668 ( RKATIVK (^HEMISTRY and other decorative fabrics. It is mothproof and takes readily to antimildevving and fire-retardant preparations. A new continuous process for the production of rayon was started in 1940 in a huge plant, built after six years of research, at a cost of $11,500,000, by the Industrial Rayon Corporation at Painesville, Ohio; it represents one of the outstanding chemical engineering achievements of our generation. In this fourteen-acre, windowless, air-conditioned plant, 371,000 glass blocks were used. This is the first plant in which the rayon threads are formed, bleached, shrunk, prepared, dried, and twisted before being wound in bobbins for shipment. 3. Esters. Cellulose, when treated with a mixture of sulfuric and nitric acids, forms compounds with the nitric acid which are called "esters." Partially nitrated cellulose is called "pyroxylin." It dissolves in a mixture of alcohol and ether and other solvents to produce liquid court plaster, fingernail polish, and household cements. Photographic films are made from pyroxylin because it serves as an excellent base for the photographic emulsion. When heated with camphor and a little alcohol, pyroxylin produces a tough, doughlike, plastic mass which can be easily shaped. The products obtained by the evaporation of the alcohol in this plastic mass are sold under such trade names as "Celluloid," "Xylonite," and "Pyralin." Such nitrocellulose plastics may be obtained in practically every shade and hue, in beautiful transparent, translucent, mottled, opaque, and pearl efTects. They are employed in the manufacture of such diversified products as toiletware, fountain-pen barrels, radio dials, optical frames, and buttons. Incidentally, camphor, which originally came from the camphor trees in Formosa, is now synthesized from turpentine obtained from our southern pines, thus breaking what was once a Japanese monopoly. As recently as 1920, refined imported natural camphor reached $3.55 a pound; today refined synthetic camphor, medicinal grade, is selling for around 60 cents a pound, while the technical grade, used in plastics and photographic film, sells for only about 35 cents a pound. The importance of synthetic camphor can be appreciated when one knows that the manufacture of photographic film alone requires more than half a million pounds a year. Lacquers are solutions of pyroxylin, with or without dyes or pigments. Their discovery revolutionized the painting industry and greatly aided in various manufacturing processes; for example, an automobile can now be finished with lacquer in a few hours, whereas it formerly required as much as three weeks for the older varnishes and enamels to dry by the slow processes of oxidation or baking.
"BETTER THINGS" FROM CELLULOSE 669 Just as lacquers have partially displaced oxidizing oil products for finishes, various new fabrics are replacing the older materials produced by the oxidation of linseed and other drying oils. Oilcloth is made by coating a cotton base with linseed oil containing the desired pigment. Linoleum is a somewhat similar product to which has been added ground cork. Today canvas is coated or impregnated with pyroxylin solutions containing materials to impart flexibility or color and to produce durable fabrics, which are sometimes called "artificial leather" or "leather cloth." Frequently they replace leather and are treated so as to resemble leather. For many uses, such as book bindings, they are not only cheaper than, but also superior to, leather. When cellulose is further nitrated, a somewhat different cellulose nitrate, called guncotton, is obtained. Guncotton, though a high explosive, is too bulky, because it retains the original form of the cotton from which it was made ; and it is too dangerous to use because of its sensitiveness to shock. In 1867 a Swedish chemist, Alfred Nobel, discovered that guncotton would dissolve in warm nitroglycerine, which in itself is an excellent explosive but difficult to handle because of its liquid state and too great sensitivity to shocks. It was found that the resulting mixture, containing a little acetone and vaseline, was less sensitive and could be used as a propellant powder. One such powder is the British "Cordite." While smokeless powder may be made in this way, it is usually made in the United States simply by "colloiding" the guncotton with ether and alcohol to form a homogeneous and amorphous dough. This dough is then forced through dies somewhat similar to a macaroni machine, but which, in the case of cannon powder for example, have seven axial perforations made in the cord. The cord is then cut off into short lengths two or three times its diameter. These are then dried to expel the solvent. Alfred Nobel also invented dynamite, which is a mixture of nitroglycerine and sawdust or infusorial earth. It is interesting to note that Nobel left his money, made from the invention of these powerful explosives, to establish five world-famous prizes in peace, literature, medicine and physiology, physics, and chemistry. Rayon dresses could be made from pyroxylin, but they would be very dangerous to wear because, once ignited, they would burn very rapidly. Methods have been found to remove the nitrate radicals after the cellulose nitrate threads are formed so as to convert them into cellulose, which is no more inflammable than cotton or other types of rayon. This process is one of the less important rayon processes now in use.