in turn are placed in hydraulic presses, iron plates being
placed between the bags. Pressure is applied for about eight minutes,
until, as is supposed, all the oil is pressed out, leaving a hard cake,
known to the trade as oil-cake, or linseed-cake.

The product of these various processes is known as "raw" oil, a
considerable portion of which is sold without further labour being
expended upon it. There is, however, a demand for "boiled" oil, for
certain purposes where greater drying properties are needed. To supply
this want oil is placed in large kettles, holding from five hundred to
one thousand gallons, where it is heated to a temperature of about 500
degrees, being stirred continually. This process, when large kettles are
used, requires nearly the entire day. While the boiling process is going
on, oxide of manganese is added, which helps to give the boiled oil
better drying properties. A considerable portion of the oil is bleached,
for the use of manufacturers of white paints.

=Venice Turpentine.=--This is obtained from the larch, and is said to be
contained in peculiar sacs in the upper part of the stem, and to be
obtained by puncturing them. It is a ropy liquid, colourless or brownish
green, having a somewhat unpleasant odour and bitter taste.

=Oil of Turpentine= is the most plentiful and useful of oils. It is
obtained in America from a species of pine very plentiful in the
Carolinas, Georgia, and Alabama, known as the long-leaved pine (_pinus
Australis_), and found only where the original forest has not been
removed.

=Methylated Spirits.=--The methylated spirit of commerce usually
consists of the ordinary mixed grain, or "plain" spirit, as produced by
the large distillers in London and elsewhere, with which are blended,
by simply mixing in various proportions, one part vegetable naphtha and
three parts spirits of wine. The mixing takes place in presence of a
revenue officer, and the spirits so "methylated" are allowed to be used
duty free. The revenue authorities consider the admixture of naphtha,
having so pungent and disagreeable a smell, a sufficient security
against its sale and consumption as a beverage. No process has yet been
discovered of getting rid of this odour. It is illegal for druggists to
use it in the preparation of medicinal tinctures, unless they are for
external use.

PRINTED BY WILLIAM CLOWES AND SONS, LIMITED, LONDON AND BECCLES.

CROSBY LOCKWOOD & SON'S

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