1885.] 



The Chemical Constitution of Isatin. 



203 



difies soon after to a yellow crystalline mass, which is easily obtained 

 pure by pressing and recry stall i sing from, absolute alcohol to which 

 some acetone has been added. The new compound, the amide of the 

 above nitro-anthranilic acid, crystallises in yellow needles, is difficultly 

 soluble even in hot water and in boiling alcohol, but easily in acetone. 



It decomposes at a temperature between 200° and 210°. 0'236 gram 

 of the compound dried over H 2 S0 4 gave at 9° and 760 mm. bar., 

 45 c.c. N. N=22*93 per cent. 



9a 1 



Calculated for C 6 N0 >CONH : N=23*20 per cent. 



Reduction of Nitro-Isatoic Acid. 



On treating nitro-isatoic acid with tin and tolerably concentrated 

 hydrochloric acid, with gentle warming, much carbonic acid besides 

 hydrogen escaped, which led one to suppose that a reduction product 

 of the above nitro-amidobenzoic acid was formed, and this was verified 

 by the examination of the resulting solution. In this there was con- 

 tained the hydrochloric acid salt of a diamidobenzoic acid, which, from 

 its relation to the above nitroanthranilic acid, may be termed amido- 

 anthranilic acid. Its formation is shown by the following equation : — 



H 3 -] H 3 1 



C 6 N0 ^CO,COOH + H 6 =C 6 NHo > COOH + COo + H 2 0. 

 N J NHj 



The above solution was first freed from tin by means of sulphuretted 

 hydrogen, and then, in order to prevent decomposition setting in 

 during the subsequent evaporation, a few crystals of acid sulphite of 

 soda were added.* Notwithstanding this, the solution became brown- 

 coloured, and deposited, when sufficiently concentrated, a salt likewise 

 dark in colour, which after pressing was recrystallised from hot water 

 containing a little hydrochloric acid. The pale-yellow salt thus got, 

 crystallising in small prisms, has the composition of hydrochloric- 

 diamidobenzoic acid : C 6 H 3 (NH 2 ) 2 COOH.2HCl. 



0*235 gram of the salt, dried over sulphuric acid, gave on precipi- 

 tation with nitrate of silver 0*302 gram AgCl = 31'79 per cent. CI; 

 calculated^: 31*51 per cent. 



The sulphuric-diamidobenzoic acid, 



C 6 H 3 (NH 2 ) 2 COOH.S0 2 (OH) 2 , 



prepared from the above salt, crystallises from water in hard trans- 



* Compare Griess regarding liis investigation upon diamidobenzoic acid. " Liebip's 

 Ann. Chem. Pharm.," Bd. 154, 325. 



P 2 



