262 GELATINIZATION OF TINCTURE OF KINO. 
a slightly-colored solution, neutral to test paper, but yielding 
precipitates characteristic of tannic acid, with gelatine, sul- 
phate of copper, and nitrate of silver. A black precipitate 
was formed on the addition of protosulphate of iron. 
The insoluble residue, left after treating the gelatinous sub- 
stance with boiling water, was now boiled in solution of am- 
monia, in which, as well as in solution of caustic potash, it 
was found to be perfectly soluble, forming a deep brown so- 
lution. The solution with ammonia being boiled so as to 
expel the excess of ammonia, and chloride of calcium being 
added, afforded a copious precipitate of a reddish-brown co- 
lor. This precipitate was washed with diluted muriatic acid, 
and collected on a filter. It was insoluble in water with boil- 
ing, and equally so with the addition of sugar. Alcohol dis- 
solved it entirely, and formed a solution which showed no 
disposition to gelatinize. It is very evident, therefore, that 
the precipitate thus obtained was not pectic acid, and that 
neither pectin nor pectic acid was present in the gelatinous 
mass. 
The solutions formed with ammonia and with potassa, 
throw down precipitates on the addition of nitric, sulphuric, 
or muriatic acid; they afford a deep, black precipitate with 
sulphate of iron, but no precipitate with gelatine. The am- 
moniacal solution affords a deep red precipitate with ni- 
trate of silver* 
These reactions correspond so exactly with those of ulmic 
acid, that I am disposed to consider the gelatinous matter 
formed in tincture of kino, to be identical with, or very ana- 
logous to that substance. 
The class of bodies to which the terms ulmine, ulmic acid, 
and humus, are applied, have not been much studied until 
very lately, when more attention has been directed to them 
in consequence of their supposed influence upon the fertility 
of soils. These bodies, as generally met with, are produced 
either by the decomposition of vegetable matter in the soil, 
or as the result of disease in plants. They may also be pro- 
duced by the action of dilute acids and heat upon sugar, or 
