Anthocyanins and Anthocyanidins. 



159 



hydrochloric acid, using excess of magnesium, and wlien the reduction was 

 completed, adding magnesium acetate. 



In order to show that the pigments obtained by the above-mentioned 

 authors were not pure products, experiments were then made as follows. 

 Chemically pure crystalline samples of cyanin chloride, violanin chloride, and 

 quercitrin were used. 



(i) Magnesium acetate was added to a fresh alcoholic solution of (a) cyanin 

 chloride ; {h) violanin chloride. In each case a fine pure blue pigment was 

 formed, which did not change when precipitated and washed with ether. 



(ii) Magnesium acetate was added to a solution of quercitrin in alcohol ; a 

 bright yellow colour developed and yellow-green fluorescence. Ether precipi- 

 tated a yellow pigment (Mg salt), which did not change when washed with 

 ether. 



(iii) Magnesium acetate was added to solutions containing {a) a mixture of 

 cyanin chloride and quercitrin, and (h) a mixture of violanin chloride and 

 quercitrin. In each case green pigments were at once produced, and the 

 solutions showed the same bright green fluorescence as when the reduction 

 above described was carried out. Precipitation and washing with ether left 

 the green pigments (mixtures) unchanged. 



(iv) An alcoholic solution of magnesium acetate was made, filtered, and 

 ether added ; — magnesium acetate was precipitated. 



These results prove that the analyses of the green pigments described by 

 the above mentioned authors are valueless. 



By adjustment of the proportions of cyanin chloride and quercitrin in 

 Experiment iii {a), the green pigment obtained by reduction of quercitrin was 

 readily matched. 



Further observations respecting the reaction of anthocyan pigments with 

 metallic salts, which have been made from time to time, appear to be of 

 sufficient interest to insert here. In particular, those on violanin, as this 

 would most nearly correspond to the reduction products obtained from 

 myricetin or myricitrin. 



(i) To separate portions of a fresh solution of violanin chloride in alcohol 

 {circa 95 per cent.) there were added : (a) magnesium acetate, (&) calcium 

 acetate, (c) anhydrous sodium acetate ; in each case a fine pure blue was at 

 once produced, and on standing, the whole of the colour was gradually 

 deposited as an indigo-blue flocculent precipitate. The colour of the blue 

 solutions could not be distinguished from one another. The blue precipitates 

 were all soluble in water, but were insoluble in absolute or 95 per cent, 

 alcohol. The dilute solutions of these precipitates become decolorised on 

 standing, owing to pseudo-base formation, 



