e, sulphur.

The chemical composition of the wool fibre is evidently of a most
complicated nature; judging from its behaviour in dyeing it is evident
that it may contain two bodies, one of a basic character which enables
it to combine with the azo and acid series of dyes, the other possessing
acid characters enabling it to combine with the basic dyes of the magenta
and auramine type. Dr. Knecht has isolated from the wool fibre by
extraction with alkalies and precipitation with acids a substance to
which the name of lanuginic acid has been given. It is soluble in hot
water, precipitates both acid and basic colouring matters in the form
of coloured lakes. It yields precipitates with alum, stannous (p. 009)
chloride, chrome alum, silver nitrate, iron salts, copper sulphate. It
appears to be an albuminoid body. From its behaviour with the dyes,
and with tannic acid and metallic salts, it would appear that lanuginic
acid contains both acidic and basic groups. It contains all the
elements, carbon, hydrogen, oxygen, nitrogen and sulphur, found in
wool.

If wool is dyed in a dilute solution of Magenta (hydrochloride of
rosaniline), the whole of the base (rosaniline) is taken up, and the
whole of the acid (HCl) left in the bath, not, however, in the free
state, but probably as NH_{4}Cl, the ammonia being derived from the
wool itself. A further proof of the acid nature of lanuginic acid is
that wool may be dyed a fine magenta colour in a colourless solution
of rosaniline base; for since rosaniline base is colourless, and it
only forms a colour when combined with acids, the fibre has evidently
acted the part of an acid in the combination.

#Chemical Properties. Action of Alkalies.#--Alkalies have a powerful
action on wool, varying, of course, with the nature of the alkali,
strength of solution and temperature at which the action takes place.

An ammoniacal solution of copper hydroxide (Schweizer's reagent), has
comparatively little action in the cold, but when hot it dissolves
wool fairly readily.

The caustic alkalies; sodium hydroxide, NaOH, or potassium hydroxide
KOH, have a most deleterious action on wool. Even when very dilute and
used in the cold they act destructively, and leave the fibre with a
harsh feel and very tender, they cannot therefore be used for scouring
or cleansing wool. Hot solutions, even if weak, have a solvent action
on the wool fibre, producing a liquid of a soapy character from which
the wool i