226 HOW CROPS FEED. 
ulmic acid. By boiling it with caustic soda or potash-lye, 
it is converted without change of composition into ulmic 
acid. 
On gently heating sugar with dilute hydrochlorie acid, 
a brown substance is produced, which appears to be iden- 
tical with the ulmic acid obtained from peat. 
Mumic Acid and Humin. — By treating black humus 
with carbonate of soda as above described, it is separated 
into humic acid and humin*, which closely resemble ulmic 
acid and ulinin in all their properties—possess, however, a 
black color, and, as it appears, a somewhat different com- 
position. 
Humic acid and humin may be obtained also by the 
action of hot and strong hydrochloric acid, of sulphuric 
acid, and of alkalies, upon sugar and the other members 
of the cellulose group. 
Composition of Ulmin, Ulmic Acid, Humin, and Humic 
Acid.—The results of the analyses of these bodies, as ob- 
tained by different experimenters and from different 
sources, are not in all cases accordant. Either several dis- 
tinct substances have been confounded under each of the 
above names, or the true ulmin and humin, and ulmic and 
humic acids, are linble to occur mixed with other matters, 
from which they cannot be or have not been perfectly 
separated. 
Mulder (Chemie der Ackerkrume, 1, p. 322), who has 
chiefly investigated these substances, believes there is a 
group of bodies having in general the characters of ulmin 
and ulmic acid, whose composition differs only by the ele- 
ments of water,} and is exhibited by the general formula 
C,, H,, O,, + nH,0O, 
in which nH,O signifies one, two, three, or more of water 
* See note on page 225. 
+ In a way analogous to what is known of the sugars. (H.C. G., p. 80.) 
