team to form sulphuric
acid, again combine with more oxygen, and so on. The exact processes or
reactions are of course much more complicated, but the above represents
what is practically the ultimate result. It is evident that the gases
leaving the last lead chamber in which the formation of vitriol is
effected, must still contain nitrous fumes, and it becomes a matter of
importance to recover them, so that they can be used over again. To
effect this object, use is made of the solubility of nitrous fumes in
strong vitriol. The gases from the last lead chamber of the series are
passed through what is called a Gay-Lussac tower (the process was
invented by the eminent French chemist Gay-Lussac), which is a tower
made of lead, supported by a wooden framework, and filled with coke or
special stoneware packing, over which strong vitriol is caused to flow.
The vitriol dissolves the nitrogen oxides, and so-called "nitrous
vitriol" flows out at the base of the tower. The recovery of the
nitrogen compounds from the nitrous vitriol is effected in Glover towers
(the invention of John Glover of Newcastle), which also serve to
concentrate to some extent the weak acid produced in the lead chambers,
and to cool the hot gases from the sulphur burners or pyrites kilns. The
weak chamber acid is mixed with the nitrous vitriol from the Gay-Lussac
tower, and the mixture is pumped to the top of the Glover tower, which
is of similar construction to the Gay-Lussac tower, but is generally
packed with flints. This Glover tower is placed between the sulphur
burners or pyrites kilns and the first lead chamber. The nitrous vitriol
passing down the tower meets the hot gases from the kilns, and a
threefold object is effected: (1) The nitrous fumes are expelled from
the nitrous vitriol, and are carried into the chambers, to again play
the part of oxygen-carriers; (2) the weak chamber acid which was mixed
with the nitrous vitriol is concentrated by the hot kiln gases; and (3)
the hot gases themselves are cooled. The acid from the Glover tower is
purified by special treatment--for example, the arsenic may be removed,
after precipitation with sulphuretted hydrogen, in the form of insoluble
arsenic sulphide,--and the purified acid is concentrated by heating in
glass or platinum vessels.
A considerable amount of sulphuric acid is now made by the so-called
"contact process," in which sulphur dioxide and oxygen unite to form
sulphuric acid in presence of a h
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