2 per cent. of sulphuretted hydrogen, which
kills in less than two minutes. But this refers only to crude acetylene
undiluted with air; and being a hydrocarbon--being in fact neither oxygen
nor common air--acetylene is irrespirable of itself though largely devoid
of specific toxic action. Numerous investigations have been made of the
amount of acetylene (apart from its impurities) which can be breathed in
safety; but although these point to a probable recovery after a fairly
long-continued respiration of an atmosphere charged with 30 per cent. of
acetylene, the figure is not trustworthy, because toxicological
experiments upon animals seldom agree with similar tests upon man. If
crude acetylene were diluted with a sufficient proportion of air to
remove its suffocating qualities, the percentage of specifically toxic
ingredients would be reduced to a point where their action might be
neglected; and short of such dilution the acetylene itself would in all
probability determine pathological effects long before its impurities
could set up symptoms of sulphur and phosphorus poisoning.
Ammonia is objectionable in acetylene because it corrodes brass fittings
and pipes, and because it is partially converted (to what extent is
uncertain) into nitrous and nitric acids as it passes through the flame.
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