400 T. S. Hunt on Chemical Classifications. 



searching for some principle which shall enable ns to arrange this 

 large class of products, the first question to be settled is, to which 

 of the parent bodies does their type pertain? For example, is an 

 ether to be regarded as a species derived from the acid or the alco- 

 hol, by the mutual action of which it is formed ? A correct an- 

 swer to this question is necessary before we can arrive at a right 

 understanding of the laws of combination, and the principles 

 upon which these compound, are to be classified. 



The ingenious but partial views of the two great schools of 



the day, those of Liebig on the one hand, and those of Gerhard t 



and Laurent on the other, have failed to give a satisfactory an- 

 swer, or to remove the many difficulties that environ the subject. 

 There seems to be a portion of truth in both systems which each 

 is unwilling to concede to the other. The two systems may 

 be best compared by an examination of some well known com- 

 pounds. Oxalic acid (C 3 H 2 0,) which is bibasic, yields by its 

 action upon one equivalent of alcohol (C, H fi O), the oxalovinic 

 acid C 4 H 6 4 , which equals (O t H-, 4 4*G 2 H, 0)~H 2 0; 

 while with two equivalents of alcohol, oxalic ether C 6 H, 4 

 is formed, which is equal to(C 2 H 2 4 + 2C 2 H 6 0)-2H a O. 

 These two compounds are distinguished from several isomeric 

 bodies by the results of their decomposition ; in the presence of 

 alkalies they can resume the elements of water and regenerate 

 alcohol and an oxalate; — a reaction which shows that in these 

 bodies, there is a constitutional or functional relation to oxalic 

 acid and alcohol. 



It now becomes desirable to define the nature of that relation 

 so that it may be represented by formulas. Mr. Gerhard t, keeping 

 in view the electro-chemical ideas of Berzelins, supposes the acid to 

 act upon the alcohol or rather upon its hydrogen by virtue of its 

 oxygen, so that the various acids in relation to alcohols, ammonia 

 and hydrocarbons, may be regarded as electro-negative, while the 

 latter are electro-positive.* According to this hypothesis, in the 

 formation of oxalovinic acid, where H , O has been eliminated, 

 the acid has lost O while the alcohol haslost H 2 , so that the com- 

 pound is to be regarded as an alcohol in which oxalic acid minus 

 O replaces H, ; or rather making the electro-negative the generic 

 type, oxalic acid where alcohol minus H. replaces oxygen. In 

 the same manner, oxalic ether is the acid in which a second 

 equivalent of oxygen is replaced by the same elements. Repre- 

 senting C 2 H 6 0-H 2 by Et: 





Oxalovinic acid = C„ H f (O, Et) 

 Oxalic ether = C" 2 H , ( O a Et 3 ) 





* Precis, torn, ii, p. 495. 



