CELLULOID, PARKESINE, or XYLONITE. (Fn. and GER Celluloid.) "Celluloid " is decidedly the most convenient name for this product, as it is the one in general use. It consists virtually of vegetable fibre, treated with a mixture of nitric and sulphuric acids, and which, for want of a better term, may be called " pyroxyline," though it is not identical with that compound ; this is dissolved in a suitable solvent, and afterwards dried. The product is a light yellowish-brown coloured body, which can be carved, planed, turned, sawn, stamped, or polished, and made either opaque or transparent. It may be made as hard as ivory, which it closely resembles, but is always elastic, and may be moulded into any form. It can be spread on textile fabrics, &c., and, by placing different coloured layers alternately, and rolling them together while in a plastic condition, any desired marbled or granular effects may be produced. It is easily coloured any tint, and, as the colour permeates the whole mass, it is ioeffaceable. It is plastic and malleable at 125° (257° F.), and decomposes suddenly, without taking fire, but with evolution of reddish fumes, at 140° (284° F.). It is non-explosive, and burns only when in direct contact with a flame. When pure, it is inoclorous, and does not become electric by friction. An important property is that it can be united by means of its own solvent or cement ; and no waste is entailed in its use, as all scraps can be worked up again.
The manufacture may be divided into two distinct stages : 1. The production of the so-called " pyroxyline " ; 2. The treatment of this compound with solvents, in order to make it plastic, and give it other desired qualities. The first stage of the process suffers but little variation. A convenient quantity of cellulose or woody fibre, such as disintegrated cotton waste, paper, &c., is fed into an open vessel called a " converter," and treated with an acid mixture composed of 1 part of nitric acid, sp. gr. 1.420 and 4 to 5 parts of anlphuric acid, sp. gr. 1.845, mixed in a separate
vessel, and kept as cool as possible. The acid mixtureis pumped or forced up into the converter, while the fibrous substance, previously placed in a hopper over the converter, falls gradually into it by an opening in the top. The charging of the cotton into the converter occupies about ten minutes, and at the end of twenty to thirty minutes at moat, it is chemically- converted into the so-called pyroxyline, or nitre-cellulose. This, together with the excess of acids adhering, is then allowed to fall through an opening in the bottom of the converter, and is caught in a large box provided with a false bottom of perforated iron, or wire gauze, at about 6 in. above the real bottom. On this, the wet mass remains for an hour, to admit of the excess of acids draining away as far as possible ; the still remaining impregnations of acid are then expressed by placing the pyroxyline in a cylinder with a perforated bottom, and subjecting it to hydraulic pressure. The result is a hard cylinder of pyroxyline, containing about 5 te 20 per cent. of the acid mixture, in which state it ia stored for future use. When required, the cylinders of pyroxyline are torn into dust by special machinery, such as that employed for grinding paper pulp, and the disintegrated mass falls into a large tank, where it is well washed with water, te remove the last traces of acid. It is then again placed in the cylinders with perforated bottoms, and pressed to remove the water, leaving in only 5 to 20 per cent. The solid cylinders of soluble pyroxyline are again broken up in the disintegrating maChine, preparatory for the treatment with solvents, which forms the second stage of the manu facture.
This is performed in a variety of ways, chiefly according to the ulterior applioations for which the product is intended, and differing less in the apparatus employed than in the ingredients and proportions of the dissolving agents.