any flame. Use a water bath or electric hot plate.

Control of Fire Caused by Flammable Chemicals

Best controlled by smothering them. Use sand, thick blanket

or the now available multipurpose fire extinguishers.

Pouring water on such fires will spread them. Every

laboratory should be equipped with the commercially

available fire extinguishers. If these are not available, there

should be sand buckets in accessible places.

Corrosive Chemicals

These include strong acids, e.g. concentrated sulfuric

acid, hydrochloric acid, nitric acid, glacial acetic acid,

trichloroacetic acid, orthophosphoric acid, and strong

alkalies like sodium hydroxide and potassium hydroxide.

Storage

Store these at low levels.

Safe Use

Never attempt mouth pipetting. Accidental swallowing

can be lethal as these chemicals cause destruction of

living tissue. Always pour a corrosive chemical at below

eye level, slowly, and with great care to avoid splashing.

Wear protective eye glasses/eye shields while opening

such containers. Always add the corrosive substance to

water and that too slowly. The addition of small amount of

water to sulfuric acid is enough to produce sufficient heat

to break a glass container.

Laboratory 9

Toxic, Harmful, and Irritating Chemicals

These are chemicals that can cause death or serious illhealth if swallowed or inhaled or if they come in contact

with skin. Examples are potassium cyanide, mercuric

nitrate, sodium azide, sodium nitroprusside, formaldehyde

solution, chloroform, barium chloride and methanol.

Iodine and sulfuric acid also fall in this category. Skin and

mucous membrane irritants are xylene, formaldehyde and

ammonia vapors.

Storage

Store highly toxic chemicals, e.g. potassium cyanide in a

locked cupboard. Stock solutions should also be stored

safely in a cupboard, not on an open shelf.

Safe Use

Always wear protective gloves and after working with

them immediately lock them up. Always wash your

hands after using a toxic or harmful chemical. Keep fume

forming chemicals in a fume cupboard. Never mouth

pipette them.

Oxidizing Chemicals

These include chlorates, perchlorates, strong peroxides,

potassium dichromate, and chromic acid.

Storage

Keep these away from organic materials and reducing

agents. They can produce much heat when in contact with

other chemicals, especially flammable chemicals.

FIG. : General laboratory

SIGNS FOR MEDICAL LABORATORIES

10 Concise Book of Medical Laboratory Technology: Methods and Interpretations Safe Use

Handle them with utmost care. Most of them are dangerous

to skin and eyes and when in contact with reducing agents.

Explosive Chemicals

These chemicals can explode on being heated or on getting

exposed to flame or friction. A good example is picric acid,

which must be stored under water. If picric acid is allowed

to dry, it can explode.

Carcinogens

These chemicals can cause cancer by ingestion, inhalation,

or by skin contact. Such chemicals include benzidine,

O-toluidine, O-dianisidine, a and b naphthylamine, nitrosamines, nitrosophenols, nitronaphthalenes, and selenite.

The carcinogenic risk is directly proportional to the length

and frequency of exposure and the concentration of the

chemical.

Storage

Label their containers “CARCINOGENIC” and handle

with special precautions.

Safe Use

Must wear protective plastic or rubber gloves, a facemask

and eyeshields when handling carcinogenic chemicals.

Do not let them come in contact with skin. After handling

a carcinogen, wash well in cold water all the apparatus,

bench, bottles and protective gloves (before removing

them) and change your overall. Rinse your hands in cold

running water before using soap. Should a carcinogen

come in contact with skin, wash the affected part in cold

running water for 5 minutes.

ACCIDENTS IN THE LABORATORY

They may be caused by:

1. Acids }

• Splashes on the skin

or • Splashes in the eye

2. Alkalis • Swallowing

3. Toxic substances

4. Heat • Open flames

• Hot liquids

• Inflammable liquids

• Explosions

FIG. : Laboratory cautionary

Laboratory 11