T. S. Hunt on Chemical Classifications. 91 



by the action of alkalies (as nitronaphthalene), but more frequently 

 the decomposition is less simple. By the prolonged action of 

 nitric acid aided by heat or the presence of concentrated sulphuric 

 acid, the compound first formed reacts with another equivalent of 

 the acid, eliminating a second time an equivalent of water; the 

 nitric species indeed comports itself with the acid, in all respects 

 like the normal one, and the product is still neutral. In like man- 

 ner some monobasic acids, as the benzoic, yield with nitric acid, 

 two or three acids, containing respectively one, two and three 

 equivalents of the nitric elements. These are strictly monobasic, 

 notwithstanding the apparent contravention of the law S = -2'- 1, 

 and it we consider their constitution in accordance with the prin- 

 ciple before laid down, we shall find that the second nitric body 

 is to be regarded as a coupled compound of the first, and so on. 

 Thus nitrobenzid being nitric acid where C 6 H 5 - O replaces H 

 or benzenic nitrate, binitrobenzid is nitrobenzenic nitrate, where 

 G 6 H 5 NO., -HO — C 6 H 4 NO replaces the hydrogen of a sec- 

 ond equivalent of nitric acid ; this being derived from a monoba- 

 sic acid and a neutral body, is necessarily neutral. The same 

 principle is applicable to the nitrobenzoic acids, as it is each time 

 a monobasic acid which is coupled with the nitric acid ; nitro- 

 phenisic acid contains the elements of three equivalents of nitric 

 acid, and yet possesses but one equivalent of replaceable hydrogen, 

 because the saline hydrogen of all these has been eliminated, and 

 only the original saline atom of the phenol remains. Represent- 

 ing this acid as phenol, in which NHO, replaces H 2 , thus; 

 ^ 6 (NH 0,)0,* it is difficult to see why it should not be tribasic. 

 The coupled acids which the sulphuric forms with many or- 

 ganic acids, are striking illustrations of Gerhardt's law: with one 

 equivalent of a monobasic acid, the compound is bibasic, but with 

 a bibasic acid as the succinic, it is tribasic ; the elements of the 

 succinic acid retaining in combination their saline capacity, while 

 the sulphuric has lost one equivalent of its hydrogen. The ethers 

 and ether-acids of these coupled bodies as the sulphacevinates of 

 Melsens, show how far these principles may be extended in the 

 study of organic compounds. 



; It now remains to consider the nature of that class of chlorin- 

 [zed compounds in which chlorine may be regarded as replacing 

 parogen, equivalent for equivalent. The close analogies sub- 

 sisting between the ethers of oxygen acids and the sulphuric and 

 Mtric copulates of the hydrocarbons being kept in view, we see 

 ln c » H 4 CI, (acetene chlore, Gerhardt.) the ether of hydrochlo- 

 pc acid, which is at the same time a chlorinized species of ace- 

 te "e, C 2 H 6 . 



The relation between phenol and benzene, is precisely similar 

 that which exists between alcohol and acetene, and the hydro- 



Precis, tom. lier., p. 97. 



