COMBINATIONS OF OXALIC ACIB. 31 



Oxalate of magnesia. 



This salt is completely similar to oxalate of lime in many Oxalate of 

 ,,,.., , , naagnefia. 



respeccs. 1 analysed it in the same manner, because the 



little solubility of lOagnesia did not admit of neutralizing a 



given weight of the acid by this alkali. 



10 gr. of this salt, dried on a water-bath till its weight was 

 no longer diminished by the heat, were exposed to a 

 strong heat in a platina crucible, and yielded 2*86 gr. of 

 magnesia, containing 0*125 of agr. of carbonic acid. 



We have therefore for the proportions of oxalate of 

 magnesia 



27'35 magnesia, Its component 



72'65 oxalic acid. ^*' *' 



100. 



This gives 265'6 of oxalic acid to 100 of magnesia. 



The oxalate of magnesia is extremely little soluble ia Sulphg^ 

 water, and in an excess of its acid. Yet, when a solution of ^^ magnesia 

 sulphate of magnesia is mixed with one of oxalate of ammo- diately pte- 

 nia, no precipitate is produced. Dr. Thomson, in relating cipitated by 

 this fact, seems to oppose it to the principle, that the sepa- n^^^nia bm 

 ration of salts is determined by the force of cohesion : but I slowly 

 have observed, that letting the mixture stand some time is ®'^**°^P"^* 

 sufficient, to precipitate the oxalate of magnesia completely, 

 without our being capable of redissolvingit. 



Such are the proportions that result fronu my analyses of Comparison of 

 the oxalates. Some of them differ from those, which Dr, the lesults. 

 Thomson has given* ; so that it was not till I had repeated 

 them with all the care, of which 1 was capable, that I placed 

 contidence m my results. What appears to me to confirm 

 theiu is, that they agree much better with the capacities of 

 the aiiiaiis ior saturating acids already admitted. 



For the &ake of a more ready comparison, I shall here 

 give a tabular view of my analyses and those of Dr. 

 Thomson ; and 1 shall add, in tne last column, the propor- 



• I believe, the principal difference between Dr. Thomson's analyses Dr. Thomson 

 and mine arose from that gentleman, certainly a very expert chemist, used loo small 

 having operated with too small quantities, quantities. 



tions 



