet plate collodion

developers. It is also used in stain removing and

clearing baths. If you have taken in too much of this

chemical through breathing, touching, or tasting, you

will have an acidic and sour taste in your mouth. It

does not keep well in solution. This chemical can cause

itching, burning in the eyes, breathing difficulty, and

general ill health. Be diligent in its use and follow all

safety precautions. Seek immediate medical atten-

tion if you find yourself in discomfort or distress when

using this chemical.

Formalin/Formaldehyde CAS# 50-00-0

formalin/formaldehyde, a 37% concentration of

formaldehyde gas in water with an additional com-

ponent of methyl alcohol, is employed as a hardener

and preservative in photography. formalin is used

as a tanning and hardening agent of gelatin in gum

bichromate and other processes in which sizing/

hardening is required. This chemical is highly toxic

and unhealthy to the body if safety precautions are

not used. Do not breathe the fumes (which are very

strong) and work only in very well-ventilated envi-

ronments, such as outdoors with the wind at your

back. Be cautious of formalin-prepared papers

indoors, after they are dry, because they will con-

tinue to outgas for a day or so and be dangerous to

your respiratory system. fumes from formalin will

attack the mucous membranes of your eyes, nose,

and throat. This chemical is a carcinogen and you

must take it very seriously. If somehow this chemical

is ingested, seek immediate medical attention: you

will see the following . . . coughing and respiratory

distress that persists, violent vomiting, headache,

severe abdominal pain, weak pulse, burns, blurred

vision, and sudden change in skin color to white. In

other words, take this seriously.

See glyoxal below.

Fumed Silica

fumed silica (not to be confused with silica fume)

is amorphous (meaning it has undefined shape and

form), rather than crystalline, and is a vaporized form

of clear solid silica that behaves as if it were a liquid.

fumed silica is made by flame hydrolysis of silicon

tetrachloride. Silicon tetrachloride is a liquid at room

temperature. It is vaporized and then passed through

a fuel/air flame at an extreme temperature to pro-

duce fumed silica. fumed silica is essentially a harm-

less, non-carcinogen that is a primary thickening

ingredient in fast-food milkshakes and is used as an

anti-caking agent in powders, an abrasion resister in

concrete, and in kitty litter. It also features light-dif-

fusing properties, which is one of the reasons the dark

end of the tonal scale looks so nice in an alt pro print

that employs it as a pre-coating. It is also found in

cosmetics like lipstick and toothpaste. When applying

it with a hot-dog roller as a pre-coating to a process

on paper, it would be prudent to wear eye protection

and a respirator.

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Gallic Acid CAS # 149-91-7

Gallic acid appears as a white/pale yellow crystal and is

used as a component in cyanotype toning and as a tradi-

tional chemical in calotype development and developing-

out formulas for processes such as the whey technique. It

does not present a significant health hazard but is incom-

patible with ferric salts, silver salts, alkalis, ammonia,

chlorates, and strong oxidizing agents. overexposure will

cause moderate discomfort and should be treated with

respect regardless of its low toxicity.

Glyoxal CAS# 107-22-2

This chemical is recommended as a substitute for

formalin/formaldehyde as a hardening agent for

gelatin in sizing for the gum bichromate process. It

is an alternative, in terms of reactivity and toxicity, to

formalin, but insufficient evidence has been offered

by the scientific community to allow you to treat it

casually. Glyoxal should never be mixed with sodium

hydroxide or nitric acid, and if heated in an enclosed

container, it is explosive. It is also corrosive to all

metals. Glyoxal should be used in well-ventilated

environments (such as outdoors), and all precau-

tions should be taken to prevent ingestion, contact

with the skin, and breathing of its fumes. Note: Just

because glyoxal doesn’t have an offensive odor like

formaldehyde, doesn’t indicate that it is safer and

that you can relax using it. Treat glyoxal with the

same respect you would formalin. After sizing your

gum paper with gelatin and glyoxal, hang it to dry in

well-ventilated space outside of your living area. It

requires an off-gas period of 24 hours. once dried,

label each sheet as glyoxal sized and store the sized

paper in a zip lock bag.

Gold Chloride CAS# 16903-35-8

Gold chloride is also known as chloroauric acid,

gold trichloride acid, and hydrogen tetrachloroau-

rate (III). Gold chloride is generally used in dilu-

tions of 1%, 5%, and 8% for purposes of toning in

a number of processes. Gold chloride is also a pri-

mary component in Ziatype printing and will raise

the contrast of the print when added to the formula.

Gold chloride is a strong irritant and can cause

significant skin and respiratory allergies if you are

casual with it. Pay heed to all normal precautions

when using this chemical.

Gum Arabic CAS# 9000-01-5

Gum arabic, or gum acacia, can be traced back to 2650

BCE, when it was harvested from the sap of various

species of acacia trees in Nigeria, Cameroon, Chad,

Mali, and the Sudan. The acacia trees grow primar-

ily in the sub-Saharan (Sahel) areas of Africa, and the

Sudanese variety is considered the premium grade.

In gum printing, the dichromate is added to the gum

to create the liquid foundation of the gum sensitizer.

Gum arabic comes in a variety of grades (tints) from

colorless to dark brown. on exposure to light, the gum

and the ammonium dichromate solution will harden in

proportion to the exposure of uV light.

