Safety Regulations: Part 3: Common Hazardous Chemicals

Some very common chemicals require special care and a general awareness is needed of the dangers inherent in their use. Representatives of these are listed below in four categories: unstable, highly reactive, flammable and toxic. More details on these and many more chemicals are readily available in the library, prep rooms and research labs.

Material Safety Data Sheets (MSDS) are available from Chemistry Stores.

Unstable Chemicals

(Keep quantities to a minimum; in some cases consider use of safety screens and techniques for handling by remote control.)

• Acetylene and acetylides
• Azides and silvering solutions
• Azo and diazo compounds
• Chlorates and perchlorates
• Chlorides of aluminum, silicon and titanium
• Ethers, dioxane, tetrahydrofuran
• Nitro compounds, picric acid, TNT
• Nitrogen halides (touch sensitive and highly explosive)
• Peroxides (especially concentrated hydrogen peroxide and organic peroxides).

Highly Reactive Chemicals

(Evolved heat may cause corrosive and toxic mixtures to be thrown about, followed by fire or explosion.)

Strong acids

• Concentrated hydrochloric acid (hydrogen chloride in gas cylinders is not to be kept more than 6 months)
• Hydrofluoric acid, hydrogen fluoride
• Nitric and fuming nitric acid
• Sulphuric acid, concentrated

Strong Bases

• Caustic alkalis, calcium oxide
• Ammonia, especially liquid

Halogens

• Especially fluorine and interhalogen compounds

Metallic hydrides and alkyls

• Some metals, especially sodium, potassium and lithium
• Chlorides of non-metals (react violently with water)

Oxidizing agents

• Liquid oxygen, chromic acid, perchloric acid

Flammable chemicals

(Protection required from smokers, hot plates, ovens, refrigerators, static charges.)

Organic solvents and reagents with flash points below 30 °C:

• Acetaldehyde
• Acetone
• Acetonitrile (methyl cyanide)
• Amyl acetate
• Benzene
• Carbon disulphide
• Chlorobenzene
• Cyclohexane
• Cyclohexene
• Dioxane
• Ethanol
• Ethers
• Ethyl acetate
• Methanol
• Methyl ethyl ketone
• Pentane
• Petroleum ether
• Propanol
• Pyridine
• Toluene
• Vinyl acetate
• Xylene

Inorganic

• Alkali Metals
• Metals in finely-divided form OR nanoparticles
• Metal hydrides, alkyls, etc.
• Phosphorus (yellow)

Toxic chemicals (“poison”):

These may be quick-acting or cumulative, or pose risks of dermatitis or cancer. There is a need for very close control of these substances in both use and storage. Corrosive poisons include most substances listed under “Highly reactive”. Materials which are also carcinogenic are marked C:

When large quantities of such chemicals are involved, their use must be so controlled that there is no danger to anyone within or outside the laboratory. This will often require the use of procedures which may seem tedious but which are designed to protect all concerned. The system of control shall be capable of withstanding public examination. Primary rules for work with toxic compounds are:

• Prevent inhalation of vapours or dusts;
• Prevent contact with food or skin;
• Smoking, eating and drinking are forbidden in the laboratory or storeroom;
• Pipetting by mouth is forbidden;
• At the first sign of illness, medical advice must be obtained;
• Toxic substances must be rendered harmless before being discharged down the drain;
• Gloves must worn and the face protected by visor or respirator;
• A second person must be within sight of the work and suitably equipped for taking in an emergency;
• Antidotes shall be readily available;
• Warning signs shall be placed at door of small laboratories and locally in larger ones;
• All possible work shall be done in a fume hood, but a ventilated glove box will give surer protection against toxic dust and powders;
• Quarterly annual safety walks will be conducted by the Safety committee and written observations of safety precautions and violations will be reported to those concerned.