ABC of Safety in the Biological Sciences
Handling Hazardous Chemicals
ALL chemicals are hazardous to some degree. Protect
yourself from accidental skin, eye, and respiratory contact by
wearing appropriate protection which should always include a long
sleeved laboratory coat or gown with elasticised wrist bands, rubber
gloves and safety goggles. Contact lenses should not be worn when
Know the hazards of the materials you are working with. Always
source appropriate safety information from a Material Safety Data
Sheets, (MSDSs), before handling an unknown chemical or before
attempting disposal or clean-up procedures.
Handling of Organic Peroxides
- Whenever possible, perform hazardous reactions in a properly
functioning hood using appropriate shielding.
- Never taste a laboratory chemical.
- Take special precautions when scaling up a reaction. A
reaction that is safe under published conditions may be violent
when multiplied in scale.
- Read labels carefully, and keep labels clean so that they
are legible. Replace deteriorating labels before a chemical
- Clearly labels ampoules, product vials, reaction vessels,
and all other containers. Labels should include chemical names,
structures when appropriate, date and name of owner. If you know
of special risk, include appropriate warnings. Unidentified
materials cannot be disposed of and can cause serious accidents.
- If it is necessary to smell a chemical, do so by wafting the
vapors toward your nose with your hand so that the minimum
amount is inhaled.
- Never pour a chemical back into its original bottle after
measuring out too much. This can contaminate the original
- Never combine the contents of two or more bottles of the
same reagent. If one of the bottles is contaminated, the
resulting combination is now contaminated.
- Be aware of chemical incompatibilities before mixing to
avoid explosive or uncontrollable reactions, generation of toxic
Peroxides are a group of compounds that contain an oxygen-oxygen
bond. As a class, organic peroxides are the most explosive
substances normally found in a laboratory. Peroxides are sensitive
to light, heat, and friction, as well as to strong oxidizing and
reducing agents. Explosions involving peroxides are unpredictable
and usually violent.
- Store peroxides away from sources of light, heat, friction,
and mechanical disturbance.
- A solid peroxide can often be stored more safely if it is
dissolved in a nonperoxidizable inert solvent such as an
- Do not allow solutions of peroxides to evaporate, because
the concentration of peroxide may reach a dangerous level.
- Store solutions of peroxides at a cool temperature, but do
not refrigerate peroxides at a temperature below which
precipitation or freezing out of solid material may occur; in
this form, peroxides are extremely sensitive to shock and heat.
- Do not store peroxides or solutions of peroxides in glass
bottles with ground glass or screw caps. The friction caused by
opening the bottle can initiate an explosion. Polyethylene
bottles with screw caps are more suitable.
- Use ceramic spatulas for handling peroxides; metal spatulas
can catalyze an explosive reaction.
- Never use a naked flame in areas where peroxides are being
- Purchase, store, and use the minimum quantity of peroxide
necessary. Use special caution when scaling up reactions that
- Perform experiments involving peroxides in a hood and behind
a safety shield.
- Clean up all spills immediately by absorption on vermiculite
or other suitable absorbent.
Peroxide-forming Chemicals -- Some
chemicals can easily form peroxide when exposed to atmospheric
oxygen. These peroxidizable chemicals are especially dangerous
because the presence of peroxides may not be known. Check this
peroxidisable compounds before using an organic solvent in a
distallion or reaction.
Handling of Peroxide-forming Chemicals
Handling of Common Chemicals that are
- Buy and use the minimum quantities of Peroxidizable
- Store peroxide-forming chemicals for the shortest possible
time. Date the container when it is opened. Test for peroxide
formation when first opened and every 3 months. If peroxide
levels are acceptable, date the container when the test was
performed. If the material contains hazardous concentrations,
either treat to remove peroxides or discard.
- Peroxide formation in ethers and hydrocarbons can be
prevented if they are stored under an inert atmosphere, for
example, argon or nitrogen. The container should be well sealed.
- Store peroxidizable chemicals away from source of heat,
light, sparks, other ignition sources, and mechanical shock.
- Peroxide-forming compounds should be kept at a cool
temperature. Do not refrigerate peroxides if solid peroxide may
precipitate or freeze out. Solid material is especially
sensitive to shock.
- Do not store peroxide-forming compounds in glass bottles
having ground glass or screw caps, or metal cans with metal
screw caps. Serious explosions can occur by merely unscrewing
the top of a glass bottle that contains peroxides. Metal cans
with plastic caps and polyethylene bottles are safer containers
for ethers and other peroxidizable compounds. The safest
container is the one supplied by the manufacturer.