Hydrogen Peroxide (3%) CAS# 7722-84-1

Hydrogen peroxide is a colorless and not very stable

liquid used primarily as a bleaching agent, an antiseptic,

or an oxidizing accelerator in the cyanotype process.

You do not have to be enormously concerned with this

chemical when purchased in its 3% over-the-counter

form. In dentistry applications it is often mixed with

water and used to clean wounds inside the mouth.

In this concentration, which we are most accustomed

to as a treatment for cuts and abrasions, hydrogen per-

oxide is a simple peroxide and an oxidizer . . . which is

what is happening when you pour it on an active wound

and it generates a white effervescent foam. Hydrogen

peroxide is used in alternative processes as an oxidizer

for the iron in cyanotypes (the WoW factor effect) when

prepared in a very dilute bath for a finished cyanotype,

resulting in a very deep and beautiful blue.

Hydrogen peroxide is also used to neutralize potas-

sium cyanide (KCN) wet collodion fixer by converting

it to a safe, and unregulated, potassium cyanate. See

the instructions in the Wet Collodion chapter.

Hydrogen Peroxide (28%–33%)

In this strong concentration, hydrogen peroxide

is used primarily for mordançage bleaching and

in beauty parlors to alter hair color. It is a health

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hazard. Wear appropriate protection, do not breathe

the fumes, and flush exposed areas well with water

if you experience problems after contact. If you work

in a beauty salon, please wear appropriate protec-

tive clothing, gloves, and breathing apparatus . . . this

stuff is not good for you and may, under some cir-

cumstances, lead to pulmonary edema . . . also known

as high-altitude sickness, in which fluid accumulates

in the lungs.

Hydrogen Tetrachloroaurate(III) Trihydrate CAS# 27988-77-8

used in the sensitizer for chrysotype—version S.

Also known as gold(III) chloride hydrate and hydo-

chloroauric acid. In early literature it was called

gold chloride. This chemical is corrosive and can

be destructive to your mucous membranes. Take

appropriate safety and working measures when

using it.

Kodak Hypo Clearing Bath

This solution is used to accelerate the neutralization

of fixer and therefore cut the wash times for films and

papers. Two formulas for hypo clearing baths are the

following.

formula #1: 750 ml water, 200 g sodium sulphite

(anhydrous), 50 g sodium bisulphite, and water to

make 1 liter.

formula #2: 125 ml hydrogen peroxide, 10 ml

ammonia solution, and water to make 1 liter.

other formulas include sodium sulphite, EDTA,

sodium citrate, and sodium metabisulphite. Hypo

clearing agents can be mild irritants to the body in

concentrated solutions for lengthy exposure.

Lead Acetate CAS# 301-04-2

This chemical is used as a toner. lead acetate is a

possible carcinogen, and like other lead products,

is toxic. It can be a problem for your body and can

be absorbed by breathing its fumes. It is a poison

if ingested and can cause brain damage. fumes are

released when it is heated. Be cautious in all safety

respects when using this chemical.

Lithium Palladium Chloride/Lithium Chloropalladite

lithium palladium chloride/lithium chloropalladite

is a double salt built on an alkaline metal compound

(lithium), which is a lightweight alkali sitting atop the

periodic table. It is used in the Ziatype process and

results in a cool black value. Do not drink it or play

with it. lithium is a primary component in medicating

bipolar disorder, and high incidences of exposure can

have adverse effects on the nervous system.

Mercuric Chloride CAS# 7487-94-7

Also known as mercury(II) chloride, mercuric chloride

was used as a photographic intensifier to produce

positive pictures in the collodion process of the 1800s.

When applied to a negative, the mercury(II) chloride

whitens and thickens the image, thereby increasing the

opacity of the shadows and creating the illusion of a

positive image (Towler, 1864).

Mercuric chloride is toxic, white, and a soluble salt

of mercury (at 6%). It has been used in disinfectants,

as a fungicide, as a treatment for syphilis before antibi-

otics, and in photographic fixers. It’s also odorless and

really dangerous, which is why I’m letting you know

about it here. Take all safety precautions when work-

ing with this chemical.

Methyl Alcohol (Wood Spirit) CAS# 67-56-1

This is a poison. It can be readily absorbed by breathing

and through the skin and is considered very dangerous to

the central nervous system. It can cause blindness. use all

safety precautions against exposure when using methyl

alcohol. If methyl alcohol is swallowed, administer an

emetic (a medicine that induces vomiting) and bicarbon-

ate of soda (1 tsp in a cup of water), and call a doctor.

Muriatic Acid (Hydrochloric Acid) CAS # 7647-01-0

Muriatic, or hydrochloric, acid is a clear, colorless,

irritating, vaporous poison that was used as a primary

clearing bath with Pt/Pd and as a tray cleaner . . .

among other uses. It can be purchased at hardware

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stores and pool supplies and is often used by masons

for cleaning bricks. Be respectful of this chemical and

take precautions while using it.

