Hydrocarbons of the Acetylene Series Diolefines

The graphic formula of acetylene which is used to represent the structure of its molecule and to indicate that it is capable of adding to itself four univalent atoms is HC = CH. In such 

The hydrocarbons in this series are usually named as substitution-products of acetylene for example, methyl-acetylene, dimethyl-acetylene, etc. In another system of nomenclature the name of any hydrocarbon is derived from that of the saturated hydrocarbon which contains the same number of carbon atoms, by replacing the termination ane by ine thus, acetylene, C2H2, is called ethine, and methyl-acetylene, CHsC CH, propine. Some of the hydrocarbons have, in addition, names which were given them when they were first prepared. Propine is often called, for example, allylene. 

Acetylene, C2H2.—This hydrocarbon is the most important in the series on account of the fact that it illustrates in its reactions the chemical conduct of its homologues, and because it has been applied to a number of important uses. 

Acetylene is a gas which has a garlic-like odor. Under a pressure of 48 atmospheres at 1° it condenses to a colorless liquid which has the specific gravity 0.45 and boils at 82.4 . Acetylene is slightly soluble in most liquids one volume of water, benzene, and alcohol dissolve one, four, and six volumes, respectively, of the hydrocarbon. One volume of acetone dissolves at the ordinary temperature and pressure 25 volumes, and at a pressure of 12 atmospheres 300 volumes of acetylene. 

The carbon monoxide and hydrogen formed burn on the extreme edge of the flame. If a metal is to be cut, an excess of oxygen is used and the supply of acetylene is shut off after the proper temperature has been reached. The hot metal burns in the stream of oxygen, and as the torch is slowly moved a narrow cut is made. 

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