The new Northwest. [volume] (Portland, Or.) 1871-1887, 1873-08-15
How Alum is Obtained.

In some portions of Europe alum stone,
a grayish colored mineral, Is found In
large quantities, from which the best
alum OF commerce Is procured; in Italy
this stone is obtained from quarries by
blasting, 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 parallel piles of these stones, ar
ranged in regularly formed layers, on
each side of which, and In close proxim-
ity, channels are exeavated and dlled
with water. A gentle heat Is then ap-
piled, and the water sprinkled over the
heaps at frequent Intervals. BY this
treatment the stones soon commence to
pulveriZe, but the moistening Is coz
tinued for several weeks, as II facilitates
the separation of their constituent ele-
ments. When completely pulysrized,
the powder is thoroughly boiled in ves-
sells especially prepared for this purpose.
This process causes a subsidence OF
earthly ingredients, and an evaporation
of all volatile foreign substances. The
liquid Is then Withdrawn into other
vessels, and allowed to remain undis-
turbed until the alum appears in the
form of crystals, which is usually the
case in the course of few days. This
is termed Roman alum, and is regarded
as the most valuable variety in the mar
ket, because possessing fewer impurities
than any other. 1t can be ereadily recog-
niZed by the auburn tint seen on the
surface, which is impaired it by the
presence of minute particles of the sui
phate of iron.
Another variety of alum is manufac-
tured from alum slate, a species OF
sandstone containing a large quantity
of clay, which Is extensively dissemi-
mated 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 a certain
amount of heat and moisture. AT
Whitby, where the most extensive
manufactures of Europe are located,
these masses are often built to a height
of one hundred feet square. Owing
| to the composition of these states,
twelve months, aud often more, are
| required for the burning process.
After an artificial fire has been cOntin-
ued for several weeks, no additional food
is necessary, as the chemical changes in
the ingredients will furnish sufficient
material for combustion. When thor.
Oughly pulverized by this process the
powder is placed in large Vessels of wa
ter, where the soluble salts they contain
are washed out, after which the liuuor
is boiled, and, for the purpose of elfmi-
! mating all impurities, condensed by the
J agency of heat into a powerful solution
of copperas and the sulphate of ammo
. mia or basic alum. This liquor, thus
condensed, is then conveyed into large
tanks, where the iron is chemically sep
arated and a suitable alkali added lthe
basic alum not possessing the quality of
crystallization), which causes the for
nation of crystals OH 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. Ii is estimated that
6l4 tons of alum slate are required to
one ton of slum.-N y Mercantile Jour
nal.