Chemical Science. 179 



The acid malate of ammonia was then decomposed in the manner 

 adopted by MM. Liebeg and Woehler, with the hippuric acid*. It 

 gave azote and carbonic acid in the proportion of 1 : 8, indicating 

 four atoms of carbon in the acid. The hydrogen was determined 

 by burning the dry malate of zinc with oxide of copper, and collect- 

 ing the water by chloride of calcium. The results came out as 

 4 atoms carbon, 24 ; 2 hydrogen, 2; 4 oxygen, 82; =58: but as 

 this was too high, as compared to the conclusions respecting the 

 equivalent number, and as it was the same with the composition of 

 dry citric acid, excess of hydrogen was suspected ; and as a trace of 

 water in the salt used would account for this excess, other experi- 

 ments were made with the anhydrous malate of silver. This salt 

 gave little more than one atom of oxygen, and the composition of 

 malic acid may therefore be considered as follows : 



4 atoms carbon . . 24 



1 hydrogen . . 1 



4 oxygen . . 32 



Equivalent number . 57f 



14. ULMIN, OR ULMIC ACID, AND AZULMIC ACID. 



The following points relative to the history of ulmin are abstracted 

 from a thesis by M. P. Boullay on this subject. This substance 

 derives its importance from the numerous circumstances which give 

 rise to it, and the daily conversion of numerous vegetable matters, 

 especially those in wood, into it. Its existence in vegetable earth, in 

 manure, and in the sap of plants, shews the important part which it 

 performs, and it is probably the most valuable compost known. It 

 occurs in enormous quantities in brown earth, turf, &c., and Hol- 

 land probably owes the superiority of its agricultural productions 

 to the quantity which it naturally possesses. 



M. Boullay has considered it as an acid, and gave it a corre- 

 sponding name, because of its power of combining with bases. It 

 was first found by Vauquelin in an exudation from the elm tree ; M. 

 Braconnot formed it artificially. It is produced in the distillation of 

 wood in soot, and may be formed by the action of sulphuric and 

 muriatic acids upon many vegetable substances. 



Ulmic acid differs from the substances produced by the action 

 of air or oxygenizing bodies, on extracts, tannin, gallic acid, or 

 gallates, both by its colour and solubility in alcohol. It is more 

 probable, from the properties of the resulting substance, that when 

 gallic acid or the gallate of ammonia is exposed to air, a new sub- 

 stance, not sufficiently examined, is produced. 



The composition of ulmic acid is the same as that of dry gallic 

 acid, but it has a much feebler saturating power ; its equivalent 

 number is to that of gallic acid as 5 : 1. It has been analysed by 



* Quart. Jour, of Science, vol. vii. p. 424. f Ann. de Chim. xliii. 259. 



N 2 



