196 Professor Kolbe. [Mar. 12, 



while at the same time a small amount of a substance crystallising 

 in needles sublimes. The yellow colour is characteristic of isatoic acid. 

 It is difficultly soluble in alcohol and glacial acetic acid, pretty diffi- 

 cultly in chloroform and benzol, and very slightly in ether. 



The acid (crystallised from acetone) dried over sulphuric acid m 

 vacuo, and then at 50°, yielded the following figures on analysis : — 



I. 0-4516 gram gave 0*9695 gram C0 2 , and 0-1307 gram H 2 = 

 58'5 per cent. C, and 3'2 per cent. H. 



II. 0-3349 gram gave 0*723 gram C0 2 , and 0'1307 gram H 2 = 

 58'9 per cent. C, and 3*3 per cent. H. 



0-3336 gram yielded 26'0 c.c. N (=0'03003 gram N) at 16° and 

 753 mm. pressure =8'4 per cent. ET. 



III. 0-284 gram gave 0-612 gram C0 2 , and 0'085 gram H 2 = 

 58' 75 per cent. C, and 3'35 per cent. H. 



The composition thus found agrees with that of a nitrogen-ben zoyl 

 carboxylic acid, (C 6 H 4 N,CO)COOH. 



Found. 



Calculated. I. II. III. 



C 8 96 58-9 58-5 58 '9 58 76 



H 5 5 3-0 3*2 3-3 3 3 



N 14 8-6 — 8-4 — 



O, 48 29-5 



163 100-0 



Adopting my idea of the composition of isatin, the process of its 

 oxidation by chromic acid when the above conditions are observed 

 proceeds, therefore, in this way, that the formyl of the isatin is 

 changed to carboxyl, whereby nitrogen-benzoyl carboxylic acid is 

 formed. (See Equation, p. 194.) 



The chemical behaviour of isatoic acid, so far as I have studied it, is 

 in complete harmony with the supposition that it is nitrogen-benzoyl 

 carboxylic acid. Of special importance for the right interpretation of 

 its chemical constitution are its close relations to anthranilic acid, i.e. y 

 o-amidobenzoic acid. It is readily and completely changed into the 

 latter (or its derivatives) by various reagents, carbonic acid being 

 separated and the elements of one molecule of water assimilated. 

 This transformation of isatoic acid into anthranilic acid is shown by 

 the following equation : — 



(0 6 H 4 N,0O)COOH+H 3 O = (C 6 H 4 NH a )COOH + CO 8 . 



The two atoms of hydrogen of the water combine with the atom of 

 nitrogen, which thereby becomes trivalent to amide ; the oxygen atom 

 of the water serves for the oxidation of the carbonyl, carbonic acid 



