s of
solvents, like carbon bisulphide, benzol, petroleum spirit, etc. Such
processes are in a sense rather more scientific than the alkali
processes, for whereas in the latter the grease, etc., of the wool and
the oil used in batching it are practically lost for further use, and
therefore wasted, being thrown away very often, although they may be
partially recovered from the used scouring liquors, in the solvent
processes the grease and oil may be recovered for future use for some
purpose or other.

The great objection to these processes is the danger that attends
their use, owing to the inflammable character of the solvents. Several
other objections may be raised, some of which are mechanical, and due
to the want of proper machinery for carrying out the processes. There
are many ways in which solvents may be applied, some are the subject
of patents. It is not possible to describe the details of all these,
but two of the most recent will be mentioned.

In Singer's process, which was described in detail by Mr. Watson Smith
some time ago before the Society of Dyers and Colourists, carbon
bisulphide is used. The raw wool is placed between two endless bands
of wire, and it is carried through a series of troughs containing
bisulphide of carbon; during its passage through the troughs the
solvent takes out the grease, and loosens the other constituents of
the wool. After going through the bisulphide the wool is dried and
passed through water which completes the process. The carbon
bisulphide that has been used is placed in steam-heated stills,
distilled off from the grease, condensed in suitable condensers, and
used over again. In this process, with care, there is very little loss
of solvent. The grease which is recovered can be used for various
purposes, one of which is the manufacture of ointments, pomades, etc.
The disadvantages of bisulphide are: (1) It tends after some time (p. 025)
to cause the wool to acquire a yellow cast, due to the free
sulphur which it contains, and which being left in the wool gradually
causes it to turn yellow. By using redistilled bisulphide this defect
may be avoided. (2) Another defect is the evil odour of the solvent.
This, however, is less with redistilled bisulphide than with the
ordinary quality, and with suitable apparatus is not insuperable. (3)
Another defect is the volatility and inflammability of carbon
bisulphide. On the other hand, bisulphide possesses the very great
advantage of