TANNINS FROM WATTLE BARK. 
The percentage (64.1) of total tannin extracted from the bark in the first 
experiment was low. If the process was efficient the amount of tannin that 
could still be removed at ordinary temperature would be reduced to a minimum. 
This was tested by taking one lot of spent bark as it came from the battery 
and placing it in a separate vat with suflicient water to cover it. After twenty- 
four hours the density of the liquor reached 2° barkometer, and at the end of 
fourteen days it was 3° barkometer. The percentage of tannins in this -liquor 
is low, but it could not be considered a negligible quantity. Spent bark from 
each experiment was tested at the temperature of the tail-end vat, from which 
the bark was taken. - c 
In the second experiment (No. 2) the temperature of the tail-end vats was 
raised to 95° during the work-day. At first only the sixth vat was brought up 
to the high temperature, but this produced a strong liquor, which could not be 
sufficiently reduced by the water and liquor passing from it in one day. The 
fifth vat was then heated also. The results obtained from the second experiment 
show a considerable improyement on the first. z 
The third experiment (No. 3) was a duplication of the last part of the 
second. Two tail-end vats were worked at a temperature of 95° from 8 a.m. 
to 5 p.m. each day. This represents the working day. No liquor or water was 
passed forward during the night, when the temperature was allowed to fall to 
a figure which varies according to atmospheric conditions. The results obtained 
from this experiment were considered to be good; and a fourth experiment 
(No. 4) was considered necessary to confirm them. 
The three next experiments (Nos. 5 to 7) only differed from the fourth as 
regards their temperature for the tail-end vats. These were kept at 80°, 60°, 
and 40° C. respectively. 
For the last experiment (No. 8) all the vats were maintained at a tem- 
perature of 35° C. for the whole of the time required to complete the experiment. 
In experiments Nos, 2 to 7 the hot liquors passing from the tail-end vats 
were responsible for an increase in the temperature of the fourth vat. The first 
three vats were allowed to remain at ordinary temperature for all excepting 
the eighth experiment. ; 
Ground Adelaide bark was used for all the experiments. It is extremely 
difficult to obtain samples of wattle-bark containing the same proportions of 
coarse and. fine particles. For this experiment the bark was passed through a 
sieve (twelve wires to the inch), and the proportions found for coarse and fine. 
Samples were taken from each and analyzed. The difference in tannin content 
between the fine and coarser particles did not amount to 1 per cent. of tannin 
on the weight of the bark. The daily quota of bark added to the battery . 
consisted of 1 Ib. of fine and 2 lbs. of the coarser particles. After careful 
sampling, a number of samples were made up, containing 3 lbs. of bark. At 
a later stage more samples were required, and the slight difference in the tannin 
values is due to the bark absorbing more moisture. : 
The following are the results obtained by analyses from two samples taken 
from bark used for the first three experiments* :— 
Analysis of Bark used for Experiments Nos. 1 to 3. 
Particulars. per cent, 
Tannin 37.55 
Non-tannins .. 10.68 
Insolubles i, a bar Bi 40.17 
Water ~ Per — its i as im 11.60 
Total a a Fat oe .. 100.00 
Note.—The numbers of the experiments in parentheses correspond to the 
numbers on the diagram on page 154. 
* For footnote see next page. Sy te 
155 YS 
