The Democratic advocate. [volume] (Westminster, Md.) 1865-1972, 1873-06-21
Our @lio,
How Alum is Obtained.


In some portions of Europe Alum stone,
grayish eolored mineral, is fonnd in
large quantities, from which the best alum
Of commerce is procured; in Italy this
stone is obtained from quarries by blast
ing, and, when exposed for a short time to
moist atmosphere, becomes friable and
eventually falls to pieces.
The first process in the manufacture of
this variety of alum is the erection Of par
allel piles Of these stones, arranged in reg
ularly formed layers, on each side of
which, and in close proximity, channels are
excavated and filed with water. A gentle
heat is then applied, and the water sprink-
led over the heaps at frequent intervals
By this treatment the stones commence to
pulyerize, but the moistening is continued
for several weeks, as it facilitates the sep
aration of their constituent elements.
When completely pulverised the powder is
thoroughly boiled in vessels specially pre-
pared for this purpose. This process
causes subsidence of earthly ingredients,
and an evaporation Of all volatile foreign
substances The liquid is then withdrawn
into other vessels, and allowed to remain
undisturbed until the alum appears in the
form of crystals, which is usually the case
in the course Of a few days. This is
termed Roman alum, and is regarded as
the most valuable variety in the market,
because possessing fewer impurities than
any other. 1t can be readily recognized
by the auburn tint seen on the surface,
which is impaired to it by the presence of
minute particles of the sulphate Of iron.
Another variety of alum is manufactured
from alum slate, species Of sandstone
containing a large quantity of clay, which
is extensively disseminated throughout
different portions of the United States and
Canada. In its preparation, the states, like
the alum rocks, are arranged in regularly
formed masses and subjected to certain
amount of heat and moisture. At Whitby,
where the most extensive manufactures Of
Europe arc located, these masses are often
built to u height Of one hundred feet
square. Owing to the composition Of
these states, twelve months, and often more,
are required for the burning process.
After an artificial FIRE has been continued
for several weeks, no additional food is
necessary, as the chemical changes in the
ingredient will furnish sufficient material
for combustion. When thoroughly pul.
verised by this process the powder is placed
in large vessels Of water, where the soluble
salts they contain are washed out, after
which the liquor is boiled, and, for the
purpose of eliminating all impurities, con.
densed by the agency of heat into pow.
erful solution of copperas and the sui phate
of ammonia or basic alum This liqour
thus condensed, is then conveyed into large
tanks, where the iron is chemically sepa.
rated and suitable alkali added 1.-THE basic
alum not possessing the property of crys.
tallization,) which causes the formation Of
crystals on the sides of the tanks. These
are again dissolved, and the solution placed
in casks, around the sides of which, in a
short time, the alum crystals are reformed
and these when they become free from
moisture, are ready for market. 1t is es-
timated that Ga tons of alum slate are re.
quired to one ton Of alum.-N. y .Mer-
cantik Journal