Nitric Acid CAS# 7679-37-2

Nitric acid is a colorless liquid and will make its appear-

ance known as soon as you unscrew the top to its bot-

tle; a chemical vaporous smoke will appear like an evil

genie from the bottle. It is used in some cyanotype ton-

ing formulas, as a preservative in Pyro developers, and

as a component in bleach. Nitric acid is highly corro-

sive to most anything it comes in contact with, includ-

ing your body. At present, there is really no safe way

to use this chemical in regard to ventilation except for

with a professional chemical hood. Nitric acid is a very

aggressive oxidizer and will react violently with a vast

range of metals, acids, solvents, and other things found

in the lab or home. Although I like using it in cyano-

type toning I am not sure if the resulting color is actu-

ally worth the risk. If you are a teacher, you mix the

formula. Also, be careful of the cap on the glass bottle

that the acid is stored in. If it is an old fashioned plastic

cap there is a good chance that the acid will destroy

the cap’s integrity in time. Be hyper-careful in its use

and storage. If this chemical is spilled on skin, wipe

off what you can, immerse the relevant skin areas in

water, and then cover the area with a paste of water

and baking soda. Go to a hospital and seek immedi-

ate medical attention. If you spill it on your clothing,

forget modesty and immediately remove your clothes.

If nitric acid is ever swallowed, administer a small

amount of soap softened in water, milk, or raw egg.

You can also force the patient to drink a small amount

of magnesia or plaster softened in water. Seek medical

assistance for extreme exposure.

Oxalic Acid (Ethanedioic Acid) CAS# 144-62-7

oxalic acid is translucent and odorless. This chemical is

used in blue toners and as a preservative in certain Pyro

formulas. It is found in all leafy green vegetables but is

highly toxic in strong concentrations so you must use all

safety precautions in its use and storage. oxalic acid is

corrosive to tissue and removes calcium from the blood,

which may result in kidney damage. It is incompatible

with alkalis, silver, and oxidizing agents. Take normal

safety precautions when using this chemical.

Take all necessary precautions when using oxalic

acid because it is toxic. Its primary role in your life

is likely to be as a cleaning and bleaching agent . . .

especially for the removal of rust/iron deposits. In

alternative processes, oxalic acid is also used as a

reducing agent in the platinum/palladium process.

The principle toxicity risk when using oxalic acid is

due to kidney failure, which may cause precipitation

of solid calcium oxalate, the main ingredient of kidney

stones. That said, wear nitrile or safety examination

gloves and eyewear when using this chemical.

Palladium Chloride CAS# 7647-10-1

Palladium chloride is dark brown and without odor.

This chemical is found primarily in palladium printing

and in certain other non-silver processes and is an

irritant to the skin, eyes, and respiratory system.

Palladium chloride is moderately toxic. It is often asso-

ciated with bipolar disorder medication. High doses

can cause problems with central nervous system func-

tions. Be cautious of contact with the skin, ingestion,

and breathing fumes. use normal precautions in its

use and handling.

Potassium Bromide CAS# 7758-02-3

Potassium bromide appears as white crystal and

is without odor. This chemical is often used as a

restrainer in bleachers and developers. It is also widely

used in intensification, reducing, toning, and many

other photographic formulas. It is mildly irritating

to the tissues of your body and can sometimes cause

skin problems. It is a mutagen, and extreme exposures

can result in depression of the central nervous system.

Potassium bromide is incompatible with strong oxidiz-

ers and acids. use all safety precautions.

Potassium Chloroplatinite CAS# 10025-99-7

This chemical is found in toners and intensifiers, and

it is the primary ingredient in platinum printing. It

is highly corrosive to human tissue and can cause

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severely adverse reactions to extreme or long-term

exposure. This chemical is a poison and should be used

and handled with all safety precautions.

Potassium Cyanide CAS# 151-50-8

Potassium cyanide (KCN) is a white granular,

odorless crystal, much like sugar, and is also

known as hydro/potassium salt of hydrocyanic

acid. Highly toxic, a health hazard, and level III,

KCN is odorless, but due to hydrolysis, solids emit

small amounts of hydrogen cyanide, which smells

like bitter almonds. KCN is highly soluble in water

and is actively employed in, as well as a preferred

chemical for, fixing wet plate collodion due to its

ability to lend brightness to the plates, longevity,

and coffee and cream highlight coloration in tin-

types and ambrotypes and because washing times

for the plates are measured in seconds rather than

minutes . . . which is useful if making plates on a

battlefield or if you are backpacking and can’t take

along a lot of water. KCN is extremely dangerous

and must never be placed in a situation where it can

come into contact with an acid . . . thus creating a

lethal hydrogen cyanide gas.

Exposure to potassium cyanide can be rapidly

fatal. It has whole-body (systemic) effects, particularly

affecting those organ systems most sensitive to low

oxygen levels: the central nervous system (brain), the

cardiovascular system (heart and blood vessels), and

the pulmonary system (lungs).

X Note: To neutralize a 1.2% potassium

cyanide fixer solution (standard dilution for

wet plate collodion), put on eye protection, a

respirator, and nitrile gloves and place potas-

sium cyanide in an empty and clean drywall

bucket or large glass beaker. Slowly add 600 ml

of drugstore-grade 3% hydrogen peroxide to a

liter of used potassium cyanide. In a short time

you will have converted a heavily regulated

chemical to a non-hazardous, un-regulated

potassium cyanate.

Please read the section on potassium cyanide in the

fixing section in the Wet Plate Collodion chapter.

