lly
in instrument-making; this use depends upon their electrical properties
of high insulation and low inductive capacity. Hydrated forms of
cellulose, which result from treatment with various reagents, are the
bases of the following industries: vegetable parchment results from the
action of sulphuric acid upon cellulose (cotton) in the form of paper,
followed by that of water, which precipitates the partially
colloidalized cellulose. This industry is carried out on "continuous"
machinery, the cellulose, in the form of paper, being treated in rolls.
Vulcanized fibre is produced by similar processes, as for instance by
treating paper with zinc chloride solvents and cementing together a
number of sheets when in the colloidal hydrated state; the goods are
exhaustively washed to remove, last traces of soluble electrolytes; this
is necessary, as the product is used for electrical insulation. The
solvent action of cupro-ammonium is used in treating cellulose goods,
cotton and paper, the action being allowed to proceed sufficiently to
attack the constituent fibres and convert them into colloidal
cupro-ammonium compounds, which are then dried, producing a
characteristic green-coloured finish of colloidal cellulose and
rendering the goods impervious to water. The important industry of
mercerization has been mentioned above; this is carried out on both
yarns and cloth of cotton goods chiefly composed of Egyptian cottons. A
high lustrous finish is produced, giving the goods very much the
appearance of silk.

Of special importance are the more recent developments in the production
of artificial fibres of all dimensions, by spinning or drawing the
solutions of cellulose or derivatives. Three such processes are in
course of evolution, (1) The first is based on the nitrates of cellulose
which are dissolved in ether-alcohol, and spun through fine glass jets
into air or water, the unit threads being afterwards twisted together to
constitute the thread used for weaving (process of Chardonnet and
Lehner). These processes were developed in the period 1883 to 1897, at
which later date they had assumed serious industrial proportions. (2)
The cupro-ammonium solution of cellulose is similarly employed, the
solution being spun or drawn into a strong acid bath which instantly
regenerates cellulose hydrate in continuous length. (3) Still more
recently the "viscose" solution of cellulose, i.e. of the cellulose
xanthogenic acid, has been perfected