41 6 COMPOUND PRODUCTS. CHAP. I. 



denominated artificial acids. They are consequently 

 not within the scope of the object of the present 

 work. 



SUBSECTION I. 



Oxalic Acid. If the expressed juice of the Oxalis 

 ucetosella is left to evaporate slowly, it deposits 

 small crystals of a yellowish colour and saltish taste, 

 which are known by the name of the acidulum of 

 Sorrel, that is, a salt with excess of acid, from which 

 the acid may be obtained pure by processes well 

 known to the chemist. 



Oxalic acid, in its state of purity, is always con- 

 crete. Its taste is sharp and acrid. It is readily 

 soluble in cold water, and is distinguished from other 

 acids by its property of decomposing all calcareous 

 salts, and forming with lime a salt 'insoluble in 

 water. Hence it is used by chemists as a test to 

 detect the presence of calcareous salts. But it is 

 not used in medicine or the arts except in its state 

 of acidulum, in which it is employed to make a sort 

 of lemonade, and to discharge stains of ink. It has 

 been found also in O.ralis corruculata, Geranium 

 acidum, in the several species of Rumex, and in the 

 pubescence of Cicer arietinum. 



SUBSECTION II. 



Acetic Acid. The Acetic Acid or vinegar^ 

 which is generally manufactured from wine in a 



