918 NEUTRAL COLOURING MATTERS. 



potash salt. M. Piria has also observed the formation of 

 picric acid in the treatment of hydruret of salicyl with nitric acid. 



Chlorisatin, C 32 H 4 NC1O 3 .* When chlorine gas is transmitted 

 through water in which blue indigo is suspended, hydrochloric 

 acid is formed, and the indigo is converted into a reddish yellow 

 matter, which Erdmann has found to be a mixture of several 

 new products, of which the most remarkable are two chlorine 

 compounds, which have been named chlorisatin andbichlorisatin. 

 When the yellow matter is digested in boiling water, a resin is 

 left undissolved, and a solution formed, which on cooling, de- 

 posits a reddish yellow crystalline powder, which is a mixture 

 of the two compounds mentioned. When this is dissolved in 

 boiling alcohol, the chlorisatin crystallizes out first. It forms 

 orange-yellow, four-sided prisms, is bitter, soluble in alcohol, 

 but highly insoluble in cold water. It is partially decomposed 

 by sublimation. 



Chlorisatin dissolves in a solution of caustic potash, of a red 

 colour. When heated, the colour of this solution changes to 

 yellow, and a potash salt crystallizes on cooling, in shining 

 plates, of which the composition is KO-f C 32 H 5 NC1O 4 . It 

 contains chlorisatinic acid, into which, under the influence of 

 bases, chlorisatin is converted, by the fixation of the elements 

 of an atom of water. Strong acids throw down chlorisatin 

 again from the potash salt. The salt of lead is a yellow preci- 

 pitate, which becomes of a fine scarlet on standing. The salt of 

 copper is thrown down brownish yellow, but becomes blood-red 

 and granular. 



Bichlorisatin, C 32 H 4 NC1 2 O 3 ; contains twice as much chlorine 

 as chlorisatin, but greatly resembles it in properties, and is 

 analogous in its relation to alkalies. The salt of lead of its 

 acid is permanently yellow ; the copper salt, which first appears 

 as a brown gelatinous precipitate, soon becomes greenish yellow, 

 and then of a splendid blood-red and granular. It is said 

 to form a very fine red on drying, and to take a gold lustre by 

 friction. 



Chlorisatyde, C 32 H 5 NC1O 3 ; a white substance, which is 

 formed when sulphuretted hydrogen is sent through a solution 



* So named from Tsatis tinctoria. These formulae are to be considered 

 with reference to the formula ascribed to blue indigo, by M. Erdmann, 

 namely C 33 H ]0 N 2 O 3 . 



