l fat. The former is composed of the
potash salts of fatty acids, principally oleic and stearic acids; the
latter of the neutral carbohydrate, cholesterine, with other similar
bodies. The wool perspiration may be removed by a simple washing with
water, and on the Continent forms a valuable source of potash salts,
since the ash after ignition contains 70 to 90 per cent. of potassium
carbonate. The wool fat is insoluble in water, but dissolves readily
in ether, benzene, carbon disulphide, etc.

It is also removed from the wool by a treatment with alkali, and it is
not easy to explain the action in the case, since the wool fat is not
a glyceride, and will not form a soap, but is probably emulsified by
the wool perspiration.

#Chemical Composition of the Pure Fibre.#--The following analyses of
purified and dried wool fibre indicate its percentage composition:--

Mulder. Bowman.
Carbon 50.5 per cent. 50.8 per cent.
Hydrogen 6.8 " 7.2 "
Nitrogen 16.8 " 18.5 "
Oxygen 20.5 " 21.2 "
Sulphur 5.4 " 2.3 "
----- -----
100.0 100.0

It is sometimes stated that wool fibre consists of a definite (p. 008)
substance, keratine, but this view cannot now be admitted, since wool
appears to be composed of a mixture or combination of several very
complex substances. It is possible and even probable that the outer
epidermal scales have a somewhat different composition to the bulk of
the fibre, but whether that is the case or not is not known with any
degree of certainty, this much can be asserted, that wool is not a
simple definite chemical compound.

Sulphur is by far the most variable constituent of wool, sometimes as
little as 1.5 and occasionally as much as 5 per cent. being found. It
appears to be always present in two different forms, one portion being
in very feeble combination and easily removed by alkalies, the
remainder, which, according to Knecht, amounts to about 30 per cent.
of the total sulphur, cannot be removed without complete
disintegration of the fibre. This latter portion does not give a black
coloration with plumbite of soda.

The amount of ash left on incinerating dry wool varies from 1 to 2 per
cent., and some have considered this inorganic matter as an essential
constituent. It consists principally of salts of potassium, calcium
and aluminum, with, of cours