104 AROMATIC COMPOUNDS AND [CH. 



pour into a little strong hydrochloric acid. Then add ether to the mixture in a 

 separating funnel. A crude precipitate of peonin chloride will separate out after a 

 time, which may be more or less crystalline. Filter off this precipitate, take up in 

 water and make the following experiments : 



(a) Take two equal quantities of the solution in two evaporating dishes. To one 

 add solid sodium chloride as in Expt. 106 (6). Then neutralize both portions carefully 

 with very dilute sodium carbonate solution until the colour changes slightly to 

 purple. The colour will fade more rapidly in the solution without sodium chloride 

 on account of the formation of a colourless isomer, as in the case of pelargonin 

 chloride. The water solution after standing will give a green colour with alkali owing 

 to admixture with the yellow salt of the isomer. 



(6) Add alkali. A deep blue colour is produced. A crude extract of the fresh 

 petals made as in Expt. 101 will give a green or bluish-green colour with alkali owing 

 to the presence of the accompanying flavone. 



(c) Add amyl alcohol and sulphuric acid. No colour is taken up by alcohol. The 

 pigment is present as the glucoside peonin. Boil another portion with sulphuric 

 acid and add amyl alcohol. The pigment is partly hydrolyzed and the peonidin goes 

 into solution in the alcohol. 



(d] Eeduce another portion with zinc dust and hydrochloric acid. The colour 

 returns after filtering. 



In considering the anthocyan pigments, the question now arises 

 What is the chemical significance of the various shades in the living 

 plant ? Apparently the same pigment may be present in two flowers 

 of totally different colours, as in the blue Cornflower and the magenta 

 Rosa gallica. It has been suggested that in such cases the pigment is 

 modified by other substances present in the cell-sap: thus it may be 

 present in one flower as a potassium salt, in another as an oxonium salt 

 of an organic acid, and in a third in the unaltered condition. But exactly 

 how these conditions are brought about is not clear. In one or two 

 cases, moreover, where there is a red or pink variety of a blue or purple 

 flower, the variety, when examined, has been found to contain a different 

 pigment and one less highly oxidized than that in the species itself. 

 The above phenomena are exemplified in the Cornflower (Centaur ea 

 Cyanus). The flowers of the blue type contain the potassium salt of 

 cyanin, the purple variety, cyanin itself, while those of the pink variety 

 contain pelargonin. 



The mode of origin of anthocyan pigments in the plant is as yet 

 obscure. It has been suggested (Wheldale, 29) that they have an 

 intimate connexion with the flavone and flavonol pigments, which can 

 be seen at once by comparing the structural formula of quercetin with 

 that suggested for cyanidin : 