Potassium Dichromate CAS# 7778-50-9

Potassium dichromate (bichromate) is a beautiful

orange crystal that is used as a principal sensitizer

in the gum bichromate processes and as a contrast

boost additive in many non-silver processes. It is also

a bleaching agent. It is most often used as a saturated

solution or diluted for use as a contrast additive to

wash-development baths or sensitizer. It is highly

toxic, corrosive, and can enter the body through

absorption, ingestion, and breathing. It can cause

extreme allergic reactions and is a powerful irritant

to human tissues and internal systems. It is a carcino-

gen and must be handled with care. It is incompatible

with any combustible, organic, or oxidizable mate-

rial. It is extremely destructive to tissue and respira-

tory systems and may cause distress. If this chemical

is spilled on clothing, remove the clothing immedi-

ately. Do not be the least bit casual when using this

chemical, and seek immediate medical attention if

you experience discomfort in breathing, burning, or

dizziness.

(See Ammonium Dichromate for safety and

disposal.)

Potassium Ferricyanide CAS# 13746-66-2

Potassium ferricyanide is an orange-red crystal and

has no odor. It is also called red prussiate of potash

and is used in reducers, bleaches, toners, and many

alternative and non-silver processes, specifically

iron based. Ruby red in color, potassium ferricya-

nide is a low- toxicity-level chemical. It is the Part A

(bleaching agent) of sepia toner and is one of the

primary ingredients in cyanotype. Potassium ferri-

cyanide is poisonous in high concentrations. Take

all necessary precautions in its use and handling.

Do not expose it to acids, because it may release a

cyanide gas (hydrocyanic acid). If potassium ferri-

cyanide is swallowed, administer a tablespoon of 3%

hydrogen peroxide. Have the patient inhale ammo-

nia fumes, provide artificial respiration if necessary,

and call a doctor. Potassium ferricyanide is incom-

patible with extreme heat and can release fumes of

cyanide and oxides of nitrogen. It is also incompat-

ible with ammonia. use standard safety precautions

when using this chemical.

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Potassium Iodide CAS# 7681-11-0

Potassium iodide, also known as potassium salt, is

a white, odorless chemical used as a salting agent in

the first stage of the calotype and is responsible, in

combination with silver nitrate, for the silver iodide

compound. It is not a particularly hazardous chemical,

but you should take normal safety precautions when

using it. Avoid breathing, ingesting, or placing potas-

sium iodide in direct contact with your skin. If you get

any in your eyes or on your skin, flush the area with

clean water for 15 minutes. Seek medical attention if

irritation or a rash persists.

Potassium Metabisulphite CAS# 16731-55-8

Potassium Metabisulphite is a white crystalline

powder with a pungent sulphur odor. The main use of

the chemical is as an antioxidant or chemical sterilant.

It is a sulphite and is chemically very similar to sodium

Metabisulphite, with which it is sometimes used

interchangeably. Potassium Metabisulphite is used as

a clearing agent in the gum bichromate process.

Potassium Oxalate CAS# 583-52-8

The oxalates are the only salts that are poisonous, but

they are not always bad for you or the environment.

oxalic acid is commonly found in nature (e.g., in green

leafy vegetables) and is responsible for the bitter taste.

Too much of it is not good for you . . . 10 pounds of spin-

ach in one sitting is a lethal dose of oxalic acid. In small

quantities the human body deals with the oxalates quite

handily, as the body produces natural chelates that ren-

der them harmless. The most commonly used developers

such as ammonium citrate, potassium oxalate, sodium

acetate, and sodium citrate are quite harmless and can be

disposed of in a municipal sewage system if well diluted.

Potassium oxalate is transparent and odorless, and

it is used in toners and as one of the developer options

for platinum/palladium. like all oxalates, this chemical

in a concentrated form is toxic and corrosive to human

tissue. unsafe exposure is foolhardy because this chemi-

cal can cause significant problems for all parts of your

body. It is incompatible with strong acids and oxidiz-

ers. use all safety precautions, including nitrile gloves,

a respirator, and safety glasses. Seek immediate medical

attention if you experience distress when using it. Signs

and symptoms of distress are nervousness, cramps,

depression, corrosive action on the mucous membranes,

redness of the skin, blurred vision, burns, and pain.

Potassium Sodium Tartrate (Rochelle Salt) CAS# 304-59-6

Potassium sodium tartrate is a double salt first

prepared in la Rochelle, france, in 1675. As a result the

salt is known as Rochelle salt and is used in alternative

processes in the kallitype. Rochelle salt can be made

from common household goods: cream of tartar and

baking powder.

Pyrogallic Acid CAS# 87-66-1

This chemical is principally used as a high-octane

developer for pyromaniacs. It is a chemical used in

many alternative developers such as calotypes and

for processing film-based negatives for processes

such as Pt/Pd due to the tan coloration it gives the

film stock during development. It enters the body

through absorption. It may cause respiratory and

gastrointestinal problems. Avoid the chemical’s dust

or breathing its fumes. use appropriate safety pre-

cautions.

