This historic book may have numerous typos and missing text.
Purchasers can download a free scanned copy of the original book
(without typos) from the publisher. Not indexed. Not illustrated.
1872 Excerpt: ...Moor, in Cumberland, at Lead Hills in Scotland, at
Aix-la-Chapelle, at Tarnowitz in Silesia, in the north-west of
Spain, and in many other places. It sometimes contains more than
two parts of cadmium in the hundred. In Spain, the carbonate of
zinc is found in combination with the hydrated oxide of zinc, so
that the ore contains as much as 57 parts of zinc in the hundred.
Beds of calamine are reported to have been recently found in
Sardinia. The chief English zinc-works are situated in Birmingham
and Bristol, where the ores from the Mendip Hills and Flintshire
are smelted; in Sheffield, where the ore is procured from Alston
Moor; and at Swansea, Wigan, Llanelly, and Wrexham In order to
extract zinc from its ores, advantage is taken of the comparative
facility with which the metal is converted into vapour, since it
boils and distils freely at a temperature estimated at about 19000
F., a bright red heat, somewhat below the melting point of copper.
The ores are calcined so as to obtain the zinc in the form of
oxide, which is then mixed with carbon and distilled, when the
oxygen passes off in combination with the carbon as carbonic oxide
gas, and the zinc is given off in vapour which is condensed again.
The mode in which the operation is carried out differs in different
works, but the principle of the process is always the same.
Calamine is the principal ore treated in this country, and is
sometimes smelted without previous calcination, because
the.carbonic acid which is combined with the oxide of zinc can be
driven off in the smelting process itself; but the calcination or
roasting of blende is indispensable, to enable the oxygen of the
air to convert the zinc into oxide, and to carry off, in the form
of sulphurous acid gas, the sulphur previously in combinatio...
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