42 
THE TANNINS. 
unless a gelatinous tissue can be made that is com¬ 
pletely insoluble in water, the process is not available. 
Muntz and Ramspacher contrived an apparatus for 
use in Hammer’s method, which consisted of a press so 
constructed that the tannin solution could be forced 
through hide, the specific gravity taken before and 
after, or a portion of the liquid evaporated in each 
case. It, however, had no advantages over the original 
method, and has been used but little. 
4. Under the fourth class of methods we have prac¬ 
tically one in which the use of potassium permanganate 
is combined with the gelatin or hide method. The use 
of calcium hypochlorite has been suggested to replace 
the permanganate, but with no apparent advantage. 
Monier in 1858 first proposed the use of potas¬ 
sium permanganate for volumetrically determining the 
amount of tannin by adding the reagent until the 
solution assumed a pinkish color. It was soon found, 
however, that tannin was not the only substance oxi¬ 
dized by permanganate, and in infusions the color 
interfered with the determination of the end reaction. 
In 1860, Lowenthal rendered the process more avail¬ 
able by suggesting the use of indigo as an indicator, 
which at the same time controlled the oxidation, and 
this he further greatly improved in 1877 by combining 
the gelatin process with it, making a permanganate 
valuation, before and after treatment with gelatin. 
Neubauer in 1871 suggested a similar improvement, 
using animal charcoal instead of gelatin. 
The permanganate method, with further improve¬ 
ments by Procter, Hunt, Yon Schroder, Councler, and 
others, has come to be regarded as the standard process 
