152 FOLYGONACEM 



a fluid extract with, basic acetate of lead- In eaeli ease separate 

 the base by means of sulphuric acid, and the organic acid by 

 means of ether. Allow the ethereal solution to evaporate, and 

 treat the residue with distilled water, and filter ; this separates 

 the resin (resinous acid). The filtrate is then filtered through 

 animal charcoal repeatedly, until all colouring matter isremoYcd. 

 The filtrate is next treated with solution of gelatine, in order to 

 remove any tannic acid that might be present, again filtered, 

 and evaporated to dryness, redissolved in ether, and the ethereal 

 solution allowed to evaporate spontaneously* Polygenic acid 

 thus prepared crystallizes in needles. Its solution in water does 

 not precipitate gelatine nor produce a bluish-green coloration 

 when added to a mixture of ferrous and ferric salts in solution, 

 showing absence both of gallic and tannic acids. It is freely 

 soluble in water, less so in ether, and insoluble in petroleum 

 spirit. The heat of a water-bath does not destroy any of its 

 properties. ( Year-Book of Pharm,, 1886, p. 210. ) 



The other species of Polygonum which have been examined 

 contain starch and tannic and gallic acids. Bowman (1869) 

 obtained 21 per cent, of tannic acid from Bistort root. In the 

 Bengal Chemical Examiner's Heport for 1884 we meet with the 

 following notice of P. glahrum : '^ Several specimens of a pl^^* 

 caUed Bish-kurki were sent from Cachar for examination. 1* 

 was stated that the plant was frequently added to country 

 spirit, which it was believed might have thus communicated to 

 it some specially noxious property. The plant was identified 

 by Dr. Gr. King as Pohjgomtm glabnim^ and on chemical exami- 

 nation and physiological application was not found to possess 

 toxic properties/' 



RHEUM OFFICINALE, Baiiion. 



Flg.^Bentl and Trim., t. 213. Rhubarb (Eng.), B^^^' 

 barbe (Fn). 



Hab. —South-Eastern Tibet, China. The root. 



