RHUBARB. 



Turkey rhubarb is generally preferred to the Eaft India 

 fort, though the latter is more aftringent, but has fome- 

 thing lefs of an aromatic flavour. Tin&ures made from 

 both, with equal quantities of rectified fpirit, have nearly 

 the fatm- talle ; on drawing off the menftrua, the extract 

 left by the tin&ure of the Eaft India rhubarb proves in 

 tafte considerably Stronger than the other. They feem 

 both, fays Dr. Lewis, to be the produce of the fame cli- 

 mate, and roots of the fame fpecies of plant, taken up pro- 

 bably at different feafons, or cured in a different manner. 

 Lewis's Mat. Med. 



The Ruffian rhubarb and Turkey rhubarb, fometimes 

 diftinguifhed in the fhops, feem to be the root of the fame 

 fpecies of plant, grown in the fame place, and prepared in 

 the fame manner ; but Mr. A. T. Thomfon (Loud. Difp.) 

 inclines to believe, that the Eaft Indian is the root of a dif- 

 ferent fpecies, very probably of the " undulatum ;" and the 

 mode of preparation appears to be evidently different, from 

 the afpect of the pieces. 



Good Ruffian or Turkey rlubarb, fays Mr. Thomfon, 

 has a peculiar, fomewhat aromatic odour, and a bitter, 

 flightly aftringent, fubacrid tafte ; feels gritty between the 

 teeth when chewed, and tinges the faliva of a bright yellow 

 colour. It breaks with a rough hackly fracture, is eafily pul- 

 verized, and affords a powder of a bright buff yellow colour. 

 Water at 2 12° takes up 24 parts in 60 ; the infufion is of a 

 brown colour, nearly clear, and reddens litmus paper. Al- 

 cohol extracts 2.7 from 10 parts, and gives a tincture of a 

 rich golden colour, which reddens tinfture of litmus ; is not 

 altered in its tranfparency by the addition of water ; and 



ftrikes a blackifh olive hue with folution of fulphate of iron, 

 but no immediate precipitate falls. Sulphuric ether takei 

 up 1.5 in 10 parts of this rhubarb; the tintture is of a 

 golden yellow hue, and when evaporated on water, leavee 

 a thin pellicle of yellow refin, and abundance of extractive 

 diflblved in the water, combined, however, with tannin. 

 Eaft Indian or Chinefe rhubarb has a rtronger odour, and 

 is more naufeous to the tafte than the Turkey ; breaks with 

 a more compact and fmoother frafture ; and affords a pow- 

 der of a redder fhade. Water takes up 30 parts in 60 ; the 

 infufion is not fo deep coloured as that of Ruffian rhubarb, 

 more turbid, and reddens alfo litmus paper. Alcohol ex- 

 tracts 4 parts in 10 ; the tinfture is of a much deeper co- 

 lour, and brownifh ; gives a deeper red to litmus tincture ; 

 is rendered flightly turbid by the addition of water ; and 

 ftrikes a green, not black, olive with fulphate of iron, which 

 it alfo quickly and copioufly precipitates. Ether takes up 

 2 parts in 10; the tincture is deeper coloured, and when 

 evaporated on water, affords the fame refults as the former 

 kind, except that the compound of tannin and extractive is 

 more foluble. 



The infufion of Chinefe rhubarb is more copioufly pre- 

 cipitated by folution of ilinglafs than that of the R.uffian. 

 Infufion of yellow cinchona throws down a copious greenifh 

 precipitate from infufion of Ruffian rhubarb, and a lefs 

 copious, but more denfe, bright yellow precipitate from 

 that of Chinefe rhubarb. 



The following tables fhew the effects of re-agents on tht 

 aqueous infufion of the two varieties of rhubarb. 



Table I. — Precipitates formed by Acids, Alkalies, and Neutral Salts. 



Table II. — Precipitates formed by Solutions of Metallic Salts. 



A a 2 



When 



