228 



Colouring Principles. 



626. ISATIN. C 16 H 10 N 2 4 . 



a. Deep red prismatic crystals. 



Note. Prepared by treating indigo with sulphuric acid and bichromate 

 of potassium. 



627. ANILIC ACID. C 7 H 5 N 8 . 



a. White crystalline powder. 

 Note. Formed by the action of boiling nitric acid on indigo. 



628. ANTHRANILIC ACID. C 7 H 7 N O 3 . (PhenyLCarlamic Acid, 



Carbanilic Acid.) 

 a. White powder. 



629. LITMUS. 



a. Deep blue angular fragments. 



Note. Obtained from Boccella fuciformis, R. tinctoria, and B. Mon- 

 tagnei. See Mat. Med. Catalogue, p. 160, No. 133. 



630. ALIZARIN. C U H 8 4 . 



a. Bright red acicular crystals. 

 Note. This specimen was prepared by sublimation. 



631. PURPURIN. C 14 H 8 5 . 



a. Dark red acicular crystals. 

 e.- -Obtained from madder by treatment with alum and sulphuric 



acid. 



632. G-ARANCIN. 



a. Purplish powder. 

 Note. Produced by the action of sulphuric acid upon madder. 



633. HffiMATOXYLIN. C 16 H 14 6 . 



a. Small lumps consisting of radiating prismatic crystals. 



Note. Obtained from logwood. See Mat. Med. Catalogue, p. 86, 

 No. 194. 



634. PURREE. (Indian Telloio.) 



a. Yellow amorphous pieces. 



Note. This substance is said to be made from camel's urine. It is 

 used in oil, and water-colour painting. It is stated to be a magnesia salt 

 of euxanthic acid. See P. J. [1] , vol. iv., p. 417. 



635. CHRYSAMMIC ACID. C 14 H 8 N 4 12 . 



a. Yellow powder. 

 Note. Obtained by the action of nitric acid on aloes. 



636. CHRTSAMMATE OF POTASSIUM. K C 7 H N 3 6 . 



a. Dark brown crystalline powder. 



Note. The crystals have a greenish metallic lustre, like that of 

 murexide. 