Silver Nitrate CAS# 7161-88-8

Silver nitrate appears as a colorless and odorless

crystal and discolors on exposure to light. Silver nitrate

is highly corrosive. This chemical can cause severe skin

and eye problems and is particularly destructive to

mucous membranes and the upper respiratory tract. It

is the primary silver salt found in photographic emul-

sions, alternative processes (e.g., Van Dyke, salted

paper, kallitype, albumen, calotype, etc.), and intensi-

fiers. Silver nitrate will discolor your skin, is a caustic

substance, and may cause blindness if it gets into your

eyes. If you get silver nitrate on your skin, you may

experience redness and an eventual henna-like brown

stain that will last for several days. on exposure, wash

the area well with repeated rinses of water. Rubbing

the area of exposure with sodium chloride (table salt)

will help lessen the damage to a degree and will help

with stain removal.

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This is more serious . . . if you get silver nitrate in

your eyes, immediately flush with copious amounts

of water, or saline solution, and continue doing so

while medical attention is summoned. If you get a

bad silver nitrate stain on anything but your eyes,

you can eliminate the black stain by washing the

area with a solution of 2 teaspoons of sodium bisul-

phite in a quart of water. Be cautious of the sulphur

dioxide gas that will be created by this act of cleans-

ing. If you happen to ingest silver nitrate you will

experience great distress, burning, shock, and coma.

Do not induce vomiting. force feed strong salted

water concentrations.

Silver nitrate is a very strong oxidizer. It will combust

and explode if allowed to come into contact with any

ammonia compounds, such as ammonium hydroxide

(the strong concentration of ammonia used in mordan-

çage). Never mix silver nitrate solutions with metals such

as aluminum or zinc. use extreme safety precautions

especially by wearing gloves, a respirator, and goggles or

safety glasses when working with this chemical.

Sodium Acetate CAS# 127-09-3

Sodium acetate is the sodium salt of acetic acid. Its pH

rests between 7.5 and 9.5. It is an inexpensive chemical

produced in industrial quantities for a wide range of

uses. As the conjugate base of acetic acid, it is a rel-

atively strong base. Sodium acetate is used as one of

several developer options for platinum/palladium and

is not particularly toxic. Sodium acetate is often found

in toners such as gold and is employed as a buffer in

acidic solutions. It should be used and handled with

respect. use normal safety precautions.

Sodium Bisulphate CAS# 7681-38-1

Sodium bisulphate appears as a white crystal and is odor-

less. It is used as an acid rinse and in combination with

acetic acid, as a stop bath. It can also be used in conjunc-

tion with sodium chloride to make a hydrochloric acid

substitute. It presents a low health risk, but normal safety

precautions should be adhered to when using it.

Sodium Bisulphite CAS# 7631-90-5

Sodium bisulphite is a coarse, white granule and has

a strong odor of sulphur. It is used as a preservative

in fixing baths and for removing stains from gum

bichromate and PoP processes. It can be substituted

for sodium Metabisulphite. It is a strong irritant to the

respiratory system and can cause irritation to the skin,

eyes, and mucous tissue. Take normal safety precau-

tions when using this chemical.

Sodium Carbonate (Anhydrous) CAS# 497-19-8

Sodium carbonate appears as a white, odorless

granule. This chemical is also called soda ash and

hydro-sodium and is used as a primary alkali accelera-

tor in developers. It is also used in cyanotype toning

and works as a reducer and bleach on iron prints. It is

an irritant to eyes, tissue, and the respiratory system.

Sodium carbonate can release a gas when mixed with

acid, stop, or fixing baths. It reacts violently with acids,

and caution should be taken. Kodak Balanced Alkali

(Kodalk) can be used as a replacement for sodium

carbonate. use with care regardless of the low risk.

Sodium Chloride (Kosher Salt) CAS # 7647-14-5

Sodium chloride appears as a white, odorless crys-

tal and has a very low health risk associated with it.

It is primarily used in salting gelatin for albumen and

salted paper printing, as a fixing agent, as an additive

to first rinse washes, and, when mixed with water, as

a wonderful substance to go scuba diving in. It is also

good to keep on hand in the lab for when you order

out for pizza. Note: Do not buy ordinary table salt and

think that it is pure sodium chloride. More than likely

it is loaded with additives. Buy kosher salt or sodium

chloride from a chemical supply. use caution not to

rub it in your eyes, and flush overexposed areas with

water to rinse them clean.

Sodium Citrate (Tri-Sodium Citrate) CAS# 68-04-2

Add baking soda to citric acid and you’ll get sodium

citrate. Sodium citrate appears as a fine, white, odorless

granule and is incompatible with strong oxidizers. A

common use of this chemical is as a primary ingredient

in salted paper gelatin salted emulsion and kallitype

developer. This chemical has a low health risk but can

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cause mild irritations to the eyes, tissues, and respira-

tory system. Sodium citrate is used in ice cream to keep

the fat globules from sticking together and as a buffer-

ing agent. Sodium citrate attaches to calcium ions in

water. Compounds with similar functions are sodium

carbonate, EDTA, and phosphoric acid.

Sodium Gold Chloride CAS# 13874-02-7

Sodium Palladium Chloride (see Potassium

Chloroplatinite)

This chemical can cause severe allergic reactions

and is an irritant to human tissue. Do not allow it to get

into contact with your skin, and do not ingest or breathe

its fumes. use proper safety precautions at all times.

