DETECTION AND ESTIMATION OF TANNINS. 43 
of the present time, although it is not without its faults, 
and is especially difficult for one who only occasionally 
desires to make a tannin assay. 
In 1883 a Commission of German technical chemists 
was appointed to meet in Berlin and report on a 
method of tannin assay. This Commission consisted 
of Dr. C. Councler, Dr. J. v. Schroder, and Messrs. 
A. Eberz, Franz Kathreiner, Schaun, and F. Simand. 
W. Eitner, of Vienna, was prevented from taking part 
in the proceedings. In two years they presented a 
report, under the title of “Bericht liber die Verhand- 
lungeu der Commission zur Feststellung einer einheit- 
lichen Methodeder Gerbstoffbestimmung, Cassel, 1885. 
Verlag von Theodor Fischer.” In addition to the 
recommendations, this report contains a critical investi¬ 
gation of the Lowenthal method by Dr. von Schroder. 
The following process will give that recommended 
by the Commission, together with some improvements 
that have been suggested by various investigators since. 
Although far from perfect, it may be said to represent 
fairly the method of to-day, and is capable of giving 
satisfactory results in competent hands. 
Briefly outlined, the process, which is still known as 
Lowenthal’s, consists in taking a dilute solution of po¬ 
tassium permanganate, determining the amount of it 
necessary to decolorize or change to yellow a given 
amount of indigo solution, and then the amount re¬ 
quired to change the same volume of indigo solution 
and pure tannin solution. Another portion of the tan¬ 
nin solution is then treated with gelatin or hide pow¬ 
der, filtered, and portions of the filtrate and indigo 
which represent the same amounts as were previously 
