n the wool fibre, leaving the latter in such a
condition that by washing with water the rest of the impurities in the
wool can be extracted. By distilling off and recondensing the solvent
can be recovered for future use, while the wool fat can also be
obtained in a condition to use for various purposes. This is rather a
more scientific method than the old one, but it has not as yet come
into extensive use.

#Wool Scouring. Old Methods.#--In the early days of wool scouring (p. 017)
this operation was done in a very primitive fashion, generally in a
few tubs, which could be heated by steam or otherwise, and in which
wool was worked by means of hand forks. These primitive processes are
still in use in some small works, especially where the wool is dyed in
the loose condition, but in all the large works machinery has been
adopted, which machinery has been brought to a high state of
perfection, and does its work very well, and without much attendant
manual labour.

The alkaline substances used in this process of scouring demand some
notice. These comprise soda ash, soda crystals, caustic soda, silicate
of soda, potash, caustic potash, soaps of various kinds, stale urine,
ammoniacal compounds. Which of these may be used in any particular
case depends upon a variety of reasons. Potash is the best alkaline
agent to use. It agrees better with the fibre than any other, leaving
it soft and elastic. Ammonia is the next best, but it does not take
out the grease as well as the potash. Soda does not suit as well as
potash, as it has a tendency to leave the fibre harsh in feel and
somewhat brittle, yet on account of its being so much cheaper it is
the most largely used. The use of silicate of soda cannot be
recommended, as it has a great tendency to leave the fibre hard, which
may be ascribed to the deposition of silica on the fibre.

The caustic alkalies cannot be used as they have too solvent an action
on the fibre. The carbonates, therefore, in the form of soda ash or
potash, or pearl ash, are used, or better still, soap is used as it
has a greater solvent action on the fatty matter of the wool than have
the alkalies, and in this respect a potash soap is better than a soda
soap.

The character of the wool determines the alkali to be used; fine,
long-stapled wools, which are usually very free from grease in excess,
should always be treated with potash, or a potash soap, which will (p. 018)
remove the whole of the grease from the