36 Notices of the Labours of Cojitinental Chemists. 



menced reseaixhes upon indigo, mention of which is made in 

 the ComptesRendus, torn. xii. p. 539, wherein he corrects some of 

 Erdmann's formulae. Erdmann found the correct formula for 

 chlorisatin to be C**'' H^ N^ CI'- O^' Chlorisatinic acid must 

 therefore also be different. Chlorisatyd is Ci« W" W CP O^. 

 By the action of hydrosulphuric acid on chlorisatin a white 

 insoluble body is formed, sulpho-chlorisatin ; its formula is 

 Q\6 iiio ^2 Q\i gs Erdmann formerly stated that bichlorisatin 

 contained the same number of atoms of hydrogen as chlori- 

 satin : it appears, however, from his later experiments, which he 

 made on account of Laurent's statements, that this is not the 

 case; the formula is, according to Laurent, C^*" H'' N^ CH O"*. 

 [This is the reason why in this abstract I have not called these 

 bodies chloride and bichloride of isatin. — H. C.]. The for- 

 mula of bichlorisatyd is C'^ H^ N^ CI* O*. 



By the action of dilute chromic acid on indigo-blue, a very 

 curious body, isatin, has been discovered both by Laurent and 

 Erdmann ; it crystallizes in large dark red crystals. Isatin is 

 but little soluble in cold water, but more so in hot, with which it 

 forms dark reddish yellow solution. When heated a small 

 part sublimes, but the greater portion is decomposed. Formula 

 Qi6 pjio ]s^2 Q4^ jIjjjj jg^ indigo plus two atoms of hydrogen. 

 When treated with chlorine it is converted into a mixture of 

 chlorisatin and bichlorisatin : it dissolves in caustic potassa 

 with a dark purple colour. Hydrochloric acid precipitates 

 from the solution a reddish yellow crystalline powder, which 

 appears to be unchanged isatin ; if however the solution be 

 heated or allowed to stand for some time, it becomes bright 

 yellow, and gives on evaporation a crystallized potash salt 

 soluble in alcohol : this salt contains isatinic acid. Isatin takes 

 up an atom of water to form this acid. The silver salt is partly 

 soluble; the solution of the salt cannot be heated without de- 

 composition. Formula C^^' H^^ W 0\ Ag O. When a solution 

 of isatinate of potassa is treated in the cold with hydrochloric 

 acid no change ensues, but when warmed pure isatin is preci- 

 pitated. 



Isatin dissolves completely in hydrosulphuret of ammonium 

 when heat is applied : on cooling, a white or yellowish some- 

 what crystalline powder is precipitated, which does not con- 

 tain any sulphur: this Erdmann calls isatyd. Formula 

 C""' H'- W CF. Isatin reacts therefore quite differently from 

 chlorisatin. Isatyd is scarcely soluble in water, gives a cry- 

 stalline salt when dissolved in potash by the aid of heat. 



By the action of hydrosulphuric acid on an alcoholic solu- 

 tion of isatin, a new body, sulphisatin, is formed ; its formula is 

 not yet fully determined.— Erdmann, Journal fiir Praia. ChevUf 

 vol. xxiv. p. 1 ; Laurent, Comptes Itendus, vol. xii. p. 539. 



