son, fabrics should be removed from
the bleaching solution as soon as possible, and should then be rinsed
in some solution, such as ammonia, which is capable of neutralizing
the harmful substances; finally the fabric should be thoroughly rinsed
in water in order that all foreign matter may be removed. The reason
home bleaching is so seldom satisfactory is that most amateurs fail to
realize the necessity of immediate neutralization and rinsing, and
allow the fabric to remain too long in the bleaching solution, and
allow it to dry with traces of the bleaching substances present in the
fibers. Material treated in this way is thoroughly bleached, but is at
the same time rotten and worthless. Chloride of lime is frequently
used in laundry work; the clothes are whiter than when cleaned with
soap and simple washing powders, but they soon wear out unless the
precaution has been taken to add an "antichlor" or neutralizer to the
bleaching solution.

220. Commercial Bleaching. In commercial bleaching the material to
be bleached is first moistened with a very weak solution of sulphuric
acid or hydrochloric acid, and is then immersed in the bleaching
powder solution. As the moist material is drawn through the bleaching
solution, the acid on the fabric acts upon the solution and releases
chlorine. The chlorine liberates oxygen from the water. The oxygen in
turn attacks the coloring matter and destroys it.

[Illustration: FIG. 159.--The material to be bleached is drawn through
an acid _a_, then through a bleaching solution _b_, and finally
through a neutralizing solution _c_.]

The bleached material is then immersed in a neutralizing bath and is
finally rinsed thoroughly in water. Strips of cotton or linen many
miles long are drawn by machinery into and out of the various
solutions (Fig. 159), are then passed over pressing rollers, and
emerge snow white, ready to be dyed or to be used as white fabric.

221. Wool and Silk Bleaching. Animal fibers like silk, wool, and
feathers, and some vegetable fibers like straw, cannot be bleached by
means of chlorine, because it attacks not only the coloring matter but
the fiber itself, and leaves it shrunken and inferior. Cotton and
linen fibers, apart from the small amount of coloring matter present
in them, contain nothing but carbon, oxygen, and hydrogen, while
animal fibers contain in addition to these elements some compounds of
nitrogen. The presence of these nitrogen compounds influences