Читать книгу Henley's Formulas, Recipes and Processes (Applied Chemistry) - Various - Страница 650

—Calcium carbide is readily attacked by the air and the moisture contained in the generators and consequently decomposes during the storing, with formation of acetylene gas. Aside from the loss, this decomposition is also attended with dangers. One of the oldest methods of preservation is the saturation of the carbide with petroleum. In using such carbide a layer of petroleum forms on the surface of the water in the generator, which prevents the water from evaporating, thus limiting the subsequent generation of acetylene from the remaining carbide. Instead of petroleum many other substances have been proposed which answer the purpose equally well, e.g., toluol, oils, solid bodies, which previously have to be liquefied, such as stearine, paraffine, rosin, etc.

Of a different nature is a medium offered by Létang of Paris. He employs sugar or saccharine bodies to which he adds, if necessary, a little petroleum, turpentine, vaseline, or varnish of any kind, as well as chalk, limestone, talc, sulphur, or sand. The carbide is coated with this mixture. The saccharine substances dissolve in the generating water, and also have a dissolving action on the slaked lime, which is formed by the decomposition of the carbide which admits of its easy removal.

According to another process carbide is put on the market in such a shape that, without weighing, merely by counting or measuring one is in a position to use equivalent quantities for every charge. Gearing casts molten carbide in the shape of bars, and pours a layer of gelatin, glue, and water soluble varnish over the carbide bars. Others make shells containing a certain quantity of reduced carbide. For this ordinary and varnished pasteboard, wax paper, tinfoil, thin sheet zinc, and similar substances may be used which ward off atmospheric moisture, thus protecting the carbide from premature decomposition. Before use, the cartridge-like shell is pierced or cut open, so that the water can get at the contents. The more or less reduced carbide is filled in the shell, either without any admixture or united into a compact mass by a binding agent, such as colophony, pitch, tar, sand, etc.