260 HISTORY OF CHEMISTRY. [LECTURE XIII. 



regards lactic acid as dibasic, and as different in constitution 

 from glycollic acid. He is forced to this by the existence of 

 the lactates described by Briining and others. 



The first part of Kekule's text-book appeared in the same 

 year, and it was possible to see from it how easily the nature 

 of the lactic acids might be explained by reverting, as Kekule 

 did, to the elements themselves. For although he too 

 employs the mode of representation according to types, still 

 this is elucidated by means of the so-called graphic formulae 

 which are intended to express the relationships of the atoms. 

 These formulae constituted a new mode by which to represent 

 the constitution of compounds. They remained in use for 

 some time, but they were again replaced, at a later date, 

 by written formulae which approach to those introduced by 

 Couper. 



The following are examples of these formulae : 



CH 3 CH 3 CH,OH COOH 



i I I I 



CH 2 OH COOH CH 2 OH COOH 



Alcohol. Acetic acid. Glycol. Oxalic acid. 



The relations of the atoms in glycollic acid were furnished 

 to Kekule by the method for its formation from chloracetic 

 acid, which was discovered by himself. These relations can be 



CH 2 OH 

 represented by the formula . Both glycollic acid and 



COOH 



lactic acid contain two typical hydrogen atoms ; that is, as 

 Kekule now explains, 3 "* two atoms of hydrogen united to the 

 carbon by means of the oxygen. These two atoms differ in 

 their properties, inasmuch as the one behaves like the typical 

 hydrogen of acetic acid, being influenced by two oxygen atoms, 

 whilst the other plays a part resembling that of the typical 

 hydrogen in alcohol. The solution of the difficulty was now 

 supplied, since this view explained to the adherents of the 

 doctrine of atomicity, all the chemical reactions of glycollic acid, 



35 Kekule, Lehrbuch der Chemie. I, 130 and 174. 



