Laboratory rules and chemical safety
A hazard is defined as the potential of a substance to cause harm. Hazards are a property of a substance and cannot be reduced, for example, concentrated sulfuric acid is corrosive, it cannot be changed (although in some situations you might be able to use dilute sulfuric acid which is less hazardous)
(For more details see 'Hazard Warning Symbols' for the common hazards).
Risk is how likely a substance will be harmful under the conditions it is used. Risks can be reduced by using smaller amounts of chemicals and taking precautions such as using fume cupboards.
An effective risk assessment will take into account the hazards involved and who will be at risk. It also addresses the steps needed to minimise risk and will include the safe means of disposal of the substances used or made.
Basic laboratory best practice
Here are a few simple rules that form the basis of good, safe, lab practice. There might be particular procedures however that require special rules. For this reason it is vital to read any laboratory instructions thoroughly and to seek the advice of demonstrators / lab supervisors.
Dos and don’t
Always wear eye protection (safety spectacles or goggles)
Always wear a lab coat and make sure it is buttoned up
Always tie back long hair
Always wear gloves when required (dependent on risk assessment and chemicals used)
Always be aware of hazards and risks
Always clear up spillages immediately
Always minimise risks by working tidily and clean up after the experiment
Use a fume cupboard if necessary
Never work alone or unsupervised
Never eat or drink in the laboratory
Never touch, sniff or taste chemicals
Never wear open-toed shoes or sandals in the laboratory
Never pipette liquids by mouth, always use a safety filler
Never dispose of hazardous materials down the drain, use the appropriate waste containers provided
Never return unused chemicals to their original containers but try to avoid taking more than you need in the first place
Handling chemicals safely
Harmful and toxic chemicals
The difference between a harmful chemical and a toxic one is a matter of degree; chemicals which are particularly harmful are classified as toxic. Harmful and toxic chemicals must always be handled in a fume cupboard with the sash (sliding front) pulled down as far as is practicable to protect yourself from splashes and explosions. It is also essential to wear protective gloves and take particular note of any special instructions about disposal and what to do in case of spillage.
Examples of harmful and toxic materials are aniline (phenylamine), bromine (most aqueous solutions and the pure liquid), chlorofrorm (trichloromethane), methanol and cyanide salts
Many solvents and reagents used in the laboratory are highly flammable and so there should never be naked flames in places where they are being used. The heating of flammable materials should be carried out using electrically heated water baths, heating mantles or hot plates.
Examples of highly flammable solvents are diethyl ether (ethyloxyethane), petroleum ether (a mixture of hydrocarbons, not an ether), toluene (methylbenzene), acetone (propanone) and ethyl acetate (ethyl ethanoate).
Chemicals may irritate the skin, eyes or respiratory system. Those which produce a vapour which irritates the eyes or respiratory system should always be handled in fume cupboards.
Examples of irritants are solid copper sulfate (but it does not produce an irritating vapour), styrene (phenylethene) (which does produce an irritating vapour). Acid chlorides (such as ethanoyl chloride), or thionyl chloride are both corrosive and produce irriating vapours.
The most commonly encountered corrosive materials are acids and alkalis although many other types of chemical fall into this category. It is essential to wear appropriate protective gloves when handling corrosive material and if there is contact with the skin it should be washed off immediately with plenty of water. It may also be necessary to seek medical attention.
Examples of corrosive materials include concentrated and even moderately dilute solutions of mineral acids (hydrochloric, nitric, sulfuric and phosphoric acids) and strong alkalis such as sodium hydroxide and potassium hydroxide.
Oxidising agents are dangerous because they can cause fires if they make contact with any combustible material, particularly if they are disposed of carelessly.
Examples of oxidising agents are solid potassium dichromate(VI), solid potassium manganate(VII), concentrated nitric acid as well as concentrated hydrogen peroxide
Some compounds and mixtures are explosive because they are unstable, particularly if heated or when dry. Others present a risk of causing explosions because they react violently with water. When handling such chemicals it is essential to use only small amounts and protect yourself with a face mask and a safety screen.
Examples of explosion hazards are ammonium dichromate(VI) and gun powder. The alkali metals sodium and potassium present a risk of causing explosions because of their reaction with water.
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The Interactive lab primer has been developed as part of the Royal Society of Chemistry Teacher Fellowship Scheme titled ‘Chemistry for our Future’ in partnership with the University of Southampton, The University of Nottingham, University of Birmingham and The University of Sheffield
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