v] CONSTITUTION OF ANTHOCYANINS 61 



Heise is, apparently, not able to suggest any formulae for the pig- 

 ments on the basis of analysis. 



Gautier (175), 1892. The pigment from red Vine leaves. 



The extract of the pigment from the Vine leaves was precipitated 

 with neutral lead acetate until the colour of the precipitate becomes 

 blue. This first precipitate was then separated off, and precipitation 

 continued with the formation of a dark-green precipitate. The latter 

 precipitate was then decomposed with sulphuretted hydrogen, treated 

 with ether and taken up in 95 % alcohol. A red product was obtained 

 consisting of two substances and having, it is said, the characteristic 

 properties of a tannin. These substances are termed by Gautier 

 ampelochroic acids ; one was found to be insoluble in cold water 

 (a-ampelochroic acid) : the other soluble (/3-ampelochroiic acid). 



a-ampelochroic acid. After washing away the -/3-pigment with cold 

 water, the insoluble residue was taken up in hot water from which, on 

 cooling, the pigment separated out as a red crystalline powder. On 

 analysis the results were : 



C H 



56-43 % 3-96 % 39-61 % 



from which the formula C 19 H 16 10 is derived. 



According to Gautier, the a-acid is dibasic, and the normal lead 

 salt is dark green. The pigment is soluble in hot water and cold alcohol, 

 but is insoluble in ether. With ferric salts it gives a green-black 

 coloration. 



jS-ampelochroi'c acid. This is the portion soluble in cold water; 

 on slow evaporation, red crystals are deposited. The product is soluble 

 in water; the solution precipitates gelatine, and gives a violet-black 

 coloration with ferric salts. On analysis the results were: 



C HO 



(i) 53-89% 4-34% 41-77% 

 (li) 53-96 % 4-29 % 



with which the two following formulae agree most closely: 



c i7Hi 6 10 or C 26 H 24 15 



After determination of the molecular weight by means of the neutral 

 zinc salt, Gautier decides in favour of the formula C 26 H 24 15 . 



From the first precipitate originally obtained with lead acetate, 

 Gautier extracted by similar methods a third pigment y-ampelo- 

 chroic acid ; to this he gave the formula C 17 H 18 10 . It is described as 



