Chemical Science. 4 1 5 



The residue was very white ; being dissolved in water, and saturated 

 by nitric acid, hydrocyanic and carbonic acid were disengaged; 

 nitrate of lime then produced an abundant precipitate of oxalate 

 of lime. Gelatine gave a similar result. Indigo gave no oxalic 

 acid. 



Carbonate of potash used instead of caustic potash gave no oxalic 

 from tartar; nor did lime and starch produce any oxalic acid. 

 Soda may be used instead of potash. 



From these experiments, it appears that a great number of animal 

 and vegetable substances, acted upon by caustic potash or soda, are 

 transformed into oxalic acid. It is to be remarked that the forma- 

 tion of this acid precedes that of carbonic acid, and precisely under 

 the same circumstances, as when sulphur and potash, for instance, 

 produce hyposulphurous and sulphuric acids. Thus a vegetable sub- 

 stance, heated moderately with potash, gives oxalic acid, but when 

 more strongly heated, carbonic acid. 



As very different substances produce oxalic acid, it is necessary 

 that other products should be formed. Many bodies evolve hydro- 

 gen which may come from themselves, or from the water they con- 

 tain, and afterwards carbonic acid. Animal matters, besides these 

 two products, give also ammonia and cyanogen. Water must also 

 be formed with both animal and vegetable substances. These pro- 

 ducts, or some of them, are sufficient to explain in general the 

 formation of oxalic acid, but in some particular cases there ought 

 to be other products obtained. Thus tartaric acid gives no sensible 

 portion of hydrogen, and yet its composition being 2J proportions 

 of hydrogen, 4 of carbon, and 5 of oxygen, we cannot explain its 

 transformation into oxalic acid by the occurrence of any of the 

 known products. 



In fact, during the operation, the mixture remains perfectly white. 

 If all the carbon entered into the oxalic acid, it would require 6 pro- 

 portions of oxygen, and consequently water ought to be decom- 

 posed to furnish 1 proportion. If only so much oxalic acid were 

 formed as is proportional to the oxygen in the tartaric acid, then 

 |of a proportion of carbon would remain, which might form a 

 particular compound with the hydrogen ; and for 1 proportion of 

 tartaric acid, l£ of oxalic acid would be produced. In place of this 

 last quantity, 1 have obtained H oxalic acid, but I have not dis- 

 covered any hydrogenated compound. Finally, it was possible that 

 a peculiar acid had been formed by the carbon, oxygen, and 

 hydrogen. This point deserves particular examination, and I should 

 have undertaken it in the vacations, if I had had time, but hope 

 to resume the subject shortly. 



I shall conclude by describing a very elegant method of trans- 

 forming tartar into oxalate of potassa. It consists in dissolving 

 rough tartar in water, with a proper quantity of potash or soda, and 

 making the solution pass by means of a pump in a continual current 

 through a thick tube of iron or bronze heated to 400° or 450° F. 



