178 Lapper and Bell — On the Distillation of Saccharates. 



With regard to the cause of the difference in the behaviour of the 

 two acids, but little can be said. According to all experiments 

 hitherto published, it is extremely probable, if not absolutely certain, 

 that the relative position of the carbon atoms is the same in both. 

 Both are normal compounds ; and the differences between them must 

 be due to the positions of their hydroxyl groups. If we give to either 

 acid {e. g. mucic acid) the formula 



CO3H _ CH(OH) - CH(OH) - CH(OH) - CH(OH) - COoH, 



and to pyrrol the constitution proposed by Baeyer, 



H 

 HC = C. 



I >H, 

 HC = C"^ 



H 



the formation of the latter is easily explained — 



COOH 



I H 



II(OH)C - CH(OH) HC = C 



II +NH3= I >NH 



H(OH)C - CH(OH) C= C 



I H H 



COOH 



+ 2C0o + 4H2O. 



At the same time one or both of the carboxyl groups may become 

 amidated, and may remain with the pyrrol nucleus. In saccharic 

 acid now we may imagine a greater number of hydroxyl groups to be 

 joined to the carbon atoms in the neighbourhood of the carboxyl, and 

 consequently the latter to be rendered unstable. Hence, when 

 ammonium saccharate is distilled, it parts with both carboxyl groups, 

 and gives pyrrol, but no carbopyrrolic acid. This explanation is 

 reasonable, for we know that oxy acids as a rule lose CO2 much more 

 easily than the acids from which they are derived, and those in whicli 

 the OH is near the carboxyl more easily than those in which it is 

 remote from it. Thus, succinic acid, when heated, yields an anhy- 

 dride, whilst tartaric acid (dioxysuccinic acid) decomposes into car- 

 bonic anhydride and pyroracemic acid. Again, salicylic acid separates 

 more easily into phenol and COo than either of its isomerides, para- 

 and meta-oxybenzoic acids; whilst benzoic acid may be distilled 

 unchanged. Many similar examples might be adduced. 



We purpose studying the action of ammonia on other highly oxy- 

 genated acids. 



