Action of Tannin on Organic Salifiable Bases, fyc. 229 
the vegetable alkali, but has no action on the calcareous tan- 
nate. It will be found that the tannin had produced no modifica- 
tion in the alkali during its combination with it, and if care 
be taken, very little of it is lost during these successive manipu- 
lations. In operating in the above manner on diluted solu- 
tions, acidulated by one or two drops of sulphuric acid, of 
quinine, cinchonine, morphine, codeine, &c, I was always 
able to obtain them again in their original quantities, and 
without any change in their properties; hence, it is probable 
that all the other vegetable bases are capable of combining 
w T ith tannin without undergoing any modification. 
I have said that when a solution of a vegetable organic salt 
is treated by tannic acid, an abundant white precipitate is 
produced, scarcely soluble in water, this precipitate must be 
considered as an acid or bitannate. I prepared in turn this 
salt of the thirteen alkaloids as noticed in the preceding table, 
but as they closely resemble each other in their prominent 
characters, I will not describe them in detail, but will merely 
indicate their general properties. 
General characters of the organic bitannates. — All the or- 
ganic bitannates are white, and caseiform, when in the state 
of hydrates, scarcely soluble in water, but somewhat so when 
heat is used; they then form a styptic liquid, which on cool- 
ing becomes turbid and affords a brown substance resembling 
resin. When dried in the air, they are reduced to a white 
powder, which has a musty smell; on exposure to heat, they 
melt into a brown resinous mass, which is flexible whilst hot, 
but brittle and friable when cold. 
These compounds are soluble in some of the diluted acids 
and in boiling alcohol at 32° or even 28°; this latter solution 
reddens litmus paper; its taste is rather styptic than bitter; 
none of them appear capable of crystallization. 
When exposed in a bell glass containing two-thirds of 
oxygen, in a mercurial trough, for some weeks, the most part 
of them become very soluble in water, and strike a blue co- 
lour with the persalts of iron. This modification, which takes 
place without much diminution of the gas, appears to depend 
on the formation of gallates, and is analogous to that which 
