LECTURE XII.] HISTORY OF CHEMISTRY. 245 



extent impaired by taking account of pyrophosphoric and meta- 

 phosphoric acids. Odling's orthophosphoric acid 64 has neither 

 the same composition nor the same basicity as these two latter 

 acids, whilst it is always the same substance, glycerine, which is 

 contained in the ethers prepared by Berthelot. Wurtz was 

 happier in his view of these remarkable facts, looking, as he 

 did, upon glycerine as a triatomic alcohol and representing it as 



c* TT "'1 



S 5 "O G . 05 T ne compounds examined by Berthelot are 



W 3 J 



produced, according to Wurtz, by the replacement of one, two, 

 and three hydrogen atoms by acid radicals. In this connec- 

 tion he points out how the monatomic group C H r passes into 

 the trivalent residue QH 5 by loss of H 2 . [C = 6, O = 8.] 



It could not escape the notice of a clever investigator like 

 Wurtz that the existence of monatomic and of triatomic alcohols 

 necessarily involves that of diatomic alcohols, and he at once 

 institutes experiments which have for their aim the preparation 

 of such substances. From his way of looking at the subject 

 he necessarily expected a diatomic radical in the still hypo- 

 thetical alcohol ; the univalent group C 6 H r and the trivalent 

 group C, 3 H 5 rendered possible the formation of the monatomic 

 and of the triatomic alcohols ; the homologues of C^H,. must 

 correspond to the diatomic alcohols. 66 The chlorides and 

 bromides which were already well known (in part, at least) 

 favoured the accuracy of this view, and it was now simply a 

 question of converting them into the corresponding hydroxy- 

 compounds and the object was attained. The action of the 

 basic hydroxides did not realise the hopes which Wurtz had 

 entertained, but earlier experiences now came to his aid. 

 Four years previously, he had discovered a reaction whereby a 

 similar conversion could be carried out ; 6T and this reaction 

 had subsequently proved serviceable in several cases. 68 It was 

 now to appear that it deserved to be called a general method. 



64 Phil. Mag. [4] 18, 368. 65 Ann. Chim. [3] 43, 492. 66 Compare 

 Odling, Journ. Roy. Inst. 2, 62. 67 Comptes Rendus. 35, 310; 39, 335 ; 

 Ann. Chim. [3] 42, 129. 68 Zinin, Annalen. 96, 361 ; Cahours and 

 Hofmann, ibid. IOO, 356. 



