ORGANIC MATTERS OF THE SOIL. 227 
Ulmic acid from sugar has the following composition in 
109 parts: 
Carbon, 67.1 
Hydrogen, 4.2 
Oxygen, 28.7 
100.0 
which corresponds to C,, H,, O,, H,O. 
Mulder considers that in. the same manner there exist 
various kinds of humic acids and humin, differing from 
each other by the elements of water, all of which may 
be represented by the general formula C,, H,, O,, nH,O. 
Humic acid and humin from sugar, corresponding to 
C,, H,, O,, + 3H,O, have, according to Mulder, the fol- 
lowing composition per cent: 
Carbon, 64 
Hydrogen, 4 
Oxygen, 32 - 
100 
Apocrenic and Crenic Acids.—In the acid liquid from 
which ulmic or humic acid has been separated, exist two 
other acids which were first discovered by Berzelius in 
the Porla spring in Sweden, and which bear the names 
apocrenic acid and -crenic acid respectively. By adding 
soda to the acid liquid until the hydrochloric acid is neu- 
tralized, then acetic acid in slight excess, and lastly solu- 
tion of acetate of copper (crystallized verdigris) as long 
as a dirty-gray precipitate is formed, the apocrenic acid is 
procured in combination with copper and ammonia. From 
this salt the acid itself may be separated * as a brown, 
gummy mass, which is easily soluble in water. Accord- 
ing to Mulder it has the formula C,, H,, O,, + H,0, or, 
in 100 parts, 
* By precipitating the copper with sulphuretted hydrogen. 
