28 HYDROCARBONS. 



1. Marsh Gas (Fire Damp, Methyl Hydride), CH 4 . 



Occurrence and Formation. Together with the homo- 

 logous hydrocarbons, and mixed with carbonic acid 

 and nitrogen, it issues in many localities from the 

 earth ; frequently collects in mines and coal-beds. Is 

 formed in the process of putrefaction under water and 

 in the destructive distillation of a great many organic 

 bodies, and is hence contained in ordinary coal gas. It 

 is further formed when a mixture of the vapor of car- 

 bon bisulphide with sulphydric acid is conducted over 

 ignited metals ; from ethylene at a red heat ; and is 

 most readily obtained in a pure state by heating 2 parts 

 of crystallized sodium acetate with 2 parts of potassium 

 hydroxide and 3 parts of lime. 



Properties. Inodorous, inflammable gas, insoluble 

 in water, of specific gravity 0.559. Mixed with oxygen 

 or air it explodes with great violence when ignited ; 

 also when mixed with chlorine it forms a gas, which 

 explodes violently when exposed to direct sunlight. 

 In dispersed sunlight chlorine acts upon it in another 

 manner, displacing its hydrogen and forming the com- 

 pounds, CH 3 C1, CH 2 C1 2 , CHOI 3 and CC1 4 (treated of in 

 connection with methyl alcohol). 



2. Ethyl Hydride, C 2 H 6 . 



Is contained in a state of -solution in crude petroleum. 

 Is produced from the first substitution-products of 

 marsh gas (methyl chloride CH 3 C1, methyl iodide 

 CH 3 I) by the action of sodium or zinc ; by the decom- 

 position of a concentrated solution of sodium acetate 

 by means of an electrical current ; by the action of 

 water on zinc ethyl, or by heating ethyl iodide with 

 water and zinc in sealed tubes to 180. Colorless, 

 almost inodorous gas. Burns with a slightly lumi- 

 nous flame. Is but slightly absorbed by water, more 

 by alcohol. Chlorine displaces its hydrogen, forming 

 successively the compounds C 2 H 5 C1, C 2 H 4 C1 2 , C 2 IPC1 3 , 

 C 2 H 2 C1 4 , C 2 IIC1 5 , and C 2 C1 6 (see Ethyl Chloride). 



