14 



Scheele. 



ON OXALIC ACID. 



^ny other substance, that I do not lose two pounds of the 

 colour in a ton of tlie ore. 



I remain, dear Sir, 



Your very humble servant, 



RIBBLESDALE. 



IV. 



On Oxalic Acid. Bij Thomas Thomson, M. D. F.R.S. 

 Ed. Communicated by Chari<es ILixcHEXT, Ulsq., 

 F. E. S.* 



vJ'XALIC acid, from the united testimony of Ehrhart, 



„ ,. ., Heimbstadt, and Westrumb, appears to have been disco- 



Qxalic acid . . 



discovered by veved by Scheele; but it is to Bergman that we are indebted 



for the first account of its properties. He published his dis- 

 sertation on it in 1776, and since that time very little has 

 been added to the facts contained in his valuable treatise. 

 Chemists have chiefly directed their attention to the forma- 

 tion of that acid, and much curious and important infor- 

 mation has resulted from the experiments of Hermbstadt, 

 Westrumb, Berthollet, Fourcroy, Vauquelin, &c. but the 

 properties of tlie acid itself have been rather neglected. 

 My object in the following pages is not to give a complete 

 paid'to'its'lJio- history of the properties of oxalic acid, but merely to state 

 penies. ^|jg vesult'of a set of experiments, undertaken with the view 



of ascertaining different particulars respecting it, which 1 

 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 por- 

 rlir-^m!^ .*f,fin tion of water, for when moderately heated they effloresce 

 and lose a part of their weight, which they afterwards reco- 

 ver 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 



Littleaitcntion 



crystallization. 



• Philos. Trans, for 1807, p. G;?. 



not 



