62 THE ISOLATION AND [CH. 



a brown powder, very soluble in water, and having the properties of 

 a tannin. Gautier, in fact, considers all three acids to be coloured 

 tannins. 



Glan (176), 1892. The flower- pigment of Althaea rosea. 



The petals, after treatment with petrol ether, were extracted with 

 alcohol ; the alcohol was distilled oft', and the residue taken up in water 

 and precipitated with lead acetate. The lead salt was then decomposed 

 with sulphuretted hydrogen, and after concentration, the residue was 

 extracted with alcohol and the solution poured into ether, from which 

 the pigment separated out in red flakes. In properties it is a dark red 

 powder, insoluble in ether, chloroform, etc., and soluble in water and 

 alcohol. It gives a green colour with ammonia and alkaline carbonates, 

 a blue pigment with normal, and a green precipitate with basic lead 

 acetate. When the pigment is heated with dilute sulphuric acid, 

 sugar is split off, and the sugar-free product is insoluble in water. 



The composition of the pigment before heating with sulphuric acid is : 



C H 



48-43% 6-18% 45-39% 



and after heating with acid: 



C H 



54-46 % 5-81 % 39-37 % 



When the solution of the pigment in sulphuric acid is neutralised 

 with potash, a neutral potassium compound of the pigment separates 

 out in blue flakes. The potassium salt has the following composition: 



C H O K 



48-32% 5-62% 39-73% 6-32% 



Heise (178), 1894. The pigment from fruits of the Bilberry. 



The pigment was first precipitated with lead acetate, and the lead 

 salt was then decomposed with hydrochloric acid ether. After drying, 

 the residue was taken up with methyl alcohol and precipitated with 

 ether. This product was found to consist of two substances, one of 

 which occurs in excess, and is separated from the other by its solubility 

 in acidified water. There are two methods of separating the two 

 pigments (termed A and B). (1) The mixture is warmed with water 

 acidified with hydrochloric acid; B goes into solution, A does not. 

 The pigment B can be purified again by precipitating with lead acetate, 

 decomposing with hydrochloric acid ether, taking up with methyl 



