Dr. Turner on the Volatility of Oxalic Acid. 163 



subliming acid, as the beat is more or less intense, suffers de- 

 composition ; a change immediately indicated by the appear- 

 ance of water. 



The facts already mentioned leave little doubt of sublimed 

 oxalic acid consisting of 36 parts or one equivalent of the 

 anhydrous acid, and 9 parts or an equivalent of water. The 

 correctness of this opinion was proved by analysis, the oxalic 

 acid being precipitated with lime, and its quantity inferred in 

 the usual manner by decomposing the resulting oxalate of 

 lime. The sublimed acid, also, is readily decomposed by con- 

 centrated sulphuric acid, yielding abundance of gas, which con- 

 sists of exactly equal measures of carbonic oxide and carbonic 

 acid. When neutralized with potash and ammonia it yields 

 crystals similar to the well-known oxalates of those alkalies; 

 and the crystals obtained from a solution of the sublimed acid 

 in pure water, were measured by Mr. Miller of St. John's Col- 

 lege Cambridge, and found identical with the crystals of the 

 common acid. These facts leave no doubt concerning the 

 nature and constitution of the sublimed acid. 



Before concluding this notice, I may add a few remarks on 

 the solubility of ordinary oxalic acid in water, concerning which 

 the statements of different authors are very discordant. The 

 solvent power of water increases rapidly with the temperature. 

 A hot solution of oxalic acid was set aside for twenty-four 

 hours, when the clear liquid, kept at the temperature of 50 

 Fahr., was decanted from the crystals which had been de- 

 posited. This solution consisted of one part of crystallized 

 acid and about 15 '5 of water. The experiment was repeated 

 by putting the pulverized crystals into water at 50, agitating 

 repeatedly during twenty-four hours, and then decanting the 

 solution from the undissolved acid. The ratio of the ingre- 

 dients was almost exactly the same as that above stated. Si- 

 milar observations were made with water at 57Fahr., of which 

 9*5 parts dissolve one of the crystallized acid. 



Crystallized oxalic acid dissolves in almost an unlimited 

 quantity in water kept at 212 by immersion in boiling water. 

 If the acid solution is kept boiling by the direct application 

 of fire, the temperature rises considerably above 212, and the 

 quantity of the crystallized acid dissolved is then unlimited. 

 This is not surprising; since the crystals fuse in their water 

 of crystallization at about 220 Fahr. 



I may also add the following observations on the degree of 

 permanence of crystallized oxalic acid. When the crystals 

 are kept for some hours under a bell-jar, with quick-lime, at a 

 temperature not higher than 50 or 55, they contain all their 

 water of crystallization, consisting of one equivalent of real 



Y 2 oxalic 



