64 THE ISOLATION AND [CH. 



present in these solutions. Hence the pigment was extracted from the 

 dried petals with absolute alcohol ; the greater part of the alcohol 

 was then distilled off. an equal volume of water added, and the solution 

 precipitated with basic lead acetate. The green lead salt was suspended 

 in water, acidified w r ith hydrochloric acid, decomposed with sulphuretted 

 hydrogen, and filtered from lead sulphide. The deep red nitrate was 

 neutralised and left to evaporate : a dark red metallic powder remained 

 which was taken up in acetone and poured into a large quantity of ether, 

 whereupon the pigment separated out in granular plates. The product 

 was then treated with absolute alcohol, in which only a part was soluble, 

 the remainder being soluble in water. 



To the alcohol solution enough ether was then added to precipitate 

 the pigment as a brown precipitate, which was filtered off and taken 

 up again in absolute alcohol. After evaporation, the alcohol-soluble 

 pigment was deposited in tiny crystalline plates of a deep red colour. 



The water solution was evaporated in vacua and the residue taken up 

 again in a little acidified water, from which it was deposited as a granular 

 amorphous mass (the water-soluble pigment) which would not crystallise, 

 but gave concordant combustion results. 



The results of analysis of the two pigments were as follows : 



C H O 



The portion soluble in alcohol 60-10 % 5-62 % 34-28 % 



Calculated for C 14 H 16 6 ... 60-00 % 5-72 % 34-28 % 



The portion soluble in water 50-11 % 6-48 % 43-41 % 



Calculated for C 20 H 30 13 ... 50-21 % 6-27 % 43-52 % 



Determinations of the molecular weights were made by the lowering 

 of the freezing point of phenol. The results were : 



Molecular weight of the pigment soluble in alcohol ... 274 



Calculated for C 14 H 16 6 280 



Molecular weight of the pigment soluble in water ... 460 



Calculated for C 20 H 30 13 ... ... ... ... ... 478 



Grafe considers that the two pigments are related in the following 

 way: 



^20^30^13 + H 2 = C 14 H 18 8 + C 6 H 12 6 

 2C 14 H 18 8 2H 2 2 =-- 2C 14 H 16 6 



since the portion soluble in water reduced Fehling's solution, whereas 

 the portion soluble in alcohol did not; also dextrose could be split off 

 from the larger molecule by heating the substance in acid solution. 



