INDIGO-WHITE. 385 



and this mass then heated with zinc-dust and soda- 

 lime. 



Properties. Deep blue, approaching purple ; pressure 

 gives it a copper color and a half metallic lustre. 

 Tasteless, inodorous; completely insoluble in water, 

 alcohol, ether, dilute sulphuric acid, hydrochloric 

 acid, and alkalies ; soluble in anilin. At about 300, 

 it is transformed into a purple vapor, which condenses 

 in the form of lustrous, deep copper-colored prisms ; 

 this property can also be made use of for the purpose 

 of preparing pure indigo, though it involves loss in 

 consequence of decomposition and carbonization. Dis- 

 tilled with potassium hydroxide, it is resolved into 

 anilin and carbonic acid. When boiled for a long 

 time with potassa-ley and finely-divided black oxide of 

 manganese, it is converted into anthranilic acid (p. 

 330). 



Indigo -white, C 16 H 12 N 2 2 . Is produced from in- 

 digo-blue when this comes in contact with nascent 

 hydrogen or with any other reducing agents in the 

 presence of a base. It is contained in the solutions 

 described above, which are not colored blue, and can 

 be obtained from them in an isolated condition when 

 they are allowed to flow directly into boiled, dilute 

 hydrochloric acid by means of a siphon, care being 

 taken that they do not come in contact with air. The 

 indigo-white is thus separated in the form of white, 

 glittering flocks. 



After being filtered off and washed with water, that 

 has been boiled for a long time, it must be dried 

 either in a vacuum or in a current of hydrogen. 

 White, fine, crystalline powder ; inodorous and taste- 

 less ; insoluble in water. In contact with air, particu- 

 larly when in a moist condition or in water containing 

 air, it is soon reconverted into indigo-blue. It is a 

 weak acid, and is readily dissolved by alkalies, forming 

 yellow solutions. These solutions, as well as its salts 

 formed by double decomposition, are exceedingly un- 

 33 



