CHEMICAL SCIENCE. 22T 



them in the same relation as ether does to alcohol. The researches of 

 M. Cahours had led to the discovery of a series of bodies necessary 

 for Gerhardt's process. These were obtained by the action of penta- 

 chloride of phosphorus on various organic acids, and consisted of chlo- 

 rine combined with the oxygenized radical of the acid. Thus from 

 benzoic acid was prepared the chloride of benzoil, C 7 H 5 O Cl, and 

 the corresponding bodies, from cuminic, cinnamic, and various other 

 acids. Gerhardt has since made, by the same process the body C 2 H 3 

 O Cl, which is the chloride of the radical of acetic acid, called othyl. 

 Now, on bringing any one of these chlorides in contact with the potas- 

 sium salt of the corresponding acid, the chemical force of combination 

 between chlorine and potassium induced the decomposition. These 

 results can be most simply stated in the form adopted by M. Gerhardt, 

 the discoverer, which consists in comparing the composition of these 

 bodies with that of water, from which they are formed, by the substi- 

 tution of one or both atoms of hydrogen by organic radicals. Thus 



water being represented by the formula T O, acetic acid is formed 

 from it by the action of chloride of othyl C 2 H 3 O Cl, which forms 



C 2 H 3 ^ O * H Cl i. e. hvdrated acetic acid and hydrochloric acid. 



H 

 If a second atom of chloride of othvl is made to act upon this acetic 



TT O 



acid, or better, upon the acetate of potash, C 2 jr 3 O, we get, be- 



f 1 TT O 



sides chloride of potassium, a compound /v J Q 0, which, when 



compared to the original type, may be considered as water having 

 both its atoms of hydrogen replaced by the radical othyl, C 2 H 3 O. 

 This compound is the anhydrous acetic acid which might be called the 

 acetate acid of othyl, inasmuch as that radical has, in the formation of 

 the compound, taken the place of the basic potassium in the acetate of 



C 1 TT O 



potash. In like manner, the anhydrous benzoic acid n 7 u 5 , ) O was 



* v/j X5 \J 



made by the action of the chloride of benzoil C 3 H 5 O Cl on the ben- 

 zoate of potash. It is a crystalline body, perfectly neutral to test pa l 

 per, scarcely soluble in water, readily soluble in alcohol and ether. 

 On continued boiling with water, it is converted into hydrated benzoic 

 acid, one atom of the anhydride with one atom of water forming two 

 atoms of the hydrated acid by an interchange of hydrogen and ben- 

 zoil. Besides several of these anhydrous acids, Gerhardt has prepared 

 some intermediate acids, analogous to the intermediate ethers, by com- 

 binino- two different radicals in the same group. Thus chloride of 



C H O 



benzoil with cuminate of potash 10 T ^ u O formed cuminate of 



benzoil or benzocuminic acid n 10 -rr 11 r O ; and in like manner seve- 



U 7 1 5 U 



ral other intermediate acids were prepared. In conclusion, to this 

 very brief exposition of this important series of discoveries, the lec- 

 turer alluded to a feature of the development of the human mind in. 



