of
space, and these differences exist at one and the same points of time." It
is possible with this plant to produce the full product of nitric acid of
a gravity of 1.500, or to obtain the acid of varying strengths from the
different still-heads. One of these stills, capable of producing about 4
tons of nitric acid per week, weighs less than 2 tons. It is claimed that
there is by their use a saving of more than two-thirds in fuel, and four-
fifths in condensing plant. Further particulars and illustrations will be
found in Mr Prentice's paper (_Journal of the Society of Chemical
Industry_, 1894, p. 323).

CHAPTER III.

_NITRO-CELLULOSE, &c._

Cellulose Properties--Discovery of Gun-Cotton--Properties of Gun-Cotton--
Varieties of Soluble and Insoluble Gun-Cottons--Manufacture of Gun-Cotton--
Dipping and Steeping--Whirling out the Acid--Washing--Boiling--Pulping--
Compressing--The Waltham Abbey Process--Le Bouchet Process--Granulation of
Gun-Cotton--Collodion-Cotton--Manufacture--Acid Mixture used--Cotton used,
&c.--Nitrated Gun-Cotton--Tonite--Dangers in Manufacture of Gun-Cotton--
Trench's Fire-Extinguishing Compound--Uses of Collodion-Cotton--Celluloid--
Manufacture, &c.--Nitro-Starch, Nitro-Jute, and Nitro-Mannite.

~The Nitro-Celluloses.~--The substance known as cellulose forms the
groundwork of vegetable tissues. The cellulose of the woody parts of
plants was at one time supposed to be a distinct body, and was called
lignine, but they are now regarded as identical. The formula of cellulose
is (C_{6}H_{10}O_{6})_{X}, and it is generally assumed that the molecular
formula must be represented by a multiple of the empirical formula,
C_{12}H_{20}O_{10} being often regarded as the minimum. The assumption is
based on the existence of a penta-nitrate and the insoluble and colloidal
nature of cellulose. Green (_Zeit. Farb. Text. Ind._, 1904, 3, 97)
considers these reasons insufficient, and prefers to employ the single
formula C_{6}H_{10}O_{5}. Cellulose can be extracted in the pure state,
from young and tender portions of plants by first crushing them, to
rupture the cells, and then extracting with dilute hydrochloric acid,
water, alcohol, and ether in succession, until none of these solvents
remove anything more. Fine paper or cotton wool yield very nearly pure
cellulose by similar treatment.

Cellulose is a colourless, transparent mass, absolutely insoluble in
water, alcohol, or ether. It is, however, soluble i