ibres have not
the flattened, twisted appearance of the ripe fibres, but are flatter,
and the central canal is almost obliterated and the fibres are but
little twisted. Dead fibres are thin, brittle and weak.

=Composition of the Cotton Fibres.=--Of all the vegetable textile fibres
cotton is found to have the simplest chemical composition and to be, as
it were, the type substance of all such fibres, the others differing
from it in several respects. When stripped of the comparatively small
quantities of impurities, cotton is found to consist of a substance to
which the name of cellulose has been given.

[Illustration: FIG. 1.--Cotton Fibre.]
[Illustration: FIG. 1A.]

Cellulose is a compound of the three elements, carbon, hydrogen and
oxygen, in the proportions shown in the following analysis:--

Carbon, 44.2 per cent.,
Hydrogen, 6.3 per cent.,
Oxygen, 49.5 per cent.,

which corresponds to the empirical formula C{6}H{10}O{5}, which shows
it to belong to the group of carbo-hydrates, that is, bodies which
contain the hydrogen and oxygen present in them in the proportion in
which they are present in water, namely H{2}O.

Cellulose may be obtained in a pure condition from cotton by treatment
with alkalies, followed by washing, and by treatment with alkaline
hypochlorites, acids, washing and, finally, drying. As thus obtained it
is a white substance having the form of the fibre from which it is
procured, showing a slight lustre, and is slightly translucent. The
specific gravity is 1.5, it being heavier than water. It is
characterised by being very inert, a property of considerable value from
a technical point of view, as enabling the fibres to stand the various
operations of bleaching, dyeing, printing, finishing, etc. Nevertheless,
by suitable means, cellulose can be made to undergo various chemical
decompositions which will be noted in some detail.

Cellulose on exposure to the air will absorb moisture or water. This is
known as hygroscopic moisture, or "water of condition". The amount in
cotton is about 8 per cent., and it has a very important bearing on the
spinning properties of the fibre, as it makes the fibre soft and
elastic, while absolutely dry cotton fibre is stiff, brittle and
non-elastic; hence it is easier to spin and weave cotton in moist
climates or weather than in dry climates or weather. Cotton cellulose is
insoluble in all ordinary solvents, such as water, ether, alcohol,
chloroform, benzene, etc.,