474 CONSIDERATION OF CARBON COMPOUNDS. 



methyl ; CH 2 H , methylene ; CH m , meihenyl ; and of carbon C Uii . The 

 univalent radicals such as methyl, ethyl, propyl are called alkyl or 

 alcohol radicals, while the term alkylene designates bivalent radicals 

 such as methylene, ethylene, propylene, etc. 



A characteristic feature of these halogen derivatives is the behavior of the 

 halogens towards such reagents as silver nitrate. Chlorine and iodine when in 

 combination with hydrogen or metals readily form with a soluble silver salt 

 insoluble chloride or iodide. The halogens which have replaced hydrogen in 

 organic compounds are, as a general rule, not affected by silver salts in solu- 

 tion. This behavior shows that the substitution products are not dissociable 

 i. e., there are no halogen ions present. While above a general method has 

 been given by which the halogen compounds can be made, there are usually 

 employed other processes for their manufacture. Also the names given above 

 are not always those in general use. Thus, trichlor-methane or methenyl 

 chloride is generally called chloroform and the corresponding bromine and 

 iodine compounds bromoform and iodoform. 



Methyl chloride, CH 3 C1 (Monochlor-methane), is readily obtainable by the 

 action of hydrochloric acid on methyl alcohol : 



CH 3 OH + HC1 = CH 3 C1 + H 2 O. 



It is a colorless, inflammable gas which can be liquefied by pressure. This 

 liquid which produces an intense cold by its evaporation has been used locally 

 for neuralgia. 



Dichlor-methane, CH 2 C1 2 (Methylene chloride), is obtained by the action of 

 nascent hydrogen on chloroform : 



CHC1 3 + 2H = CH 8 Cl a + HC1. 



It is a colorless, oily liquid, boiling at 40 C. (104 F.) ; sp. gr. 1.344. It has 

 an odor similar to that of chloroform, and has been employed as an anaesthetic. 



Tetrachlor-methane, CC1 4 (Carbon tefrachloride), is obtained by the action 

 of chlorine on carbon disulphide, or by treating chloroform with iodine chloride : 



CH.CL, -f IC1 = CC1 4 + HI. 



It is a colorless liquid possessing anaesthetic properties, but, like the previous 

 compound, is dangerous. 



By far the most important halogen derivatives of methane are the 

 trisubstitution products : chloroform, bromoform and iodoform. The 

 gaseous chlorine and the liquid bromine convert through their sub- 

 stitution the gaseous methane into colorless, heavy, volatile liquids, 

 while the solid iodine confers the solid state upon the compound. 



Chloroform, Chloroformum, CHOI, = 118.45 (Trichlor-methane), 

 is obtained by the action of bleaching-powder and calcium hydroxide 



