Celluloid, or PARKESINE. This substance was first made by Mr A. Parkes of Birmingham in 1855 or 1856. It chiefly consists of a dried solution of gun-cotton (pyroxilin), or of what is nearly the same thing, and oil. A variety of it can be made with pyroxilin and camphor. It resembles ivory, horn, tortoiseshell, and hardened india-rubber, as regards certain properties.
The pyroxilin is prepared by treating Cellulose (q.v.) from such vegetable materials as cotton or flax waste, rags, paper-makers' half-stuff, or paper itself, with a mixture of one part of strong nitric acid and four parts of strong sulphuric acid. It is convenient to call the product so obtained pyroxilin, although the two things are not quite identical. The distillate obtained by distilling wood naphtha with chloride of lime is used as a solvent for the pyroxilin, but other solvents, such as nitrobenzol or aniline, and some camphor are added with advantage. When the excess of solvent is removed from the pyroxilin, it is mixed with a considerable quantity of castor-oil or cotton-seed oil, and made into a dough or paste between heated rollers. For a hard compound the quantity of oil should be less than the pyroxilin, for a soft one it should be greater. Chloride of sulphur is sometimes added to the oil. When articles made of celluloid are in a partially manufactured state, they are soaked in bisulphide of carbon or chloride of lime to remove any trace of solvent, which would render them apt to shrink if allowed to remain. Celluloid is of a somewhat combustible nature unless the substances used to colour it are such as will neutralise this, or unless some non-combustible chemical, tungstate of soda for example, is added to it.
Properties and Uses.—Celluloid has many valuable properties. It is buff or pale brown in colour, but it can be made as white as ivory, which it much resembles, or manufactured in a transparent state. It can be moulded or pressed into any form, and turned, planed, or carved. Neither the atmosphere nor water affects it. It is elastic and can be united by its own cement. In a plastic condition celluloid can be spread on textile fabrics, or it may be made as hard as ivory, for which it is largely used as a substitute. Billiard-balls, piano-keys, and combs are made of it, the latter two articles extensively. It can be coloured to represent amber, tortoiseshell, or malachite. In imitation of red coral it has been a good deal used for jewelry. Like vulcanite, which it excels in durability but exceeds in price, it has very numerous applications. We need only mention umbrella-handles, brush-backs, knife-handles, buttons, napkin-rings, card-cases, thimbles, and dolls. It is useful for optical instruments, for cases for artificial teeth, and for some surgical instruments. One special application of it is for shirt fronts and collars. It is used for very pretty imitations of ivory, amber, tortoiseshell, coral, malachite, &c. Some important developments in the manufacture and application are due to J. W. Hyatt, of Newark, U.S.