LECTURE XI.] HISTORY OF CHEMISTRY. 213 



Gerhardt had at once grasped the bearings of Williamson's 

 investigations, and was only able to perceive in them confirma- 

 tion of the views already upheld, at an earlier date, by himself 

 and Laurent, but never stated with the same precision. 53 He 

 perceived that Williamson's reaction for the formation of ether 

 might also be applied to the monobasic acids, and that the 

 oxides or anhydrides of the latter should be obtained in this 

 way. 54 The experiment succeeded, and thus it was reserved 

 for Gerhardt, who, as well as Laurent, had denied the existence 

 of anhydrides of monobasic acids, to disprove this view by his 

 own experiments. He had, it is true, previously only stated 

 the impossibility of withdrawing a molecule of water from one 

 molecule of acid, and this statement still held ; for he showed 

 that two molecules of a monobasic acid are always concerned 

 in the formation of the anhydride, and the proof was furnished 

 by Williamson's method. By treatment of potassium acetate 

 with acetyl chloride, Gerhardt obtained acetic anhydride : 



CaH ' ] O + C 2 H 3 OC1 - g^g j O + KC1, 



and by employing benzoyl chloride he obtained the intermediate 

 anhydride of benzoic and of acetic acids : 



Before turning to the researches carried out jointly by 

 Gerhardt and Chiozza on the anhydrides and amides of dibasic 

 acids, I must give an account of the conception which William- 

 son introduced concerning these acids, whereby the stimulus 

 was given that led to these researches. The extension which 

 Williamson gave in 1851 (that is, a year after his first investi- 

 gation on etherification) to the views already arrived at, was an 

 extremely important one. Even if it may perhaps be said that 

 in his previous publications he leaned towards the views of 

 Laurent and Gerhardt, and merely confirmed these by means 

 of new, although certainly most decisive experiments, he now 

 appears in a perfectly independent and original manner. 



53 See his claim : Annalen. 91, 198. 54 Ann. Chim. [3] 37, 332. 



