Warning sign

Meanings:

a. Explosive
Substances which may explode if ignited, heated or under a shock or friction.

Examples:
Old stocks of potassium and sodium which have turned yellow, ammonium dichromate.

Safety precautions:
Keep away from heat and naked flame.
Avoid shock or friction.


b. Irritant
Non-corrosive substances which may cause reddening or inflammation of the skin.

Examples:
Bench dilute mineral acids, ammonia solution.
Anhydrous iron (III) chloride, ammonium dichromate, potassium dichromate.

Safety precautions:
Avoid contact with the eyes or skin; when accidentally spilt into the eyes or onto the skin, wash the affected area with plenty of water.


c. Toxic
Substances which may cause serious health risk or even death if breathed in, swallowed, or absorbed through the skin.

Examples:
Chlorine, hydrogen sulphide, carbon monoxide, nitrogen dioxide.
Bromine tetrachloromethane, methanal solution (37%).

Safety precautions:
Perform the experiment in fume cupboard.
Avoid breathing in their gases/vapours/particles.
Wear gloves (if gloves are not used, wash hands thoroughly after handling chemicals).


d. Nuclear
Substances that are radioactive, have potential danger on human.

Examples:
Uranium salts


e. Oxidizing
Substances which give out a lot of heat when reacting with other materials. It causes a fire risk.

Examples:
Concentrated nitric acid.
Nitrates, potassium permanganate.

Safety precautions:
Keep away from heat and naked flames.
If concentrated acid is spilt into the eyes or onto the skin, wash the affected area with plenty of water.


f. Harmful
Substances which may cause less serious health risk.

Examples:
Trichloromethane, 1,1,1-trichloroethane.
Iodine, lead componds, barium compounds (except barium sulphate), oxalic acid, oxalates.

Safety precautions:
Avoid breathing in their vapours/particles.
If accidentally spilt into the eyes or onto the skin, wash the affected area with plenty of water.
The laboratory should be well ventilated.


g. Flammable
Substances that may easily catch fire under normal conditions.

Examples:
Hydrogen, carbon monoxide, methane, LPG, town gas.
Methanol, ethanol, ethyl ethanoate, propanone, benzene.
Yellow phosphorus, potassium, sodium.

Safety precautions:
Keep away from heat and naked flames.
Stored in well ventilated place.


h. Corrosive
Substances which may destroy living tissues upon contact.

Examples:
Hydrogen chloride.
Bromine, concentrated mineral acids, concentrated ethanoic acid, concentrated ammonia solution.
Potassium, sodium, yellow phosphorus, iodine, sodium hydroxide, potassium hydroxide, silver nitrate.

Safety precautions:
Wear a laboratory coat, safety spectacles and gloves.
Perform the experiment in fume cupboard.
Avoid contact with the eys and the skin; when accidentally spilt into the eyes or on the skin, wash the affected area with plenty of water.

Harmful - causeing damage or injury to somebody
Irritant - a substance that makes part of your body sore
Toxic - containing poison
Nuclear - producing from nuclear energy
Oxidizing - to combine with oxygen
Explosive - easily able to explode
Flammable - that can catch fire easily
Corrosive - tending to destroy something slowly by chemical action