OXALIC ACID IN R«UBARB. gg^ 



Indeed it is well known, that ihe acidulous oxalate of pot- 

 ash is scarcely soluble in tbs arienstruuin. 



The residuum that was insoluble in alcohol contained 

 acidulous oxalate of potash. Being- calcined and incine- 

 i-ated in a platina cviicible, a vcn- alkaline, white, melted f<^t^sh found 

 mass was obtained. Its concentrated solution changed the 

 acid sulphate of alumina into alum. This substanpe there- 

 fore was nothing but nearlj'^ pure potash, a little carbonated, 

 and containing a very small quantity of sulphate and mu- 

 riate of potash. 



From this examination of the juice of the stalks and Results, 

 leaves of the rheum palmalum, or true rhubarb, it follows, 

 that it contains, I, a pretty large quantity of acidulous 

 oxalate of potash : 2, an uncrystallizable acid combined 

 with the colouring extractive matter, which is analogous to 

 the acetic arid, and in this state exhil)its some of the pro- 

 perties ascribed to the ; » Id termed malic: 3, and lastly, 

 that the presence of this acid confirms in some measure the 

 experiments of the celebrated Scheele. We need uot be at 

 all surprised to tlnd oxalate of lime in the root of rhubarb, 

 since an acidulous oxalate of potash is obtained from its 

 leaves. 



Rhubarb is not the only root, that contains oxalate of Various roots 

 lime, for Scheele found it in several others; but as this salt [°'^'^J"j°^^* 

 exists in them in very small quantity, he employed a parti- 

 cular process to separate it, which we shall insert here, to 

 save trouble to those who would institute similar inquiries. 



Cut and bruise the roots, and pour on them muriatic M«thod of 

 acid diluted with a great deal of water. Leave them to di- <letectiug it, 

 gest a few hours ; then filter the solution, and saturate it 

 with ammonia. If the roots contain any oxalate of lirne, 

 this salt will be dissolved by the acid, and precipitated by 

 the alkali. 



The following subitances afforded this chemist more or Rf,ot> iirwliich^ 

 less oxalate of lime. 1, the roots of alkanet, parsley, car- '^ •'"* ^*='^'^ 

 line thistle, turmeric, white dittany, fennel, led gentian, 

 swallowwort, patience dock or rhubarb, liquorice, man- 

 drake, restharrow, Florentine orris, soapwort, squill, tor- 

 tnentil, valerian, zedoary, and ginger; and 2, the barks of and barks, 

 cafcarilla, cinnamon, elder, and siinarouba. 



XV. 



