Natural-Philosophical Collections. 383 



This new fact, described by M. Dumas, shows how frequent, in the course of 

 geological accidents, are the phenomena which give rise to the accumulation of 

 gas in the cavities of mineral substances, and how varied are the substances upon 

 which these phenomena have been exerted. M. Dumas has endeavoured to re- 

 produce salt having the power of decrepitating in water like that described — 

 Revtte Eiwyc. xlvi. 243. 



On a new Acid contained in the Urine of Herbivorous Animals ; by M. LiE- 



BEG The following abstract is made from M. Liebeg's paper, published at 



length in the Annales de Chimie, xliii. 188. Fourcroy and Vauquelin discover- 

 ed a particular acid in the urine of certain animals, which they took for benzoic 

 acid, and which appears to be the same as the one to be described. When the 

 urine of the horse is mixed with excess of muriatic acid, a yellow-brown crystal- 

 line precipitate is gradually formed, having an unpleasant odour, which cannot be 

 removed by simple washing with water. It is to be boiled with quicklime an4 

 water, the liquor filtered, a solution of chloride of lime added, until all urinous 

 odour ceases, and then animal charcoal added, until the liquid which passes the 

 filter is colourless. This liquid, whilst hot, is to be mixed with great excess 

 of muriatic acid, and left to cool. There separate prismatic crystals two or 

 three inches long, of a shining white colour, translucent, and which differ from 

 benzoic acid, not only in the forms of its crystals, but by its smaller degree of in- 

 solubility in water, by the diiference of its salts from the benzoates, and by its 

 composition including azote. It fuses by heat, then is decomposed and becomes 

 black, a crystalline sublimate rises, an odour of bitter almonds is perceived, and 

 much charcoal is left. Being mixed with four times its weight of hydrate of 

 lime and heated, much ammonia is disengaged. 



Being obtained from the urine of the horse principally, it has been distinguish- 

 ed by the term hippuric acid. Sulphuric acid heated to 248° F. dissolves it 

 without change, water precipitates it ; a higher heat enables the acid to decom- 

 pose it, and ultimately white crystals sublime. It dissolves also in nitric acid, 

 and by heat is then decomposed. It is soluble in hot muriatic acid, but crystal- 

 lizes out upon cooling. Aqueous solution of chlorine does not act upon it, but 

 boiling with much chloride of lime decomposes it entirely. 



When burnt very carefully by means of oxide of copper, it gave a mixture of 

 carbonic acid and azote in the proportions of 100 to 5. This result appearing 

 important, was confirmed by another mode of investigation, namely, by burning. 

 Dot the acid, but its ammoniacal salt, by means of peroxide of copper, and ob- 

 serving the relation of the azote to the carbonic acid. The oxalate pf ammonia 

 burnt in this way yields 1 volume of azote and 2 of carbonic acid, the latter in- 

 dicating so many volumes, i. e. 2 of carbon. The acid hippurate of ammonia so 

 burnt gave 2 of azote and 27 of carbonic acid, confirming the result above. By 

 other analytical processes the quantity of water given by 0.300 parts of the acid 

 when burnt, was found to be 0.180, and from these and other data the following 

 composition was made out : 



Azote . . . .046 or theoretically, 14 1 atom. 



Carbon . . . .393 . . 120 20 atoms. 



Hydrogen . . .031 . . 10 10 



Oxygen . . . .155 . . 48 6 



.625 192 



The mean result of experiments on its atomic weight was 197. In the hip- 

 purate of lead, 100 parts of the acid combine with 55.31 oxide of lead, and the 

 crystallized salt contains besides 25. G4 of water. The hippuric acid, when cry- 

 stallized, is anhydrous and requires 600 parts of water at 32° for its solution. 



Hippuric acid easily dissolves most of the metallic oxides. The soluble com- 

 VOL. II. ^ 3d 



