nor are they in any way
so strong as ordinary silk fibre of the same diameter.

Artificial silk can be dyed in the same manner as ordinary silk.

ACTION OF OXIDISING AGENTS ON CELLULOSE OR COTTON

Cellulose resists fairly well the action of weak oxidising agents; still
too prolonged an action of weak oxidising agents has some influence upon
the cotton fibre, and it may be worth while to point out the action of
some bodies having an oxidising effect.

Nitric acid of about 1.15 specific gravity has little action in the
cold, and only slowly on it when heated. The action is one of oxidation,
the cellulose being transformed into a substance known as oxycellulose.
This oxycellulose is white and flocculent. It tends to form gelatinous
hydrates with water, and has a composition corresponding to the formula
C{6}H{10}O{6}. It is soluble in a mixture of nitric and sulphuric
acids, and on diluting this solution with water a tri-nitrate
precipitates out. A weak solution of soda dissolves this oxycellulose
with a yellow colour, while strong sulphuric acid forms a pink
colouration. It is important to note that nitric acid of the strength
given does not convert all the cellulose into oxycellulose, but there
are formed also carbonic and oxalic acids. When cotton is passed into
strong solutions of bleaching powder and of alkaline hypochlorites and
then dried, it is found to be tendered very considerably. This effect of
bleaching powder was first observed some thirteen years ago by George
Witz, who ascribed the tendering of the cotton to the formation of an
oxycellulose. Although the composition of this particular oxycellulose
so formed has not yet been ascertained, there is reason to think that it
differs somewhat from the oxycellulose formed by the action of the weak
nitric acid. A notable property of the oxycellulose now under
consideration is its affinity for the basic coal-tar dyes, which it will
absorb directly. The oxycellulose is soluble in alkaline solutions.

In the ordinary bleaching process there is considerable risk of the
formation of oxycellulose by the employment of the bleaching solutions
of too great a strength, or in allowing the goods to lie too long before
the final washing off. The presence of any oxycellulose in bleached
cotton may be readily determined by immersing it in a weak solution of
Methylene blue, when, if there be any oxycellulose present, the fibre
will take up some of the dye-stuff.

Permangana