Sodium Potassium Tartrate CAS# 304-59-6

Also known as rochelle salt. It is used in some toners

and sensitizers and as a developing component in

kallitype. There are no health hazards associated with

this chemical.

Sodium Metabisulphite (Sodium Pyrosulphite) CAS # 7681-57-4

Sodium Metabisulphite is sometimes referred to

as disodium. It is used as a clearing aid in the gum

bichromate process. It is often found in disinfec-

tants, antioxidants, and preservatives. It may act as

an irritant to eyes and skin but is generally considered

safe. It can be substituted for sodium bisulphite in the

gum clearing stage if needed.

Sodium Selenite CAS# 10102-18-8

Sodium selenite is a white crystal salt solid that is solu-

ble in water. It is very incompatible with strong acids

and mixing should be avoided. The chemical is toxic if

ingested, inhaled, or absorbed through the skin. Wear

adequate safety gear when using this chemical. Sodium

selenite is a primary ingredient in Kodak Rapid Selenium

Toner and will tone silver. If splashed, rinse well. If you

splash the eyes, rinse for 15 minutes. If inhaled, get out

of the lab and breathe fresh air. If swallowed, drink lots

of water and do not induce vomiting. Disposal after

diluting with a large volume of water is acceptable.

Sodium Sulphite CAS# 7757-83-7

Sodium sulphite appears as a white, odorless crys-

tal. This chemical is extensively used in alternative

process wet work as a clearing agent for albumen,

Ziatype, and chrysotype, as a preservative in many

developers, and as a clearing bath for some films

such as Polaroid Type 55 Positive/Negative. It is also

used as a primary component in fixing baths and

presents a very mild health risk. It can be an irritant

to eyes and tissue and will release a sulphur diox-

ide gas if heated. use general safety precautions in

use and handling. It can be substituted for sodium

bisulphite.

Sodium Tetraborate CAS# 1303-96-4

(See Borax)

Sodium Tetrachloroaurate(III) Dihydrate CAS # 13874-02-7

This chemical is used in the Part B solution of the

new chrysotype sensitizer formula and is also known

as sodium chloroaurate and sodium gold chloride. It

is very precious in regard to use with a gram cost in

excess of $82.00. It is corrosive and can be destructive

to your mucous membranes. Take appropriate precau-

tions when working with this chemical, as it may also

cause allergic skin reactions.

Sodium Thiosulphate (Hypo/Fixer) CAS# 7772-98-7

Sodium thiosulphate is a colorless and odorless crystal.

It is also known as sodium hyposulphate or “hypo” and

is incorrectly referred to as hyposulphate of soda since

Herschel’s discovery of it in 1819. It is used in a vast

variety of dilutions depending upon what process you

are using it for, and it is one of the very few substances

that is capable of dissolving silver bromide. Contact

with the skin is not dangerous, but it can decompose

through the action of aging or heat and form a sulphur

dioxide gas that is toxic. Be careful not to let this chem-

ical come into contact with your eyes, and don’t use it

as a fragrance behind the ears as one of my students

once did.

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Sodium Tungstate CAS# 53125-86-3

This chemical, according to MSDS data I have read,

is one that is being tested for human mutations in the

reproductive cycle. It is a primary component in the

Ziatype formula system and will lower contrast in that

process. It is supposedly not highly toxic, but it will cause

general irritation of eyes, tissues, and the respiratory

system if safety precautions are not adhered to.

Sulphamic Acid CAS# 5329-14-6

Sulphamic acid appears as a white and odorless

crystal. It is used as a contrast control in the argyrotype

process and is employed as an acidifier in ammonium

thiosulphate fixing baths. This chemical is corrosive to

tissue, eyes, and the respiratory system. It is highly and

violently reactive when hot and in combination with

nitrates and nitrites. If this sounds like a bomb recipe

then you will take great care not to fool around with

this chemical near an open heat source. Take great

care in using this chemical with gloves, safety glasses,

and a respirator.

Tannic Acid CAS# 1401-55-4

Tannic acid is a yellow/tan powder and may not,

depending on your sensibilities, have an offensive

odor. Personally, I rather like the aroma and think

it smells like instant iced tea mix. This chemical is a

tanning agent and is often used in the toning of cya-

notypes. It is a strong oxidizer of metals, and chronic

exposure is harmful to the liver. It is found in grapes,

tea, and cat urine. It can be irritating to the mucous

membranes, and general caution should be taken

when using it. It is incompatible with albumen, gela-

tin, salts of metals, and strong oxidizers. There is a

low health risk with tannic acid, but be cautious of

the powder’s dust and seek fresh air if you experi-

ence discomfort.

Tartaric Acid CAS# 87-69-4

Tartaric acid is a white, crystalline powder with a strong

fruit acid flavor that is approximately 10% stronger

than citric acid and can be manufactured synthetically

or recovered from natural sources. It is highly soluble

in water but only slightly hydroscopic. This acid gives

apples their sour flavor. It is only mildly toxic, and gen-

eral safety precautions should be used in its handling

and use. Tartaric acid is used in several formulas in

order to prevent highlights from getting muddy. It is not

used for making tartar sauce . . . and I will not relate the

story that goes along with that warning.

