 |
|
ABC of Safety in the Biological Sciences
ACIDS
Mineral acids are said to be responsible for more accidents in the laboratory than any other liquids.18 Acids and their vapours are corrosive and can produce severe damage to eyes and body tissues. All concentrated acids are dangerous but hydrofluoric acid, in particular, is extremely corrosive and toxic as a liquid or vapour.
Of the more commonly used acids sulphuric acid needs to be handled with extreme care as it reacts violently with water. When diluting an acid always add acid to water and never pour water into acid. When handling acids always wear a long sleeved laboratory coat or gown, rubber gloves pulled over the sleeve of the coat or gown and full face protection. Use a fume hood and ensure that it is working correctly.
Stoppers
Great care needs to be taken if a stopper is
found to be firmly fixed in the neck of a bottle. This often occurs
with concentrated acids, particularly when glass stoppers are used
in glass bottles.
The safe procedure to follow when removing
a problem stopper is as follows:
1. Stand the bottle in a large sink.
2. Cover the stopper and the neck of the
bottle with a cloth.
3. Gently tap the stopper. If the stopper in
the bottle is glass use another glass stopper to tap it with. The
two glass stoppers set up a resonance which is often successful in
loosening the jammed stopper.
4. If these measures fail it will be necessary
to break the neck of the bottle after scoring around it with a glass
file. A point of hot glass applied to the score mark will cause the
neck to break cleanly.
A releasing solution19 can be applied to the stopper although this normally takes several hours to be effective.
METHOD
Absolute ethanol 2 parts
Glycerin 1 part
Sodium chloride 1 part
Carrying
Bottles containing acid should be transported
in carriers designed for that purpose. These have a cap which locks
in place over the bottle holding it firmly and securely. Carriers
are manufactured from acid resistant low density polyethylene and
are designed to contain a spill should this occur.
Pouring
When pouring acids never place the stopper
from the bottle on a bench top but rather hold the stopper in the
crook of your hand and replace once pouring is complete.
Pour acids slowly. Do not discharge in spurts. Wear rubber gloves to avoid drips which run down the side of the bottle. After pouring flush the outside of the container with water before storing. Immediately flush any splashes that occur with water and neutralise with a solution of 10% sodium bicarbonate.
Acids rapidly destroy paper labels on bottles. Although etched labels are recommended paper labels coated with a thin layer of paraffin wax or Teflon are suitable.
Storage
Concentrated acids and alkalis are
incompatible and contact between them can be explosive. These agents
should not be stored adjacent to each other. Some acids when mixed
together are also incompatible (see Incompatible Chemicals).
Acids are best stored in cabinets designed to contain spills should a bottle break (see acid storage cabinet). Suitable cabinets have glass reinforced cement in the base.
Spillage's
A face mask, eye protection and rubber gloves
along with appropriate body protection are essential before
attempting to clean up a moderate spillage. Breathing apparatus is
required with some types of acid spills, for example hydrochloric
acid. Spread sodium bicarbonate liberally over the splash area and
when neutralised mop up cautiously with plenty of water. Commercial
products for use in acid spills are also available.
Treatments
If spills occur on the body immediately drench
the affected area with water. An emergency shower should be used for
all but minor spills. After drenching remove clothing and thoroughly
wash the affected areas.
A magnesia/glycerol paste can be applied to any skin affected areas, however blisters and burns will require medical attention.20
If acids are ingested give water to drink followed by milk of magnesia. If only the mouth is involved flush thoroughly with water followed by milk of magnesia.20
If acid vapours are inhaled rest and warmth are required, however if exposure is severe it is necessary to seek medical advice.20
BACK to the top
of the Glossary Contents List
BACK to the top of the Chemical
Contents List