Chapter

LABORATORY SAFETY

A. General Considerations

In the laboratory the chemist works with many potentially dangerous substance. Yet, with

constant alertness, awareness of potential hazards, and a few common-sense precautions,

laboratory operations can be carried out with a high degree of safety.



Most of the responsibility for the personal safety of the laboratory worker rests on the worker

himself. In the event of an accident resulting from his neglect of appropriate precautions or

disregard of laboratory regulations he is in a poor position to collect damages for his own

injuries, and may even find himself the target of civil or criminal action if his negligence

results in injury to others. Worse, injuries sustained in laboratory accidents can result in

permanent disability, disfigurement, blindness, or death - - a fact that far transcends legal

considerations.



The basic rule of safety in the laboratory is : be alert - -stay alert ; the laboratory is no

place for the "absent - minded professor". Beyond this, take the trouble to understand what

you are doing and to know what the hazards are, take the appropriate precautions, and use the

appropriate protective equipment.



We summarize here some of the more important specific laboratory rules and precautions.



(1)Never work in the laboratory alone. Before working in the laboratory outside regular hour

be sure that this is permissible and be certain that someone else will be in the same room to

provide assistance in case of need.



(2)At all times wear approved eye protection: "safety glasses" with impact-resistant lenses in

approved frames, or protective goggles, or a face shield, or some combination of these. It

should be borne in mind that this is required by Massachusetts state law. Safety glasses may

be obtained either ground to prescription or non-refracting. Side shields of transparent plastic

may be clipped on for additional protection. Ordinary prescription glasses provide about the

same protection against spatter as do safety glasses but in the event of an explosion the

lenses of ordinary glasses are much more easily shattered and the glass fragments may be

driven into the eyeball; in such a case they can be worse than no glasses at all. Contact

lenses (especially the corneal type) provide negligible protection, and indeed their use may

seriously aggravate hazards from spatter since they will impede washing the cornea free of

caustic liquids that creep or diffuse under them. It is inadvisable to wear them even under

safety glasses, which (it must always be remembered) do not by themselves provide one

hundred percent protection from spatter at top, sides, and bottom.



(3)Use the fume hood for all operations involving poisonous or offensive gases or fumes, as

well as operations involving highly inflammable or potentially explosive materials. A

combination of a fume hood and a safety shield (see below) will provide the maximum readily

available protection against minor laboratory explosions.



(4)Guard against injury from explosion, implosion, flash fires, and spatter cf dangerous liquids

by interposing a "safety shield" or other effective barrier between all personnel and any setup

presenting such hazards. Vacuum distillations of more than small (about 100 ml ) quantities

should be shielded, as should gas scrubbing trains containing significant size such as vacuum

desiccators.



(5)Use a metal safety pail with a well-fitting cover to transport any dangerous liquid, or more

than a small quantity (a pint) of any solvent. Several years ago the writer was a witness to a

fatal accident in which a sealed bottle of ethyl chlorocarbonate, C2H5OCOCl, blew up (from

internal CO2 pressure) in the face of a technician who was carrying it in one hand from the

dangerous chemicals vault. A safety pail would probably have saved her life.



(6)Never heat an organic solvent in an open vessel over an open flame; keep a respectable

distance between open vessels containing organic solvents and any open flames or sources of

sparks. Except under special circumstances, an open flame should not be used to heat a

reaction apparatus containing inflammable materials.



(7)Never place beakers or unstoppered flasks containing chemicals in a refrigerator, even if it

is of the "explosive proof" type, or in any other unventilated enclosure. Never store volatile

toxic materials in a refrigerator or other unventilated enclosure even in a "stoppered" vessel.

The first breath a person takes after opening the refrigerator door could be his last.



(8)Do not work with large quantities of reactants (i. e. more than about 100g) unless you have

received special instruction regarding large-scale reactions.



(9)Always be careful to avoid pointing the mouth of a vessel being heated toward any person,

including yourself.



(10)Exept for certain operations for which special instruction should be obtained beforehand

(reduced-pressure distillations, reactions in bombs or sealed tubes, etc.)never heat reactants of

any kind in a fully closed system; be sure the system is open to the air at some point to

prevent pressure buildup from boiling or gas evolution.



(11)Never add anything To a concentrated acid, caustic, or strong oxidant; instead add the

acid, caustic, or oxident slowly and cautiously to the other ingredients, preferably no faster

than it is consumed by reaction.



(12)Never add solids (boiling chips, charcoal, etc.) to a hot liquid as this may result in violent

boiling if the liquid happens to be superheated. perform such additions (or put in an

appropriate ebullator) when the liquid is still at room temperature.



(13)Never pipette by mouth any toxic or corrosive substance or (preferably) anything else. Use

an automatic pipette or fill a conventional pipette with a rubber bulb. (Exceptions to this can

be made for certain dilute non-toxic or slightly toxic solutions used in analytical work: HCl,

NaOH, NaCl, NaHCO3, Na2S2O3, etc. If some of any such solution gets into the mouth it will

be sufficient to spit it out and wash the mouth out well with water.) Assume any unfamiliar

substance to be toxic unless you know definitely to the contrary.



(14) Be sure all chemical containers are correctly and clearly labelled. Labels for your

preparations should contain, besides the name or formula of the contents: your name, the date,

and a sample number by which it can be identified