186 Miscellaneous Intelligence. 



r 9. ON OXALIC ACID. (By M. Gay Lussac.) 



Oxalic acid, when heated, is well known to be partly volatilized 

 and partly decomposed into carbonic acid and a combustible gas. 

 Wishing to know more particularly the nature of these gases, M. 

 Gay Lussac heated some very pure crystals of the acid in a retort: 

 at 209 F. they fused ; at 230 water and elastic fluids were disen- 

 gaged, and the latter increased as the water passed away ; at 

 248 266 the disengagement was very rapid, and continued 

 until all the acid was decomposed*. The gas was a mixture of six 

 volumes of carbonic acid and five volumes of carbonic oxide, the 

 proportion being nearly the same during the whole decomposition. 



This easy decomposition was unexpected ; for oxalic acid is con- 

 sidered as a stable compound among vegetable acids. The utility 

 of sulphuric acid in the ordinary mode of decomposition was there- 

 fore suspected, and it was found, in fact, that when mixed with that 

 acid, still a temperature of 230 240 was required. But there is 

 this important difference, that in the latter case the gas evolved 

 consists of equal volumes of carbonic acid and carbonic oxide. 



This difference led to the suspicion that some other substance was 

 formed during the decomposition. On examination, it was found 

 that the water which passed over was acid, and that it was so from 

 the presence of formic acid. At first this acid appears in small 

 quantity, but it comes over more and more concentrated, and 

 towards the end of the operation the product has a very penetrating 

 odour and sharp taste. Supposing that the sixth or missing vo- 

 lume of carbonic oxide with water forms this acid, then twelve pro- 

 portions of oxalic acid should form one of formic acid, and this ap- 

 peared to be the case. 



It is evident that the hydrogen has been given to the formic acid 

 by the water, and not by the oxalic acid, for then the carbonic acid 

 and oxide should have been in equal volumes ; besides, it is a 

 necessary consequence of the experiments of MM. Dulong and 

 Dobereiner. If the decomposition is not carried on too rapidly, it 

 is total, no oxalic acid being volatilized. 



These effects render it more imperative, M. Gay Lussac thinks, 

 that oxalic acid should not be separated from the two other com- 

 pounds of carbon and oxygen, i. e. carbonic acid and carbonic oxide, 

 It may be ranged amongst those acids into which two equivalents 

 of the radical enter, and the name which may be applied to it is 

 hypocarbonic acid ; but M. Gay Lussac does not press the adoption 

 of this name at present f. 



10. Dr. TURNER ON THE VOLATILITY OF OXALIC ACID. 



Dr. Turner having lately examined the volatility of oxalic acid, finds 



* See next page. f Annales de Chimie, xlvi. 218. 



