46 
THE TANNIN, S’. 
after macerating for one hour, the strainer is pressed 
into the cylinder and the solution poured into a litre 
flask. The strainer is then drawn up, and, without re¬ 
moving it, 200 cc. of hot distilled water are poured in 
so as to wash the liquid and powder adhering to the 
strainer down into the vessel, which is immediately 
set in a water-bath and heated for one-half hour, the 
strainer pressed down, and the solution poured into 
the litre flask. This operation of hot extraction is 
continued until 1000 cc. of infusion are obtained; it 
is then allowed to cool, cold water is added to bring 
the solution again up to the mark, and the whole is 
filtered. The tannin strength of the solution should 
be such that 10 cc. will not reduce more than 8 cc. of 
permanganate solution. 
It is sometimes desirable to distinguish between the 
easily soluble tannin and the difficultly soluble tannin. 
That which dissolves in cold water is accepted as rep¬ 
resenting the former, while that which is afterwards re¬ 
moved by hot water represents the latter. The infusion 
of these may be prepared by extracting in the Von 
Schroder apparatus with cold water until one litre is 
obtained, and then preparing a litre of the hot infusion 
from the residual material. 
It was suggested by the Commission to employ a 
Heals press for the cold extraction of the tannin ma¬ 
terial. This consists of a closed cylindrical percolator 
of metal so arranged as to allow the water to be applied 
under the pressure of a column one and one-half metres 
in height. 
The accompanying illustration (Fig. 2) is of an ap¬ 
paratus which may be constructed in any laboratory, 
