ere already free.

Even with liquid bleaching the bleach is not any more perfect than it
is with the gas bleaching; the colour is liable to come back again on
being washed with soap or alkali, although there is a freedom from the
defect of yellow stains being produced.

Goods properly bleached will stand exposure to air for some
considerable time, but those imperfectly bleached exhibit a tendency
to regain their yellow colour on exposure to air. One fault which is
sometimes met with in sulphur bleaching is a want of softness in (p. 034)
the wool, the process seeming to render the fibre harsh.

Washing in a little weak soft soap or in weak soda will remedy this
and restore the suppleness of the wool; at the same time care must be
taken that the alkaline treatment is not too strong, or otherwise the
bleaching effect of the sulphur will be neutralised as pointed out
above.

#Bleaching Wool by Peroxide of Hydrogen.#--During recent years there has
come into use for bleaching the animal fibres peroxide of hydrogen,
or, as the French call it, oxygenated water. This body is a near
relation to water, being composed of the same two elements, oxygen and
hydrogen; in different proportions in water these elements are
combined in the proportion of 1 part of hydrogen to 8 parts of oxygen,
while in the peroxide the proportions are 1 of hydrogen to 16 of
oxygen. These proportions are by weight, and are expressed by the
chemical formulae for water H_{2}O, and for hydrogen peroxide
H_{2}O_{2}. Water, as is well known, is a very stable body, and
although it can be decomposed, yet it requires some considerable power
to effect it. Now the extra quantity of oxygen which may be considered
to have been introduced into water to convert it into peroxide has
also introduced an element of instability, the extra quantity of
oxygen being ever ready to combine with some other body for which it
has a greater affinity than for the water. This property can be
utilised in the bleaching industry with great advantage, true
bleaching being essentially a process of oxidation. The colouring
matter of the fibre, which has to be destroyed so that the fibre shall
appear white, is best destroyed by oxidation, but the process must not
be carried out too strongly, otherwise the oxidation will not be
confined to the colouring matter, but will extend to the fibre itself
and disintegrate it, with the result that the fibre will become
tendered and be rendered use