74 Intelligence and Miscellaneous Articles. 



SCHEELE's ARTIFICIAL MALIC ACID — OXALHYDRIC ACID. 



In our Number for March last we have briefly noticed M. Gue- 

 rin's experiments on artificial malic acid. The author has continued 

 his experiments, and the results are, that the acid produced by the 

 action of nitric acid and gum differs from vegetable malic acid, and 

 for a reason which will presently appear, the author has called it ox- 

 alhydric acid. We have given the author's original mode of prepara- 

 tion, but he appears to have improved it, and now states it as follows : 

 Mix one part of gum arabic with two parts of nitric acid of density 

 1"339, diluted with one part of water ; heat the mixture in a retort, 

 the capacity of which is equal to four times that of the mixture, 

 with a tubulated receiver adapted to it ; apply heat gently until the 

 gum is dissolved. When nitrous vapours appear, remove the fire, 

 and a copious disengagement of nitric oxide ensues. When this 

 ceases, boil the liquor slowly for an hour, dilute it with four times 

 its weight of water, and saturate with ammonia; then add a solution 

 of nitrate of lime to precipitate the small quantity of oxalic acid 

 formed ; the reddish yellow liquor being filtered, precipitate it with 

 acetate of lead; the precipitate is to be thrown upon a filter and 

 washed till the liquor ceases to blacken sulphuretted hydrogen ; 

 this precipitate is afterwards decomposed by a current of washed 

 sulphuretted hydrogen gas, or by sulphuric acid diluted with six 

 times its weight of water. 



The acid thus obtained is of a yellow colour; it is to be evapo- 

 rated with a gentle heat, and when sufficiently concentrated, to be 

 neutralized by ammonia, and again evaporated till crystallization 

 begins ; the crystals, of a very deep brown colour, are to be purified 

 by animal charcoal. The colourless liquor is to be precipitated by 

 acetate of lead, and again treated, either with sulphuretted hy- 

 drogen or diluted sulphuric acid, as already directed. The solu- 

 tion of the acid thus procured is to be evaporated nearly to the 

 consistence of a syrup, and the evaporation is to be finished in 

 vacuo. 



The properties of the acid are, that it has the consistence of a 

 strong syrup, is colourless, of a taste much like that of oxalic acid. 

 Its density is 1416. It dissolves in water and in alcohol in all pro- 

 portions. In aether, whether cold or boiling, it dissolves sparingly; 

 it is very deliquescent, precipitates lime, barytes, and strontia water, 

 but the precipitates are redissolved by an excess of acid. It preci- 

 pitates the salts of lead and of silver in bulky colourless flocks. By 

 long exposure crystals of oxalhydric acid were obtained, which 

 had properties similar to those of the syrupy solution. 



The following are the comparative constitutions of oxalhydric 

 acid by M. Guerin, and vegetable malic acid by Liebig; 

 Oxalhydric acid. Malic acid. 



Oxygen 6 atoms .... 5 



Carbon 4 — . . . . 5 



Hydrogen 6 — . . . . 2 



One part of oxalhydric acid being mixed with three parts of nitric 

 acid, in a month there were formed, without employing heat, fine 



