CHEMISTRY 217 



But if a hydroxyl group be substituted, as in 

 glycolic acid, CH 2 OHCOOH, or a chlorine 

 atom, as in monochloracetic acid, CH 2 C1* 

 COOH, the acidity is greatly increased, while 

 the compound trichloracetic acid, CC1 3 - 

 COOH, is a strong acid. On the other hand, 

 aminoacetic acid, CH 2 *NH 2 -COOH, is 

 scarcely acid at all. 



The effect of introducing a carboxyl group 

 in place of a methyl group into any paraffine 

 hydrocarbon, regardless of its constitution, 

 e.g. CHa-CHg-^CHs-COOH, is to diminish 

 the heat of combustion of the molecule almost 

 exactly 157 calories ; but the conversion of 

 acetic acid into oxalic acid, CH 3 *COOH-> 

 COOH -COOH, structurally an identical 

 change, diminishes the molecular heat of 

 combustion only 147 calories. 1 In both these 

 instances it is certain that the nature of the 

 influence of the radicals consisting of carbon 

 and hydrogen exclusively is nearly independ- 

 ent of their size and configuration. Any 

 other group, however, by its presence at once 

 modifies the nature of the case, though un- 

 concerned in the process or property. Since 

 it can be shown that such effects, like the 

 difference between monochloracetic acid and 



1 Stohmann, Zeitschrift fur Physikalische Chemie. II, 29, 

 1888. 



