288 Analj/sis of the Root of 



words not inserted in the dictionary, though he agrees with his 

 correspondent respecting the carelessness shown in the omis- 

 sion of numerous words, in classes of which other individuals 

 have been admitted* This is especially the case among minerals 

 and metals.] 



Art. VIII. An Analysis of the Root of the Rheum Pal- 

 matum, or Rhubarb, Bi/ W. T. Brande, S.R.S., Sec. 



1. There appears to have been no chemical investigation into 

 the nature of rhubarb, if we except a few experiments upon it 

 given in Neumann's Chemistry, where it is stated that a great 

 portion of it is soluble in water, and that alcohol scarcely 

 acts upon the residue. Neumann got from 480 grains 180 of al- 

 coholic, and afterwards 170 of watery extract; and inversely 

 350 watery, and only 5 of alcoholic extract. 



2. In the following experiments the finest Russian Rhubarb 

 was used, free from decay, and distinctly streaked with white and 

 red veins upon its cut surface : the former are chiefly gum, the 

 latter contain the extractive and astringent principle, as may 

 be shown by washing the surface with a dilute solution of 

 iron, when the red streaks only are discoloured. 



3. 100 grains of rhubarb, digested in eight ounces of boiling 

 water, till cold, gave a yellow-brown infusion, which was tested 

 by the following re-agents, and gave the annexed results : — 



Acetate of lead ........ a copious yellow precipitate, 



Sub-acetate of lead a red precipitate, 



Proto-muriate of tin .... a copious yellow precipitate, 



Proto-sulphate of iron , , , . an olive-green precipitate, 



Nitric acid , a brown precipitate, 



Oxalic acid , no effect. 



Infusion of galls no effect. 



Solution of gelatine a copious brown precipitate. 



4. It may be remarked, in respect to the above precipitates, 

 that nearly the whole of the colouring matter was carried doAvn 



