22 COMBINATIONS OF OXALIC ACID. 



time the top of the retort became lined with fine acicular 

 crystals of oxalic acid. 



lii this state the acid is very light, very white, and a little 

 attractive of the moisture of the atniosphere. If put into 

 water, it becomes pasty before it dissolves. 

 Oxalate of From my exj.'eriments it appears, that this sublimed acid 



luiiecim jg jjg dry as that which exists in the oxalate of lime. I 



this weighed 3°42 gram., aissolved them in water, neutralized 



them with ammonia, precipitated with muriate of lime, and 

 carefully washed the precipilate. To collect and weigh it» 

 1 threw it on a filter, which was placed on another filter of 

 the same weight. I then dried them gently, till I could 

 easily separate the precipitate, which I afterward exposed 

 to the heat of a water bath. It weighed 5*374 gr. : but the 

 weight of the inner filter exceeded that of the outer by 

 0086 of a gr. ; fo that 1 had 5*4G gr. of oxalate of lime, 

 ivhich, according to the analysis I have given above, con- 

 tained 3*385 gr. of acid, being nearly equal to the quantity 

 of sublimed acid I employed*. 



A second experiment confirmed these results. 

 ris msrlHbilitv Before I undertook the subsequent experiments, I satis- 

 <,xamiaed. ' ficd myself, that the oxalate of lime was sufficiently inso- 

 luble, to indicate with precision the quantity of acid con- 

 tained in a compound. 5 gr. [77 grs] of lime-water neutra- 

 lized by muriatic acid were diluted with 400 gr. of distilled 

 t^ater ; and in one twentieth of this oxalate of ammonia 

 produced a precipitate, that could be perceived without 

 hesitation. This was more than sufficient for analyses of 

 iiuch a nature. 



But the least excess of acid dissolves a large quantity of 

 this salt ; hence I have always taken care to employ it with 

 neutral compounds. 



Crystallized oxalid acid. 



Quantity of To repeat the experiments of Dr. Thomson, crystallized 



real .ic.d m oxalic acid always appeared to me more commodious than a 



crystal of ^ i • • i i • j • , 



oxalic aciti solution of this acid : and in order to ascertain the quantity 



of real acid contained in what I was to employ, I neutralized 



• According to the proportions assigned by Dr. Thompson, it con- 

 ts^ined 3412, which comes very near indeed to ihe quantity used. C. 