- Test peroxidizable substances before using, and periodically
- Peroxides may be removed from solvents by passing the
solvent through a column of alumina or Dowex-1 resin. The column
MUST NOT be allowed to run dry and the packing should be handled
as other peroxide waste. It is less dangerous, however, to use a
new bottle of peroxide-free solvent than to purify solvent
- Serous accidents can occur when substances capable of
forming peroxides are distilled. Consider other methods of
purification. If distillation is necessary, the following
precautions should be observed where peroxide formation is
- Test for peroxides before distilling. The peroxide test
strips can indicate the concentration of peroxide in ppm.
allowing you to know just how much peroxides are present.
- Do the distillation under an inert atmosphere. Do not
allow air to come in contact with hot solvent.
- Add a suitable reducing agent to the distillation flask,
such as sodium/benzophenone for ethers. Make sure that no
compounds that react vigorously with the reducing agent are
present in the distillation flask.
- Do not carry the distillation to dryness; leave at least
10% liquid in the flask.
- Wear goggles, face shield and use a free standing safety
shield when distilling peroxidizable chemicals. Conduct the
distillation in a hood with the sash closed.
- Be aware that freshly distilled peroxidizable material
may reform peroxide with two weeks of distillation.
- Spills should be cleaned up immediately by absorption on
solusorb or other suitable absorbents. These are located in the
issue rooms or main stockroom.
Many compounds found in older literature have been found in recent
years to be more hazardous than once thought. When the research was
preformed, these compounds were readily available and the chronic
effects were not known. Therefore, if you use a procedure not
recently published, you must check the MSDSs of the reagents to get
the most recent information on hazardous health affects. For the
compounds listed below, consider finding a substitute solvent or
reactant to avoid possible risk. If you cannot find a substitute,
then take special precaustions to avoid exposure.
- Benzene is considered a Category I Carcinogen by
OSHA. Chronic poisoning can occur by inhalation of relatively
small amounts over a long period of time. The toxic action is
primarily on the blood-forming organs. Benzene has been
documented to cause leukenia. Benzene is readily absorbed
through the skin. Toluene should be substituted whenever
possible. OSHA permissible exposure limit is 1 ppm.
- Carbon Tetrachloride is another dangerous solvent
found in many literature references. At one time, carbon
tetrachloride was used in fire extinguishers (if you ever find
an old extinguisher with CCL4, contact the Chemical Hygiene
Officer immediately). Keep exposure to the liquid and its vapors
to an absolute minimum. High concentration in the air can lead
to death from respiratory failure. Less severe exposure can lead
to kidney and liver damage. In addition to inhalation hazard, it
can be readily absorbed through the skin. Methylene chloride,
(dichloromethane), is a much safer chlorinated hydrocarbon.
However, almost all chlorinated hydorcarbons have been found to
be toxic to some degree. The current threshold limit value for
carbon tetrachloride is 5 ppm.
- Chloroform is a compound similar to carbon
tetrachloride with one less chlorine atom (CHCL3). Therefore, it
has many of the adverse health affects as carbon tetrachloride.
Repeated exposure can cause kidney, liver and heart damage. In
laboratory animals it has been shown to be a carcinogen and
mutagen. Use methylene chloride as a substitute. The PEL for
chloroform is 2 ppm.
- Formaldehyde use as preservative of biological tissue
has been found to be a a human carcinagen. Repeated inhalation
can cause cancer of the lungs, nasopharynx, and/or nasal
passages. It can cause respiratory tract irritation and edema.
It can also cause eye and skin irritation. Formaldehyde is a
colorless, pungent, ittitant gas that is water soluble and most
frequently found in 37% aqueous solution commonly known as
formalin. Alway use formalin in a hood and wear gloves and
splash-proof goggles. The threshold limit value for formaldehyde
is 0.75 ppm.
- Ethyl ether is an extremely flammable solvent use in
Grinard reactions and extractions. The greatest danger of ethyl
ether is its very low flash point (-30 C). The vapors of ether
are heavier than air and can "crawl" along the benchtop to a
source of ignition. Tends to form peroxides especially
anhydrous. It is a depressant to the central nervous system and
can cause unconciousness or even death on severe exposure. Carry
out reactions using ethyl ether in the hood.
- Perchloric Acid usually found as 72% aqueous solution
is a very strong non-oxidizing acid. Contact with combustible
materials at elevated temperatures may cause fire or explosion.
Handle with extreme care as severe burns can result from skin
contact. Wear heavy rubber gloves and apron in addition to
BACK to the top
of the Glossary Contents List
BACK to the top of the Chemical