The Chemistry of Hat Manufacturing | Page 2

but I will refer you to the interesting and complete work of Dr.
Bowman, On the Structure of the Cotton Fibre. Suffice it to say that in
certain plants and trees the seeds or fruit are surrounded, in the pods in
which they develop, with a downy substance, and that the cotton shrub
belongs to this class of plants. A fibre picked out from the mass of the
downy substance referred to, and examined under the microscope, is
found to be a spirally twisted band; or better, an irregular, more or less
flattened and twisted tube (see Fig. 1). We know it is a tube, because on
taking a thin, narrow slice across a fibre and examining the slice under
the microscope, we can see the hole or perforation up the centre,
forming the axis of the tube (see Fig. 2). Mr. H. de Mosenthal, in an
extremely interesting and valuable paper (see J.S.C.I.,[1] 1904, vol.
xxiii. p. 292), has recently shown that the cuticle of the cotton fibre is
extremely porous, having, in addition to pores, what appear to be
minute stomata, the latter being frequently arranged in oblique rows, as
if they led into oblique lateral channels. A cotton fibre varies from 2·5
to 6 centimetres in length, and in breadth from 0·017 to 0·05 millimetre.
The characteristics mentioned make it very easy to distinguish cotton
from other vegetable or animal fibres. For example, another vegetable
fibre is flax, or linen, and this has a very different appearance under the
microscope (see Fig. 3). It has a bamboo-like, or jointed appearance; its

tubes are not flattened, nor are they twisted. Flax belongs to a class
called the bast fibres, a name given to certain fibres obtained from the
inner bark of different plants. Jute also is a bast fibre. The finer
qualities of it look like flax, but, as we shall see, it is not chemically
identical with cotton, as linen or flax is. Another vegetable fibre,
termed "cotton-silk," from its beautiful, lustrous, silky appearance, has
excited some attention, because it grows freely in the German colony
called the Camaroons, and also on the Gold Coast. This fibre, under the
microscope, differs entirely in appearance from both cotton and flax
fibres. Its fibres resemble straight and thin, smooth, transparent, almost
glassy tubes, with large axial bores; in fact, if wetted in water you can
see the water and air bubbles in the tubes under the microscope. A
more detailed account of "cotton-silk" appears in a paper read by me
before the Society of Chemical Industry in 1886 (see J.S.C.I., 1886, vol.
v. p. 642). Now the substance of the cotton, linen or flax, as well as that
of the cotton-silk fibres, is termed, chemically, cellulose. Raw cotton
consists of cellulose with about 5 per cent. of impurities. This cellulose
is a chemical compound of carbon, hydrogen, and oxygen, and,
according to the relative proportions of these constituents, it has had the
chemical formula C{6}H{10}O_{5} assigned to it. Each letter stands
for an atom of each constituent named, and the numerals tell us the
number of the constituent atoms in the whole compound atom of
cellulose. This cellulose is closely allied in composition to starch,
dextrin, and a form of sugar called glucose. It is possible to convert
cotton rags into this form of sugar--glucose--by treating first with
strong vitriol or sulphuric acid, and then boiling with dilute acid for a
long time. Before we leave these vegetable or cellulose fibres, I will
give you a means of testing them, so as to enable you to distinguish
them broadly from the animal fibres, amongst which are silk, wool, fur,
and hair. A good general test to distinguish a vegetable and an animal
fibre is the following, which is known as Molisch's test: To a very
small quantity, about 0·01 gram, of the well-washed cotton fibre, 1 c.c.
of water is added, then two to three drops of a 15 to 20 per cent.
solution of alpha-naphthol in alcohol, and finally an excess of
concentrated sulphuric acid; on agitating, a deep violet colour is
developed. By using thymol in place of the alpha-naphthol, a red or
scarlet colour is produced. If the fibre were one of an animal nature,

merely a yellow or greenish-yellow coloured solution would result. I
told you, however, that jute is not chemically identical with cotton and
linen. The substance of its fibre has been termed "bastose" by Cross
and Bevan, who have investigated it. It is not identical with ordinary
cellulose, for if we take a little of the jute, soak it in dilute acid, then in
chloride of lime or hypochlorite of soda, and finally pass it through a
bath of sulphite of soda, a beautiful crimson colour develops upon it,
not developed in the case