If the acetylene passes into the
ordinary gasholder, the amount of phosphine in gas drawn off from the
holder will vary from time to time according to the temperature and the
degree of saturation of the water in the holder-tank with phosphine, as
well as according to the amount of phosphine in the gas generated at the
time.
A method frequently employed for the determination of phosphine in
acetylene is one devised by Lunge and Cedercreutz. If the acetylene is to
be evolved from a sample of carbide in order to ascertain how much
phosphine the latter yields to the gas, about 50 to 70 grammes of the
carbide, of the size of peas, are brought into a half-litre flask, and a
tap-funnel, with the mouth of its stem contracted, is passed through a
rubber plug fitting the mouth of the flask. A glass tube passing through
the plug serves to convey the gas evolved to an absorption apparatus,
which is charged with about 75 c.c. of a 2 to 3 per cent. solution of
sodium hypochlorite. The absorption apparatus may be a ten-bulbed
absorption tube or any convenient form of absorption bulbs which subject
the gas to intimate contact with the solution. If acetylene from a
service-pipe is to be tested, it is led direct from the nozzle of a gas-
tap to the absorption tube, the outlet of which is connected with an
aspirator or the inlet of an experimental meter, by which the volume of
gas passed through the solution is measured.
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