As a
special acetylene purifier, bleaching-powder exists in at least two chief
modifications. In one, known as "acagine," it is mixed with 15 per cent.
of lead chromate, and sometimes with about the same quantity of barium
sulphate; the function of the latter being simply that of a diluent,
while to the lead chromate is ascribed by its inventor (Wolff) the power
of retaining any chlorine that may be set free from the bleaching-powder
by the reduction of the chromic acid. The utility of the lead chromate in
this direction has always appeared doubtful; and recently Keppeler has
argued that it can have no effect upon the chlorine, inasmuch as in the
spent purifying material the lead chromate may be found in its original
condition unchanged. The second modification of bleaching-powder is
designated "puratylene," and contains calcium chloride and quick or
slaked lime. It is prepared by evaporating to dryness under diminished
pressure solutions of its three ingredients, whereby the finished
material is given a particularly porous nature.
It will be observed that both heratol and frankoline are powerfully acid,
whence it follows they are capable of extracting any ammonia that may
enter the purifier; but for the same reason they are liable to act
corrosively upon any metallic vessel in which they are placed, and they
therefore require to be held in earthenware or enamelled receivers.
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