2l4 HISTORY OF CHEMISTRY. [LECTURE XI. 



Williamson shows how the existence of dibasic acids depends 

 upon the presence of radicals with basicity greater than one. 55 

 The formation of the substituted ammonias, in the reaction 

 discovered by Wurtz, which he formulates : 



2 r _i_ Qi"i /rr\ 2 n _i_ ^2**| rr 



(H 2 ) 2 + N ( CO ' = (CO) 2 + N H ' J 



gives him occasion to express himself as follows : " One atom 

 of carbonic oxide is here equivalent to 2 atoms of hydrogen, 

 and by replacing them, holds together the 2 atoms of hydrate 

 in which they were contained, thus necessarily forming a 



bibasic compound, ^ -^ ' CX, carbonate of potash." 



JS.O 



By further assuming that carbonic oxide can double its 

 atomic weight, without alteration of its basicity (or equivalence), 

 he obtains in C 2 O 2 the radical of oxalic acid, and is able to 

 represent the formation of oxamide by means of the equation : 



(C 2 H 5 ) 2 Q N H H _ /C 2 H 5 o \ (CO) 2 

 (C0) 2 U ' 2 + ? 2 2 4 ~ V H U / + N 2 H 4 ' 



The conception of sulphuric acid as a dibasic hydrate of 

 the radical SO 2 is highly important, and the experiments which 

 Williamson carries out in support of this view, are most inter- 

 esting. Besides the known chloride SO 2 C1 2 , which Regnault 

 had prepared from sulphurous anhydride and chlorine, 50 he 

 succeeds in isolating also chlorosulphonic acid, by treating 

 sulphuric acid with phosphorus pentachloride. 57 

 Thus : 



H r] 



O 



u <=;n 



S0 2 + PC1 5 - b Y? + POC1 3 + HC1. 

 O g 



H 



By means of this experiment he disproves the view of Ger- 

 hardt, in accordance with which the formation of the anhydride 

 is always supposed to precede that of the chloride in the case 



55 Journ. Chem. Soc. 4, 350. 56 Ann. Chim. [2] 69, 170; 71, 445. 



57 Proc. Roy. Soc. 7, 1 1 ; Annalen. 92, 242. 



