On Oxalic Acid. 103 



history of the properties of oxalic acid^ but merely to state 

 the result of a set of experiments, undertaken with the view 

 of ascertaining different particulars respecting it^ which I 

 conceived to be of importance. 



I. Water of Crystallization. 



Oxalic acid is usually obtained in transparent prismatic 

 crystals more or less regular; these crystals contain a portion 

 of water, for when moderately heated they effloresce and 

 lose a part of their weight, which they afterwards recovef 

 when left exposed in a moist place. When cautiously heated 

 on a sand bath they fall to powder, and lose about a third 

 of their weight. But as the acid is itself volatile, it is not 

 probable that the whole of this loss is water. To ascertaia 

 the quantity of water contained in ihese crystals 1 had re- 

 course to the following method : 



1. Seventy gr.-^ins of crystallized oxalic acid were dis- 

 solved in 600 grains of water, constituting a solution which 

 weighed 670 grains. \ 



Fifty grains of pure carbonate of lime, in the state of caF- 

 careous spar, were dissolved in muriatic acid ; this solution 

 was evaporated to dryness to get rid of the excess of acid, 

 and the residue redissolved in water. 



Into this muriate of lime the solution of oxalic acid was 

 dropt by little and little as long as any precipitate fell, and 

 the oxalate of lime thus formed was separated by the filter. 

 Pure oxalic acid is not capable of precipitating the whole 

 lime from solution of muriate of lime, the muriatic acid 

 evolved being always sufficient to retain the last portions in 

 solution. 



It was necessary to get rid of this excess of acid ; the 

 method which appeared the least exceptionable was to satu- 

 rate the niuriallc acid with ammonia : accordingly, when the 

 oxalic acid ceased to occasion any further precipitate, I 

 cautiously added pure ammonia, till the liquid ceased to 

 produce any effect upon vegetable blues. A copious addi- 

 tional precipitate of oxalate of lime was thus obtained. Ox- 

 alic acid was now added again as long as it rendered the 

 linuld niuddy. By thus alternately having recourse to the 



G 4 * acid 



