Intelligence and Miscellaneous Articles. 567 



ON HIPPURIC ACID, BENZOIC ACID, AND THE SUGAR OF 

 GELATINE. 



M. Dessaignes remarks, that hippuric acid has already been the 

 subject of numerous researches ; its metamorphoses are nevertheless 

 so interesting as to leave something for those to glean who will study 

 it. M. Liebig has shown, that when it is dissolved in boiling hydro- 

 chloric acid, it crystallizes on cooling without having been altered ; 

 but if the ebullition be prolonged for about half an hour, it is decom- 

 posed, and yields, according to M. Dessaignes, benzoic acid equal 

 nearly in quantity to that indicated by theory. The benzoic acid was 

 separated by the filter, and the filtered liquor gave by evaporation long, 

 acid, nitrogenous prismatic crystals, into the composition of which 

 hydrochloric acid entered as a constituent part. These crystals were 

 neutralized by carbonate of soda or carbonate of lead ; and after 

 getting rid of the solution of chloride of sodium or chloride of lead, 

 fresh crystals of a very saccharine and azotized matter were ob- 

 tained ; these were neutral to reagents, and formed crystalline com- 

 pounds with oxide of silver, and with nitric, sulphuric, and oxalic 

 acids. 



M. Dessaignes soon found out that he had thus produced, by a 

 metamorphosis which might have been foreseen, the sugar of gela- 

 tine discovered by M. Braconnot. 



Reckoning C=150, H=6-25, and N=17*5, if from 



C ,s H 18 N 2 6 

 we subtract C 14 H 12 O 4 



we obtain C 4 H 6 N 2 O 2 



to which it is sufficient to add 1| equivalent of water to obtain sugar 

 of gelatine. M. Dessaignes is inclined to the opinion, that 2 equiva- 

 lents of water should be added, and that the true equivalent of sugar 

 of gelatine is O H 10 N 2 O 4 , as already indicated by M. Gerhardt. 



All the reactions and beautiful crystallizations which M. Des- 

 saignes obtained with the saccharine azotized matter from hippuric 

 acid, convinced him of the identity of this substance with the sugar 

 of gelatine obtained from isinglass ; but in order to convince chemists 

 of this fact, he thinks it requisite to analyse the sugar of hippuric 

 acid. The metamoi'phosis which gives rise to this body is very di- 

 stinct ; no gas is evolved during the reaction ; the only two products 

 are benzoic acid and hydrochlorate of sugar. From ] 00 of dry hip- 

 puric acid M. Dessaignes obtained, — 



Benzoic acid (dry) 67*49 



Hydrochlorate of sugar (dried over sulphuric acid) 59*08 



126*57 



Nitric acid boiled for twenty minutes with hippuric acid, converts 

 it into benzoic acid, and nitro-saccharic acid, which crystallizes in 

 magnificent truncated tables. Nitro-saccharic acid, prepared with 

 the sugar of isinglass, yielded precisely similar crystals. 



