GELATINIZATION OP TINCTURE OP KINO. 263 
by exposing sawdust and hydrate of potassa, moistened with 
water, to a moderate heat. By this last process, ulmate of 
potassa is formed, which is soluble in water, and from 
which ulmic acid may be precipitated by either of the strong 
acids. 
Ulmic acid, thus obtained, is similar in color to the gela- 
tinous tincture of kino. It is insoluble in water, alcohol, and 
ether; but soluble in solution of caustic potash or of ammo- 
nia. The alkaline solutions, on the addition of chloride of 
calcium, yield a reddish-brown precipitate, which is soluble 
in alcohol. They yield a black precipitate with sulphate of 
iron, but no precipitate with gelatine. The ammonia cal 
solution yields a deep red precipitate with nitrate of 
silver. 
I have not yet submitted the insoluble product of the gela- 
tinous tincture to an ultimate analysis, but the result of its 
examination by reagents, appears to be so conclusive, as to 
leave but little doubt of its identity with ulmic acid. There 
are several points, connected with the conversion of the 
tannin contained in tincture of kino, into this substance, 
which open a wide field for further investigation, and will 
add to the interest which has already been felt, in what may 
be called the tannin family. The difference which exists 
in the properties of this body as obtained from different 
sources, and the changes which so readily take place in the 
several kinds of tannin, have frequently attracted the atten- 
tion of chemists. In a paper on tannic acid by Berzelius, to 
which I have already alluded, he observes that "the tannin 
contained in kino, differs greatly from that obtained from 
nutgalls, cinchona bark, or catechu " that it has so great a 
tendency to form extractive, that its solution becomes turbid 
from contact with the air, and deposits a transparent red sub- 
stance." The organic matter to which the term extractive 
is thus applied, appears to be but ill defined and imperfectly 
understood. According to Dr. Kane, it consists of that por- 
tion of a plant which has been dissolved out by means of wa- 
ter, and partly decomposed during the process of inspissatior*. 
