260 GELATIN1Z ATION OF TINCTURE OF KINO. 
lution, from which water precipitates nothing, but which red- 
dens litmus, and deposits a copious precipitate when potash, 
ammonia, or lime-water is dropped in. From these and other 
experiments (says Pereira,) I infer that Botany Bay kino con- 
sists principally of pectin and tannic acid." 
It is well known, that alcohol added to a solution of pectin, 
causes it to assume the form of a consistent jelly; but this 
result sometimes does not ensue until after an interval of 
several days, which in some degree seems to correspond 
with the phenomena observed in tincture of kino. On the 
presumption, therefore, that the gelatinization of this tincture 
depends on the presence of pectin, rectified spirit has been 
used in its preparation instead of proof spirit, with the view 
of obviating that result, pectin being insoluble in rectified 
spirit. This substitution, however, has not been found to ef- 
fect the intended object, as the tincture prepared with recti- 
fied spirit is subject to the same change as that made with 
proof spirit. 
There is one fact connected with the change effected in 
tincture of kino, which, although incidentally noticed by Pe- 
reira, appears not to have been sufficiently taken into account 
in explaining the cause of the gelatinization. It has been ob- 
served that the tincture, as it assumes the form of jelly, loses 
in a great measure its astringent property. On first directing 
my attention to this subject, I thought it probable this might 
arise from the insolubility of the gelatinous mass; and find- 
ing allusion made, in a paper by Berzelius, in the Annales 
de Chimie et de Physique, for 1828, to an insoluble combi- 
nation of pectic acid and tannin, which he and others had 
met with in the extract of nutgalls, and more especially in 
the extract of oak bark, I concluded that the gelatinous tinc- 
ture of kino would prove to be a compound of a similar na- 
ture. Both pectin and tannic acid are susceptible of such a 
variety of changes, under the influence of different agents, 
that some modification of their characters might be antici- 
pated in such a compound. Thus pectin is converted into 
pectic acid by the action of alkalies or strong acids, and 
