As is well known, the mantle is
composed of the oxides of certain "rare earths" which owe their practical
value to the fact that they are non-volatile at the temperature of the
gas-flame. When a gas containing phosphorus is burnt beneath such a
mantle, the phosphoric anhydride attacks those oxides, partially
converting them into the respective phosphates, and these bodies are less
refractory. A mantle exposed to the combustion products of crude
acetylene soon becomes brittle and begins to fall to pieces, occasionally
showing a yellowish colour when cold. The actual advantage of burning
acetylene on the incandescent system is not yet thoroughly established--
in this country at all events; but it is clear that the process will not
exhibit any economy (rather the reverse) unless the plant is provided
with most capable chemical purifiers. Phosphorus, sulphur, and ammonia
are not objectionable in crude acetylene because they confer upon the gas
a nauseous odour. From a well-constructed installation no acetylene
escapes unconsumed: the gas remains wholly within the pipes until it is
burnt, and whatever odour it may have fails to reach the human nostrils.
A house properly piped for acetylene will be no more conspicuous by its
odour than a house properly piped for coal-gas.
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