LECTURE XII.] HISTORY OF CHEMISTRY. 243 



His conception of the acids of phosphorus is likewise interesting. 

 Odling writes : 



Ordinary phosphoric acid ,-T J-O 3 

 Pyrophosphoric acid - |r fO 6 



Jrl 4-' 



PO'"1 

 Metaphosphoric acid HJ ^ L> 



PO'^PFF "'i 

 Phosphorous acid VT j-O 5 



T)TT '/' 



Hypophosphorous acid j| O. 2 . 



According to Odling, therefore, phosphorous acid stands to 

 pyrophosphoric acid in the same relation as hypophosphorous 

 acid to metaphosphoric acid. A similar relation exists between 

 dithionic and sulphuric acid on the one hand, and oxalic acid 

 and carbonic acid on the other : 

 CO 



Carbonic Oxalic Sulphuric Dithionic 



acid. acid. acid. acid. 



Kay, a pupil of Williamson's, 6 ' 2 almost simultaneously pub- 

 lished a research (obviously suggested by his teacher) which 

 deserves our notice. By the action of sodium ethylate upon 

 chloroform, he had obtained an ether which he called tribasic 

 formic ether, and which had been produced according to the 

 following equation : 



4. ? 2 5 O O 4- -7 MsP1 



C1 3 + 3 Na ( ~(C 2 H 5 ) 3 * + 3N 



Williamson specially draws attention to the fact that the resi- 

 dues of three molecules of alcohol are held together in the 

 new substance by the trivalent radical CH. This was the first 

 example of a polyatomic hydrocarbon radical, and it was soon 

 to be shown how valuable was this mode of regarding the sub- 

 stance. Berthelot, occupied at the time with the investigation 

 of glycerine (which was completed in 1854 so far as its most 



& Proc, Roy, Soc. 7, 135, 



