OXALIC ACID. 41 



OXALIC ACID. C 2 O 3 .HO. 



Chemical Relations. 



Properties. This acid crystallises with 3 atoms of water in 

 oblique rhombic prisms, is devoid of smell, has a sharp acid taste, 

 and effloresces on exposure to the air, losing 2 atoms of water 

 and becoming disintegrated into a white powder ; on heating it care- 

 fully to 150 or 160, it sublimes undecomposed in acicular crys- 

 tals ; but at 170 (or if the crystallised acid be rapidly heated to 

 155), it becomes decomposed into carbonic oxide and carbonic 

 acid, a little formic acid, and water ; it dissolves in 8 parts of cold 

 and 1 part of boiling water, and in 4 parts of spirit of wine ; its 

 solutions redden litmus strongly. On boiling oxalic acid with solu- 

 tion of oxide or chloride of gold, carbonic acid is evolved, and the 

 gold is precipitated in the form of extremely fine black powder. 

 Treated with concentrated sulphuric acid, it becomes decomposed 

 into carbonic oxide and carbonic acid, and effects no change in the 

 colour of the sulphuric acid. 



Composition. In accordance with the above formula, this acid, 

 which cannot exist in the free state without water, contains in 100 

 parts : 



Carbon 2 atoms = 26-667 



Hydrogen 3 = 53*333 



Water 1 = 20-000 



100-000 



The atomic weight of the hypothetical anhydrous acid= 450*0 ; 

 its saturating capacity = 22*222. 



In reference to the history of this acid, we may observe that 

 while some chemists regard it as the oxide of an oxygenous radical, 

 oxalyl=C 2 O 2 , in consequence of the preponderance of its acidity 

 over that of carbonic acid, others regard it as a hydrogen acid 

 =C 2 3 .H. 



Combinations. Oxalic acid combines with alkalies in three pro- 

 portions, in which the oxygen of the base is to that of the acid as 

 1 : 3, 1 : 6, and 1:12 respectively. These salts are soluble in 

 water, but all other oxalates are insoluble, or only very slightly 

 soluble, in that fluid; none of the oxalates are soluble in alco- 

 hol. These salts do not char when heated. The combinations of 

 oxalic acid with the more easily reducible oxides, yield carbonic 

 acid and the reduced metal (thus, for instance, CoO.C 2 O 3 =:2CO 2 

 -f Co) ; while those with less easily reducible bases evolve carbonic 

 oxide gas, and are converted into carbonates. 

 Omlate of Amminia, neutral oxalate of oxide of ammonium, 



