20 



Oxalate of am- 

 monia. 



ON OXALIC ACID. 



excess of acid, and of forming a superoxalate. I have not 

 tried the experiment. 



7. Oxalate of ammonia is the most important of iill i:he 

 oxalates, being very much employed by chemists to detect 

 the presence of lime, and to separate it from solutions, it 

 crystallizes in long trasparent prisms, rliomboidal, and 

 terminated by dihedral summits. The lateral edges are 

 often truncated, so as to make the pri.-m 6 or 8-sided. 

 Sometimes the original faces of the prism are near'v ef- 

 faced. 



The taste of this salt is bitter and unpleasant, somewhat 

 like that of sal ammoniac. At the temperature of 60% 

 1000 grains of water dissolve only 45 grains of this salt. 

 Hence, 1000 grains of saturated solution of oxalate of am- 

 monia contain oidy 43-2 grains of this salt. The specific 

 gravity of this solution is r0186. As it may be useful to 

 know the weight of this salt contained in solutions of dif- 

 ferent specific gravities, I have thought it worth while to 

 construct the followin<r table : 



Specific gravity 

 of solutioa of 

 oxiilate of am- 

 monia. 



Weight of oxabte 



Specific gra- 



Weight of oxalate 



Speiific gra- 



of ammonia in 100 



vity of the >o-\> 



of ammonia in 100 



vity of theso- 



])arts of the soiution 



lutionatCO° j 



parts of the solution 



iutionatGO*'. 



4-32 



■ 

 1-0186 



1*5 



1-0075 



4- 



1-0179 



1- 1-0054 



3-5 



1-0 160 



0-5 1-0030 



3- 



1-0142 



0-4 1-0024 



2-5 



1-0120 



0-3 1-0018 



2* 



0-001)5 



0-2 1-0012 

 I 0-1 1-0006 



Method of de- 8. To determine the composition of these sails, I took 



termining the ggyen different portions of a diluted oxalic acid solution, 

 combustion of , ... ,^^ ■ 1 ... _, . „ , 



th^ oxalates, each weigh mg 100 grains, and containing 7 grams of real 



oxalic acid. To each of these portions I added respectively 

 potash, soda, ammonia, barytes water, strontian water, and 

 lime water, till it ceased to produce any change. The li- 

 quid was then evaporated to dryness, and the residue, after 

 ^eing well dried on the steam bath, was weighed. Each 

 of these salts contained 7 grains of acid ; the additional 



weiijht 



