Warning signs on laboratory chemicals and apparatus

Some of the chemicals and apparatus used in biology laboratory may be harmful or dangerous. Before starting using any chemical you must know whether the chemical is toxic, flammable, oxidizing, explosive or irritant/harmful. To help you recognize such dangerous substances, the containers of modern chemicals carry special chemical warning signs as indicated below. 


Toxic 

Toxic substances can cause death. They may be poisonous when swallowed, breathed in or absorbed through the skin. Examples of toxic substances include acids and alkalis, lead II acetate and potassium dichromate. 
The symbol for toxic substances is represented as shown below. 



Flammable 


Flammable substances are substances which can catch fire easily. Examples of such substances include petrol, alcohol, Thomas Baker (Phosphorus yellow or phosphorus red) and potassium metal. These substances normally evaporate fast and therefore should not be brought near open flames. The symbol is as indicated above.



Corrosive 

Corrosive substances attack and destroy living tissues. They may destroy the floor, desks as well as metals, examples of corrosive substances are concentrated acids, e.g. sulphuric acid, hydrochloric acid, nitric acid and concentrated alkalis e.g. sodium, potassium and ammonium hydroxides. If by accident a corrosive substance comes into contact with your skin, go to the sink and wash with a lot of water. The symbol is shown below.



Oxidant

An oxidant is a chemical or substance which accelerates burning. Small fires can be made big in the presence of oxidizing agent. Examples of oxidizing agents include potassium permanganate, potassium chlorate, and zinc nitrate.



Explosive 

An explosion is a forceful rapid reaction which involves random throwing of particles.



Harmful or irritant 

Harmful substances have a long term effect. They do not kill immediately. They have a cumulative effect. Therefore careful handling is required.


Irritant substances cause pains on the skin or eyes. They can endanger one's health if they come into contact with the skin or eyes for too long. Examples of harmful substances include lead chloride, lead nitrate, lime water ferrous sulphate and manganese (IV) oxide.


Examples above of some chemical containers with their warning signs.