Anthranilic Acid — Indigo — Chlorisatinic Acid, Sfc. 35 



Anthranilic /Icid. 

 Liebig has given a short notice on the method of preparing 

 this acid, and on some of its properties; he found Fritzsche's 

 statement of its decomposition perfecdy correct. It is best 

 to mix the acid with twice its weight of coarsely powdered 

 glass. He found the composition the same as Fritzsche. — 

 Annalen der Chem. und Fharmacie^ vol. xxxix. 



Indigo. 



Dumas has published a paper on this interesting body, and 

 some of its compounds : when the indigo-blue is prepared by 

 means of sulphate of iron and lime, and precipitation by an 

 acid, it frequently contains sulphur, from which it may be freed 

 by treatment with sulphuret of carbon. Dumas gives the 

 formula as C^^ H'*' N'^ O'^; he does not agree with Erdmann. 

 Very cai-efully prepared reduced indigo gave, on analysis, the 

 formula C^^' H^'^ N^ O^. Dumas therefore compares it to oil 

 of bitter almonds. 



Indigo-sidphuric Acid. — If we wish intirely to prevent the 

 formation of the purple acid, we must use not eight but fifteen 

 parts of concentrated sulphuric acid to one of pure indigo- 

 blue, and allow the whole to digest in a bottle for several days 

 at a temperature between 50° and 60° C. The formula of 

 the potash salt is C^^ H« O, 2 S O^ + K O. The baryta salt 

 has a precisely similar formula. 



Purpuro-sulphuric Acid. — This is formed when eight or ten 

 parts of sulphuric acid are used; it is put on a filter and washed 

 with dilute hydrochloric acid. Its formula is C^^ H^° N"* 0% 

 2SO^. 



Indigotic Acid.— lis formula was found to beC^" H^^N^ O'^'; 

 the silver salt, C'" H^ W 01° + Ag O, &c. 



Picriimitric ^c/rf.— Formula C>^ H'' W O^''; the silver salt 

 is C*2 !!•* W O'^ + Ag O : the potash salt contains one atom 

 of water. — Ann, deChim. et de F/i^s., trois. ser. ii. p. 204. 



Marchand has published researches on the above acid and 

 its salts; he finds for the free acid the formula C^'^ H^ N^ O''*, 

 both when prepared from indigo and from salicin. He finds 

 the potash salt to be anhydrous. The baryta, strontia and 

 lime salts contain five atoms of water of crystallization ; there 

 are basic salts of baryta and strontia which contain two atoms 

 of base. The magnesia salt seems also to contain five atoms 

 of water. [An abstract of the conclusion of this paper in our 

 next.] 



Chlorisatifiic Acid, Chlorisatyd, 8j-c. 

 Erdmann has published a third treatise on Indigo, in which 

 he corrects some of his previous formulae. Laurent had com- 



D2 



