ETHYLENE, also known as olefiant gas or ethene, is found in coal gas and is the first representative, or H2C : of the series of olefine hydrocarbons. It is a colourless gas of some what sweetish taste, slightly soluble in water, but more so in alcohol and ether. It can be liquefied at - I • I ° C, under a pres sure of 421 atmos. It solidifies at -18I° C and melts at -169° C; it boils at -105° C (L. P. Cailletet), or to C (K. Olszewski). Its critical temperature is 13° C. It is usually prepared by heating a mixture of ethyl alcohol and sulphuric acid. G. S. Newth (1901) obtained a purer product by dropping ethyl alcohol into syrupy phosphoric acid (sp. gr. 1.75) warmed to 200° C, subsequently raising the temperature to 220° C. A variant of this process is employed in the manufacture of ethylene when alcohol vapour is passed at 300° C over charcoal impreg nated with phosphoric acid. It is also manufactured by passing alcohol vapour over heated alumina at 360° C. Scientific interest attaches to its preparation from (I) ethyl bromide and alcoholic potash; (2) the electrolysis of a concentrated solution of potas sium succinate.
Ethylene burns with a bright luminous flame (see FLAME), and forms a very explosive mixture with oxygen. On heating it decomposes, giving, among other products, carbon, methane and acetylene (M. Berthelot, 1866). Being an unsaturated hydro carbon, it is capable of forming addition products, e.g., it com bines with hydrogen in the presence of platinum black or heated nickel to form ethane, with chlorine and bromine to yield the cor responding ethylene dihalides, with sulphuric acid at 16o-170° C to form ethyl sulphuric acid, and with aqueous hypo chlorous acid to form glycol chlorhydrin, It com bines with sulphur trioxide and with halogen hydrides. Dilute potassium permanganate solution oxidizes it to ethylene glycol, whilst fuming nitric acid converts it into oxalic acid. Several compounds of ethylene and metallic chlorides are known ; with ferric chloride and platinous chloride in hydro chloric acid it gives and respectively. When inhaled ethylene is a general anaesthetic (Luckhardt and Carter, 1923). It is given with 7–I 2% of oxygen, but caution is necessary because this mixture of gases is explosive. To deepen the ethylene anaesthesia, ether may be added.