256 HISTORY OF CHEMISTRY. [LECTURE XIII. 



as the foundation of an edifice, and in this connection, our 

 thanks are due to Kekule, who, in his excellent text-book, 

 has furnished us with the proofs. Although Kekule has been 

 reproached from many sides, that in carrying out the principles 

 he had advanced, he does not always adhere to them faithfully 

 an accusation which is not altogether groundless still I 

 wish to point out that any such want of adherence only took 

 place in cases where the facts were insufficient at the time for 

 a final decision, and that a quite consistent observance of the 

 principles was, therefore, scarcely possible. It may be pointed 

 out here, however, that at the very time when many difficulties 

 attended the employment of structural formulae, and when 

 ambiguities frequently arose, Butlerow 13 and Erlenmeyer 14 

 constantly advocated them with much zeal. 



It is not the business of a historical account to follow 

 in detail the establishment of general principles. Such an 

 account must be confined, rather, to developing the history of 

 the rise and decline of prominent ideas ; whereas the enume- 

 ration of the facts, and their arrangement from one common 

 view-point, constitute the sum and substance of the science 

 itself, and must, consequently, be dealt with in text-books. I 

 shall therefore content myself by adducing here what was 

 actually of service in strengthening the system, what led to 

 new conceptions or opinions, what appears to be irreconcilable 

 with the principles and leads us to expect an expansion or 

 alteration of the present theories. 



I shall begin with a description of the discussion regarding 

 the constitution of lactic acid, which took place within the 

 period 1858-60, and led to the distinction between atomicity 

 and basicity in the case of acids. Following the lead of 

 Gerhardt, who regarded lactic acid as a dibasic acid, 15 many 

 chemists doubled the formula for this acid and wrote it 

 C 12 H 12 O r) [C = 6, O = 8], whereas the interesting synthesis of 

 alanine, and the conversion of this compound into lactic acid 



13 Zeitschrift fiir Chemie. 4, 549 ; 6, 500. 14 Ibid. 7, i. 15 Gerhardt, 

 Traite. I, 689, 



