CELLULOID, an artificial substance in vented in its modern form by the brothers Hyatt of Newark, N. J., in 1869 (U. S. Letters Patent No. 88,634) extensively used as a sub stitute for ivory, bone, hard rubber, coral, etc., having a close resemblance to these substances in hardness, elasticity and finish. It is com posed of the lower nitrates • of cellulose, gela tinized in a solution of camphor in methyl or ethyl alcohol. The nitrates of cellulose are usually prepared by subjecting tissue paper to the action of a bath of mixed nitric and sul phuric acids for 20 minutes at a temperature of at least 30° C. The resulting substance is dried by blotting or by the use of alcohol, and incor porated by heat or mixture with alcohol, cam phor and any pigments or fillers that may be used. The dough-like mass then resulting is worked into form by various means, and these seasoned by being kept from one to six weeks at 30° C. to evaporate the alcohol. Urea is
often added as a stabilizer, and various sorts of dyes or pigments may be used. Celluloid is plastic at 75'. It is very inflammable. It is used for films for cameras and moving pictures, but on account of its excessive inflammability is coming to be replaced by preparations of the acetic-acid ester of cellulose. Celluloid var nishes for lacquering on metal are prepared from various pyroxylin preparations and pig ments. Consult Bockman, (Celluloid) (London 1907); Ertet, (Die Celluloid Industrie> (1909) ; Lehner,