ON THE STATE OF ORGANIC CHEMISTRY. 3 



a terchloride differs from a protochloride. Thus a protohydrate, alcohol, 



C 2 H 5 1 



„ O, for example, is converted into a chloride by the action of one 



atom of hydrochloric acid, one atom of water being at the same time elimi- 

 nated, — 



C H }o + HCl-H 2 = C 2 H 5 Cl, 



Alcohol. Chloride of ethyl. 



and cannot then be any further acted on in the same way. 



Glycerine is similarly converted into a chloride, with elimination of an 

 atom of water, by the action of one atom of hydrochloric acid, 



° 3 H 3 } ° 3 + H Cl-H 2 0=C 3 H 7 2 CI ; 



Glycerine. Monochlorhydrin. 



but the product in this case can again produce the same reaction with a 

 second, and even with a third atom of hydrochloric acid : — 



C 3 H 7 O 2 Cl+H Cl-H 2 0=C 3 H 6 O CI 2 



Monochlorhydrin. Dichlorhydrin. 



C 3 H 6 O CI + H Cl-H 2 0=C 3 H 5 CI 3 



Dichlorhydrin . Trichlorhy drin. 



And iu general terms, we may express the difference between a polyatomic 

 body and a monatomic body, deriving from the same type, by saying that, 

 with the same reagent, both produce similar reactions, but that a greater 

 quantity of the reagent (two, three, or four times as much, according as the 

 substance is di-, tri-, or tetratamic) is required to react to the greatest pos- 

 sible extent with the polyatomic body than with the monatomic body. 



The consideration of the following and similar series of bodies — 



CH 4 Marsh-gas, 



C H 3 CI Chloride of methyl, 



C H 2 CI 2 Chloride of methylene, 



C H CI 3 Chloroform, 



C CI 4 Bichloride of carbon, 



throws great light upon the mutual relations of monatomic and polyatomic 

 substances. The second term of the series is a monatomic chloride ; it re- 

 acts with one atom, but not with more, of potash, ammonia, &c. The third 

 is a diatomic* chloride, the fourth a triatomic f chloride, and the fifth a te- 

 tratomic 4 ; chloride. The radicles which these four chlorides respectively 

 contain are (CH 3 )', (CH 2 )", (CH)'", and (C) iv , all formed from marsh-gas 

 (C H 4 ), the first term of the series, by the removal of hydrogen ; and the 

 number of atoms of hydrogen which must be removed to form each radicle 

 denotes the atomic value of that radicle. In other words, chloride of methyl, 

 CH 3 CI, can, under a variety of conditions, part with its chlorine in exchange 

 for other substances, whilst its carbon and hydrogen remain in unaltered 

 combination, having the characters of a monatomic radicle. But, under cer- 

 tain other conditions, chloride of methyl can exchange one-third, two-thirds, 

 or even the whole of its hydrogen against an equivalent quantity of chlorine ; 

 and the compounds which are formed, containing C H 2 CI 2 , C HCl 3 , and C CI 4 , 



* No reactions corresponding to this view of chloride of methylene are yet known, hut 

 the analogy of iodide of methylene (Comp. Buttlerow, Ann. Chim. Phys. [3 J liii. 313) is 

 sufficient for our present purpose. 



t Comp. Kay, Chein. Soc. Quart. Journ. vii. 224 ; Hofmann, Proc. Roy. Soc. ix. 229. 



j Comp. Hofmann, Proc. Roy. Soc. ix. 284. 



b2 



