OF THE METALLIC CARBIDES. 1 3 



calcium alloy by heating with carbon. Wohler gave some of the proper- 

 ties of the carbide which resulted. In 1893 Travers recorded another 

 method of preparing calcium carbide, and in the following year Moissan 

 produced it in his electric furnace, both from CaCO.^ and from CaO heated 

 with sugar carbon. About the same time the Willson Aluminum Com- 

 pany, in this country, while experimenting upon the reduction of the alkali 

 earths by means of carbon, found that carbide of calcium was formed, 

 although when first produced the compound was not recognized by them, 

 but was considered as a waste product. As soon as its properties were 

 learned, Willson took out patents for its production in this country. BuUier 

 holds a German patent for the production of Ca-, Ba-, and Sr-carbides, 

 although the method patented #s said to be of Moissan's discovery. The 

 carbides of calcium and silicon seem thus far to be the only carbides of 

 commercial value in themselves. The value of calcium carbide lies in 

 its ready decomposition with water, yielding nearly pure acetylene gas, 

 which under proper conditions is unexcelled as an illuminating gas. 

 When made upon a commercial scale, calcium carbide is produced from 

 lime and coke. The cost of production is still rather high, and the chances 

 of acetylene gas being generally introduced for lighting purposes in the 

 immediate future are not very bright. In time the necessary improve- 

 ments may be made which will do away with present difficulties. The 

 cost of the electric power is the chief obstacle now. 



CaCa forms in opaque, brownish-red crystals, sp. gr. 2.22. It is quite 

 insoluble in most of the ordinary solvents in the cold. Dry hydrogen 

 is without action in the cold and seems to be without effect even when hot 

 upon the pure calcium carbide. The commercial article may contain 

 tarry products which a stream of dry hydrogen will drive out. Air acts 

 in about the same way as hydrogen. At a very high temperature a 

 sample, submitted to the action ef a stream of oxygen, glows and is partly 

 oxidized. 



HCl (gas) decomposes it when hot. CI and Br at even moderate 

 temperatures cause the sample to glow brightly, to swell up, and then tuse 

 together. Very slight action in the cold when treated with H0SO4, but 

 by heating the action is increased and a gas is evolved which burns with 

 a luminous flame. 



W^ith a mixture of H,,S04 and K^CroO^ calcium carbide reacts violently, 

 vigorous oxidation taking place. Little or no CoHo is evolved in the 

 above reaction. 



With strong HNO3 there is an evolution of brown fumes and a gas 

 which burns with a smoky flame. Glacial acetic acid slowly decomposes 

 it. By fusion with NaOH this carbide is decomposed and a gas is evolved 

 which is probably acetylene. At i8o°C calcium carbide is decomposed 

 by alcohol, thus : — 



2C2H,OH-fCaC2=C2H2+(C2H50;2Ca. 

 The simple reaction with water is : — 



CaC2+2H20=Ca(OH)2+C2H2. 



