418 RUBIANIC ACID. 



ftuercitin, C 27 H 18 12 , which also occurs ready formed 

 in Calluna vulgaris, in tea, in the root-bark and trunk- 

 bark of the apple-tree and other plants. Yellow, crys- 

 talline powder, sublimes in large yellow needles with 

 partial decomposition. But slightly soluble in water, 

 easily soluble in alcohol. Fusing potassa decomposes 

 it, like phloretin, into phloroglucin and quercetic acid, 

 C 15 H 10 7 , which crystallizes in fine, silky prisms; 

 sparingly soluble in cold water. By further treatment 

 with fusing potassa, it yields protocatechuic acid (p. 356), 

 quercimeric acid, C 8 H 6 5 -f H 2 and paradatiscetin, 

 C 15 H 10 6 . 



Rutin is a glucoside, very similar to quercitrin, but 

 not identical with it, contained in Ruta graveolens 

 the loppers (blossom-buds) of Capparis spinosa. Yields, 

 when treated with acids, quercitin and an unferment- 

 able sugar, which appears to be different from isodul- 

 cite. 



7. Frangulin. 



Q20JJ20Q10. 



In the bark of Rhamnus frangula. Yellow, crys- 

 talline mass ; fusing point, 226. Almost insoluble in 

 cold water, difficultly soluble in cold alcohol and ether, 

 easily in hot alcohol. Soluble in alkalies, forming red 

 solutions. Acids resolve it into sugar and frangulic 

 acid, C 14 H 10 5 + H 2 0, which forms an orange-yellow, 

 loose crystalline mass, but slightly soluble in water, 

 easily soluble in alcohol ; fusing point, 246-248. 



8. Rubianic Acid. 



C 20 H 22 11 (?), 



In madder (the root of Rubia tinctorum). In order 

 to prepare it, fresh madder-root is boiled with water, 

 foreign substances removed from the solution by means 

 of ^ neutral lead acetate, the liquid filtered, the rubianic 

 acid precipitated from it by means of basic lead acetate, 



