is thermodynamically unstable and is sensitive to shock and pressure. Its stability is enhanced by the presence of small amounts of other compounds such as methane, and acetylene in cylinders is relatively safe to handle because it is dissolved in acetone. Acetylene fires can be fought with carbon dioxide, dry chemical, and halon extinguishers; firefighting is greatly facilitated by shutting off the gas supply.

Reactivity and Incompatibility

Acetylene forms highly unstable acetylides with many metals, including copper, brass, mercury, potassium, silver, and gold. The dry acetylides are sensitive, powerful explosives. Acetylene may react violently with fluorine and other halogens (chlorine, bromine, iodine) and forms explosive compounds on contact with nitric acid.

Storage and Handling

Acetylene should be handled in the laboratory using the "basic prudent practices" described in Chapter 5.C, supplemented by the additional precautions for dealing with extremely flammable substances (Chapter 5.F) and compressed gases (Chapter 5.H). In particular, acetylene should be used only in well-ventilated areas free of ignition sources. Acetylene is supplied in specially designed steel cylinders containing acetone and an inert material. More than 1 liter of the gas should never be stored in other containers. Brass or copper tubing, valves, or fittings should never be allowed to come in contact with acetylene. If acetylene must be purified, it should be passed through concentrated H2SO4 and NaOH (do not use activated carbon).

Accidents

If large amounts of this compound are inhaled, move the person to fresh air and seek medical attention at once.

In the event of an acetylene leak, shut down and remove all ignition sources and ventilate the area at once to prevent flammable mixtures from forming. Carefully remove cylinders with slow leaks to remote outdoor locations. Limit access to an affected area. Respiratory protection may be necessary in the event of a large release or a leak in a confined area.

Disposal

Excess acetylene should be returned to the vendor for disposal; disposal should not be attempted in the laboratory. Excess acetylene should be vented from reaction flasks, tubing, etc., rather than scrubbed with strong base to avoid the formation of acetylides. For more information on disposal procedures, see Chapter 7 of this volume.



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