210 HISTORY OF CHEMISTRY. [LECTURE XI. 



might almost say, absolute confirmation. His experiments, 

 moreover, are not chosen at random, but are always sug- 

 gested by the same kind of logical deductions. Williamson 

 furnished thinking chemists with the means of determining 

 molecular weights by chemical methods. The very general 

 applicability of the method which he discovered, is demon- 

 strated by the fine experiments of Gerhardt, who was led by it 

 to the preparation of the mixed anhydrides, 41 and of Wurtz, 

 who employed it with similar success in fixing the formulae of 

 the alcohol radicals. 4 - The mode, also, in which Friedel and 

 Crafts 43 determined the molecular weight of silicic ether depends 

 upon a train of ideas that only became clear to chemists after 

 the publication of Williamson's investigations. 



The fact must not remain unmentioned here that, only a 

 few months after Williamson's publication, Chancel, on yth 

 October 1850, published a paper 44 in which, by means of 

 similar experiments, he arrived at the same results as William- 

 son. Chancel distils potassium ethyl sulphate with potassium 

 ethylate, and with potassium methylate, and thus obtains ethyl 

 ether and ethyl methyl ether. His mode of fixing the mole- 

 cular weight of dibasic- acids is peculiar to himself, although 

 it coincides, in principle, with Williamson's method. By dis- 

 tilling potassium ethyl sulphate with potassium methyl car- 

 bonate, and with potassium methyl oxalate, Chancel prepares 

 ethyl methyl carbonate and ethyl methyl oxalate. The reac- 

 tions are represented by the following equations : 



co ' (CH K + so < (cfnj K = co (cn 



The experiments of Williamson and of Chancel were of the 

 greatest importance in the development of the science, for our 

 present views are founded upon the conception of the chemical 

 molecule. Unfortunately it is not always possible to determine 



41 Ann. Chim. [3] 37, 332 ; Annalen. 82, 127 ; 83, 112 ; 87, 57 and 149. 

 42 Ibid. 96, 364. ^ Ann. Chim. [4] 9, 5. 44 Coniptes Rendus. 31, 521. 



