208 Notices of the Labours of Continental Chemists. 



chlorindoptenic acid. This body has a disagreeable smell, 

 behaves similar to chloriiulopten, reacts acid, gives with a salt 

 of silver a voluminous yellow precipitate, with lead a white 

 one. Formula of silver salt is C'-H-Cl^. Ag; formula of 

 free acid C- H^ Cl^ O. 



After the chloride of indopten has been distilled off, the 

 residue is boiled with a large quantity of water, a resinous 

 matter remains behind, and the filtered solution deposits a 

 a red body ; on evaporation more is obtained, but less pure. 

 This substance is dissolved in boiling alcohol ; on cooling, 

 reddish-yellow or brown crystals are deposited ; these are 

 chloride of isatin, with a little bichloride of isatin and resin: 

 by repeated crystallizations it may be obtained pure. It is 

 inodorous, bitter, may be heated to 160° C. without decompo- 

 sition, above that temperature it is partly decomposed and 

 partly sublimed; 100 parts of alcohol of 0*83 dissolve 0"453 

 parts of it. It is neutral, not altered by hydrochloric or 

 sulphuric acids; is decomposed by nitric acid. Formula 

 C"^H*NC10'. Treated with caustic potassa it is dissolved 

 with a yellow colour; it takes up an atom of water and forms 

 chlorisatinic acid. The potash salt crystallizes easily, is pu- 

 rified by solution in alcohol, &c,; the acid cannot be separated 

 when precipitated by an acid out of the potash salt; it decom- 

 poses and forms chloride of isatin, which body may in this man- 

 ner be obtained perfectly pure. Potash salt explodes. For- 

 mula C'« H-^ NCI O^K. Silver salt is C-^H^ N CI 0\kg. 

 There are two salts with baryta, one with one atom of wa- 

 ter, the other with three. The lead salt is at first yellow 

 and gelatinous, but becomes flocculent and of a splendid 

 red colour. The copper salt is at first yellowish-brown, 

 but becomes granular and blood-red, &c., &c., &c. Bi- 

 chloride of isatin remains in the alcoholic solution out of 

 which the chloride has been obtained ; out of this it may be 

 obtained : of course the latter crystallizations are the freest 

 from the protochloride. These two bodies are extremely 

 similar; the bichloride differs from the other in being more 

 soluble in alcohol, and the bichlorisatinate of potash gives 

 with lead salts a yellow precipitate, which does not become 

 red like the chlorisatinate. Bichloride of isatin is, when ob- 

 tained from its aqueous solution, a yellowish-red granular 

 powder; out of alcohol it crystallizes in red shining needles 

 and tables; sometimes four-sided prisms may be recognised; 

 it may be partly sublimed, but the greater part is decom- 

 posed ; more soluble in water than the protochloride. 100 

 parts alcohol of O'SS dissolve at 14-° 3*40 parts. Formula 



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