the Rheum Palmatum, or Rhubarb. 291 



lime had existed in the root, before its destruction by fire, 100 

 grains of rhubarb were deprived of all soluble matter by the 

 action of alcohol and water ; these solutions were evaporated, 

 and the residue submitted to a red heat in an open platinum cru- 

 cible burned away, leaving no appretiable portion of earthy alca- 

 line or saline matter, a small trace of common salt and of lime 

 excepted. The insoluble woody fibre was digested in muriatic 

 acid, and the solution saturated by ammonia : it gave a preci- 

 pitate weighing 8.5 grains, from which, by the action of sul- 

 phuric acid, a portion of malic acid was separated. If this pre- 

 cipitate, therefore, be regarded as composed of phosphate and 

 malate of lime, it would consist of 



Phosphate of lime 2. (12) 



Malate of lime • • 6.5 



8.5 



15. The component parts of rhubarb, therefore, would ap- 

 pear from the whole of the preceding data, to be as follow : — 



Water 8.2 (10) 



Gum 31.0 (5) 



Resin 10.0 (7) 



Extract tan and gallic acid .... 26.0 (8) 



Phosphate of lime 2. (12) 



Malate of lime 6,5 (14) 



Woody fibre 16.3 (5) 



100.0 



16. The very copious precipitate obtained by adding solution 

 of acetate of lead to infusion of rhubarb, induced me to hope 

 that some peculiar principle might be found in it, combined with 

 the metallic oxide ; I therefore collected a quantity of the com- 

 pound, difiused it in water, and passed sulphuretted hydrogen 

 through the mixture, which was afterwards boiled, filtered, and 

 evaporated to dryness : a brown viscid substance, of a peculiar 

 smell, and somewhat acid flavour, remained, which I was at 



