424 Dr. Stenhouse on some 
however, it reddens it strongly. It consists of at least two 
substances, one of which only is soluble in hot alcohol, so that 
they may be easily separated by this means. They both 
dissolve very readily in alkalies, and decompose the carbonates 
when assisted by heat. When saturated with ammonia and 
rendered neutral by digestion, they give dark brown precipi- 
tates with salts of silver, copper, iron, lead, barytes and lime. 
Their alkaline solutions are dark brown, and they are com- 
pletely precipitated by acids. These humus-like substances 
are produced by the action of the acids on the tannin only, 
for on boiling gallic acid with concentrated muriatic acid for 
several hours I did not succeed in obtaining even a trace of 
them. I am at present engaged in their further investigation. 
Valonia.—The next of the astringent matters examined 
was valonia. It is the acorn of the Quercus Aigilops, and is 
imported in considerable quantities from the Levant for the 
use of the tanners. The dried extract of valonia prepared 
like that of sumach, when destructively distilled, gave no indi- 
cation of pyrogallic acid. Valonia was next examined for 
gallic acid. A strong solution of it was precipitated by glue, 
and the clear liquid evaporated to an extract and heated with 
spirits of wine. ‘The spirits of wine were distilled off, and the 
residue treated with zther exactly as sumach had been. A very 
small quantity of crystals was obtained. They exhibited the 
reactions of gallic acid on salts of iron and other reagents, 
and when distilled yielded crystals of pyrogallic acid. I have 
every reason to believe that these crystals were gallic acid, 
though from the smallness of their quantity I was unable to 
subject them to analysis. Valonia, therefore, may be regarded 
as containing a little gallic acid, but its quantity is so inconsi- 
derable as probably not to amount to a thirtieth of what su- 
mach contains. 
The most concentrated solutions of valonia give a very 
scanty precipitate when treated with sulphuric acid; and a 
large quantity of valonia must therefore be employed to yield 
any quantity of tannin by this process. ‘The precipitate has 
a bright yellow colour. When distilled it left a very bulky 
charcoal, and gave scarcely any empyreumatic products. The 
liquid which passed into the receiver was nearly colourless, 
and did not give the least indication of pyrogallic acid. The 
tannin of valonia appears, therefore, essentially different from 
that of nut-galls. 
Oak Bark.—The extract of oak bark when dried and di- 
stilled, also gave no indication of pyrogallic acid. I then en- 
deavoured to obtain gallic acid by treating a decoction of oak 
bark in the way already described. ‘Though I operated on 