Thymol (Phenol, 5-methyl-2-[1-methylethyl]) CAS # 89-83-8

Thymol is used in this book as a preservative for dry

plate film emulsion (see the Alternative Negative chap-

ter). Thymol crystals can also be found online by going

to beekeeping supply vendors. Make sure it is always in

crystal form. Thymol crystals are corrosive and nasty.

Do not purchase thymol in oil of any kind. Thymol

crystals have two distinct uses in British beekeeping,

first as an antifungal or anti-fermentation agent in pro-

ducing sugar syrup feed and secondly as an aromatic

and corrosive sublimation material for use against the

varroa mite in special evaporator frames.

Thymol is only slightly soluble in water, but it is

readily soluble in surgical spirit (rubbing alcohol in

the united States), which is ethanol to which a small

amount of methanol has been added to render it

unfit to drink. It is normally used to sterilize surfaces,

cleanse skin abrasions, and toughen skin. Thymol is a

skin irritant. In the event of a spill or a splash, wash

everything well with warm water for at least 15 minutes

and consider getting medical attention.

3,3’ Thiodipropanoic Acid CAS# 111-17-1

This chemical, with sodium carbonate and water, is the

ligand in the S version of the new chrysotype. It can be

purchased reasonably from the Alfa Aesar company (see

Resources). It is a skin, eye, and respiratory irritant.

Tri-Sodium Phosphate CAS# 7601-54-9

Tri-sodium phosphate is a white, odorless solid and is

strongly alkaline. It is commonly found in photographic

developers, water softeners, scouring powders, laundry

soaps, and dishwashing compounds. In an alterna-

tive process application, it works as a yellow toner for

cyanotypes.

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Tween 20 CAS# 9005-64-5

This is an inexpensive surfactant that may be added

to sensitizers, specifically iron-based processes, and it

helps in getting the sensitizer into the paper fibers. It

can be an eye irritant.

Vinegar

Vinegar strength commonly is measured in “grains.”

In the united States, this refers to the percent acid

times 10. for example, 100-grain vinegar contains

10% acetic acid and 90% water. Distilled vinegar

strength ranges from 50 to 300 grains. Specialty

vinegars range from 40 to 100 grains. The color of

distilled vinegar ranges from a straw color to water

white. Most vinegar is 5%.

A S I M p L E T E S T F O R R E S I D uA L H Y p O / F I x E RA simple test to be sure that all of the sodium

thiosulphate/fixer/hypo is removed from your print

is to make the following solution: 750 ml of water,

125 ml of 28% acetic acid, 7.5 g of silver nitrate, and

cold water to make a liter of solution. Place a drop of

it in the center of a piece of photographic paper that

has experienced the same development, fixing, and

washing as the prints you want to keep. After several

minutes, rinse the paper with a saltwater solution and

examine it for a stain in the drop location. Any color

deeper than a very light tan stain indicates the pres-

ence of hypo. This means that you should wash your

prints longer. Store the solution in a dropper bottle

and use it when you are concerned about the success

of your washing technique.

A S I M p L E T E S T F O R R E S I D uA L S I LV E R u S I N G S O D I u M S u L p H I D Eone way of determining whether or not you have fixed

your print long enough is to give it a simple sodium

sulphide drop test. Mix up a 10% solution of sodium

sulphide (10 g of sodium sulphide with 100 ml of dis-

tilled water) and place a drop of it on a light area of your

image. If the drop of sodium sulphide turns brown, this

means that you still have residual silver salts in your

paper and that additional fixing time is necessary.

R E A D E R R E S p O N S I B I L I T YI have placed warnings and considerations through-

out the entire text to alert you to possible chemical

and health concerns. for a complete overview of all

chemicals in use, and their individual MSDS and

CAS documentation, please refer to the previous

chemical descriptions or to the chemical research

sites that have been provided. These sites have con-

nections and links to many MSDS databases, and

each of these databases has MSDS sheets for individ-

ual distributors of that chemical. If you are a teacher

using these chemicals, you must have MSDS docu-

mentation in your lab. If you have a question or a

concern about a particular chemical, it is solely your

responsibility to find out about that chemical before

using it. It is completely and entirely the responsi-

bility of the reader to take prudent and appropriate

caution in preparation, usage, and disposal when

using chemistry of any kind. Although I have made

every effort to give you clear and safe instructions,

I have no way of knowing if your being is adversely

affected by certain chemicals. If you are unsure of

your sensitivity, or of the chemistry you are about to

use in a process, you must stop and take the respon-

sibility of researching that chemical.

S M A L L VO L u M E C O N V E R S I O N TA B L EThese days, the Internet offers you an abundant

number of electronic conversion sites that make the

following tables redundant and irrelevant. for exam-

ple, check out http://www.unitconversion.org or

http://www.kylesconverter.com. These sites will do

the math instantly for you. All you have to do is to

specify the starting point on the conversion table

(e.g., ounces to milliliters) and type in the number

of ounces, and instantly the equivalent amount in

milliliters will appear. There are charts for every

conceivable conversion. In the event that you do not

have access to the Internet, here are the old school

equivalent figures.

