The temperature of the scouring liquors should be about 100 deg. F.,
certainly not more than 120 deg. F., high temperatures are very liable to
bring about felting, while tending to increase the harshness of the
wool, particularly when soda is the agent used. By this method all the
wool fat, suint, etc., of the wool find their way into the soap
liquors. These were formerly thrown away, but they are generally
treated with acid and the fat of the soap and wool recovered, under
the name of wool grease or Yorkshire grease. (_Vide_ G. H. Hurst, (p. 023)
"Yorkshire Grease," _Jour. Soc. Chem. Ind._, February, 1889.)

The wool fat consists largely of a peculiar fat-like body known as
cholesterine. This, however, is unsaponifiable, and cannot be made
into soap; at the same time when it gets into, as it does, the
recovered wool grease it spoils the latter for soap-making purposes.

Cholesterine has some properties which make it valuable for other
purposes; it is a stable body not prone to decomposition, it is
capable of absorbing a large quantity of water, and it is on these
accounts useful for medicinal purposes in the production of ointments,
and it might be useful in candle-making. When it gets into recovered
grease it cannot be extracted from it in an economical manner. The
wool suint consists largely of the potash soaps of oleic and stearic
acids. These two fatty acids find their way into the recovered wool
grease but the potash salts are lost, while they would be valuable for
various purposes if they could be recovered.

Another form of wool-washing machine has a frame carrying a number of
forks arranged transversely to the machine. The forks are by suitable
gearing given a motion which consists of the following cycle of
movements. The forks are driven forwards in the trough of the machine,
carrying the wool along with them, they are then lifted out, carried
back, and again allowed to drop into the machine, when they are ready
to go forward again. Thus the forks continually push the wool from one
end of the machine to the other.

It is a common plan to have three machines placed end to end, so that
the wool passes from one to the other; in a set of this kind the first
machine should have a capacity of 1,500 gallons or thereabouts, the
second 1,000 gallons, and the third 750 gallons.

#Wool Scouring by Solvents.#--Of late years processes have been (p. 024)
invented for the scouring of wool, either raw or spun by mean