SUBSIDIARY PURIFYING MATERIALS.--Among minor reagents suggested as
purifying substances for acetylene may be mentioned potassium
permanganate, barium peroxide, potassium bichromate, sodium plumbate and
arsenious oxide. According to Benz the first two do not remove the
sulphuretted hydrogen completely, and oxidise the acetylene to some
extent; while potassium bichromate leaves some sulphur and phosphorus
behind in the gas. Sodium plumbate has been suggested by Morel, but it is
a question whether its action on the impurities would not be too violent
and whether it would be free from action on the acetylene itself. The use
of arsenious oxide dissolved in a strong acid, and the solution absorbed
in pumice or kieselguhr has been protected by G. F. Jaubert. The
phosphine is said to combine with the arsenic to form an insoluble
brownish compound. In 1902 Javal patented a mixture of 1 part of
potassium permanganate, 5 of "sulphuric acid," and 1 of water absorbed in
4 parts of infusorial earth. The acid constantly neutralised by the
ammonia of the crude gas is as constantly replaced by fresh acid formed
by the oxidation of the sulphuretted hydrogen; and this free acid, acting
upon the permanganate, liberates manganese peroxide, which is claimed to
destroy the phosphorus and sulphur compounds present in the crude
acetylene.
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