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D RY M E A S U R E1 pound = 453.6 grams

16 ounces = 453.6 grams

1 pound = 16 ounces

16 ounces = 7,000 grains

1 ounce = 28. 35 grams

1 ounce = 437.5 grains

1 gram = 0.77 scruple (apothecary)

1 scruple = 1.3 grams

1 gram = 0.03527 ounce

1 gram = 15.43 grains

10 grams = 154 grains

1 grain = 0.0648 gram

10 grains = 0.648 gram

7 g sugar = 1 tablespoon

10 grams = 154 grains

10 grains = 0.648 gram

100 grains = 6.48 grams

1 gram = weight of 1 ml/1 cc water

1 nickel = 5 grams

1,000 g = 2.2 pounds

♦ To change ounces to grams, multiply (×) ounces

by 28.35.

♦ To change grams to ounces, divide (÷) grams

by 28.35.

♦ To change pounds to grams, multiply (×) pounds

by 453.6.

♦ To change grains to grams, multiply (×) grains

by 0.0648.

♦ To change grams to grains, divide (÷) grams

by 0.0648.

♦ To change grams to milligrams, multiply (×) grams

by 1,000.

♦ To change milligrams to grams, divide (÷)

milligrams by 1,000.

L I Q U I D M E A S U R E1 gallon = 4 quarts or 128 fluid ounces (fl oz)

1 gallon = 3.785 liters or 3,785 milliliters (ml)

1 quart = 32 fl oz

1 quart = 946 ml

1 liter = 1,000 ml

1 liter = 33.81 fl oz

1 cup = 240 ml

4 cups = 950 ml

1 pint = 16 fl oz

1 pint = 473.12 ml

1 fluid oz = 29.57 ml (USA)

1 fluid oz = 28.41 ml (GB)

1 fluid oz = 8 fluid dram

1 tbs = 15 ml/15 cc

3 tsp = 1 tablespoon (tbs)

1 tsp = 5 ml/5 cc

1 dram = 3.697 ml

1 ml = 1 cc (cubic centimeters)

1 cc = 1 ml

1 ml of water = 1 gram (dry weight)

100 ml = 3.38 fl oz

20 drops = 1 ml/1 cc/20 minums

(use a plastic dropper for consistency)

1 drop = 0.067 ml/1 minum

Ounces & Milliliter Conversions

♦ To change ounces to milliliters, multiply (×) ounces

by 29.57.

♦ To change milliliters to ounces, divide (÷) milliliters

by 29.57.

Making a Saturated Solution

A saturated solution is one in which a specific chem-

ical is added to a volume of water until no more

of that chemical will dissolve and in which sedi-

ment remains in the liquid solution. An example of

seeking a saturated solution is when you are mix-

ing up potassium or ammonium dichromate to use

as an ingredient in a gum bichromate sensitizer.

dichromates are used in a saturated solution in

gum printing. Ammonium dichromate is saturated

at around 25%–30% and potassium dichromate at

10%–13%. If you had 100 g of potassium dichromate

and you stirred that chemical into 1,000 ml of water

you would begin to see evidence of saturation in that

10% solution.

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T E M P E R AT U R E C O N V E R S I O N STo Convert Fahrenheit ( F˚) into Centigrade (C˚)

1. Subtract (−) 32 from F˚ temperature.

2. multiply (×) that number by 5.

3. divide (÷) this number by 9 to get the C˚

conversion.

Example: 100°F minus 32 = 68, times 5 = 340,

divided by 9 = 38°C

Equals: 37.77°C

To Convert Centigrade into Fahrenheit

1. multiply (×) Centigrade temperature by 9.

2. divide (÷) that number by 5.

3. Add 32 to that number and get the F˚ conversion.

Example: 38°C times 9 = 342, divided by 5 = 68.4,

plus 32 = 100°F

Equals: 100.4°F

H OW TO F I G U R E P E R C E N TA G E SFor figuring percentages, I now use an iPhone app

called Soulver that is so so much better for me than

pencil and paper: http://www.acqualia.com/soulver/

iphone/.

Percentage (%) is a term applied to expressing the

concentration of a given solution in which a specific

chemical weight has been stirred into a specific volume

of liquid. It defines the number of parts in a particular

compound when added to 100 parts of a solution. In

other words, if you needed to make a 10% solution of

potassium dichromate, you would simply add 10 g of

potassium dichromate to water until you had a total

liquid volume of 100 ml. This is called percent weight

per volume (% w/v).

Percentages Can Be Expressed in Three Different Ways

♦ % w/v (percent weight per volume): This is used

when combining a solid with a liquid.

♦ % v/v (percent volume per volume): This is used

when combining two liquids. For instance, a 30 %

solution of hydrogen peroxide would comprise

30 ml of hydrogen peroxide in 100 ml of water.

♦ % w/w (percent weight per weight): Seldom used

as a measurement, this refers to g of a given com-

pound per 100 g of a given solution. As 1 ml of

water has a weight of 1 g, it is not uncommon for g

and milliliters to replace one another.

Figuring a Percentage for a Solution

Here’s a quick elementary reference for you to use if

you need to make a liter of 15% solution of sodium

thiosulphate. multiply 1,000 by 0.15 and you will get

150. mix 150 g of sodium thiosulphate into the liter of

water for the solution.

If you need to make a liter of 3% solution of sodium

thiosulphate, multiply 1,000 by 0.03 and you will get

30. mix 30 g of sodium thiosulphate into the liter of

water for the solution.

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