TANNINS FROM WATTLE BARK. 
barks do not account for all the tannin in the original bark—a small percentage, 
apparently, experiences some chemical change. * The tannin may itself change, or 
it may combine with some material in the bark. 
PROCESS. : 
First Day—The process was started by filling all the vats with bark, and 
then the bark in A was filled with 4,150 ¢.c. of water at 9 a.m. 
Second Day—At 9 a.m. the liquor was drawn off from A (at the bottom) 
as far as possible, and amounted to 2,600 c.c. This good tanning liquor was not 
returned to any of the vats. Immediately after taking off this liquor, 2,600 c.c. 
of water were added to vat A. At 1.30 p.m. another 1,550 c.c. were added to 
vat A, and this resulted in about 1,500 c.c.-of liquid overflowing into B, which 
had been previously filled with bark. At 5 p.m. another 2,600 c.c. of water 
were added to A; this resulted in an overflow to B, which by this act was 
filled completely. 
Third Day.—At 9 a.m. 2,600 c.c. of liquor were drawn off from B, and 6,750 c.c. 
of water were added to A, as described for the second day. At 5 p.m. sufficient 
water had been added to A to press forward the volume of liquor required to 
cover the bark in C. c ; 
Fourth Day.—2,600 c.c. of liquor were drawn off C, 6,750 c.c. of water were 
added to A, and the bark in D was thus covered with liquor. 
Fifth Day.—2,600 e.c. of liquor were drawn off D, 6,750 ¢.c. were added to A, 
and the bark in E was thus covered with liquor. 
Sixth Day.—2,600 c.c. of liquor were drawn off E, 6,750 ¢.c. were added ‘to A, 
and the bark in F was thus covered with liquor. All the vats in the battery 
were now filled with bark and liquor. F was at the head and A was at the 
tail-end of the battery. ; 
Seventh Day.—2,600 c.c. of liquor were drawn off F. All the weak liquor, 
approximately 2,600 ¢.c., was run off A (which now contained spent bark), and 
put on to the bark in B. The spent bark was removed from A, and A then 
received a-fresh lot of dry bark. B received 1,550 c.c. of water at 1.30 p.m. 
and 2,600 c.c. at 5 p.m. A was now at the head and B was at the ail-end of 
the battery. 3 
The process was continued on the same lines as laid down for the seventh 
day. Hach vat only occupied the position at the head of the battery for one 
day. The 2,600 ¢.c. of liquor drawn off at the head of the battery at 9 a.m. 
each day was analyzed and the results shown for each experiment. The liquor 
from the spent bark replaced by gravitation the liquor removed at 9 a.m, from 
the head of the battery, and then a volume of water was used per day equal 
to that volume of liquor required to cover the daily quota of dry bark. This 
water was added in two portions—one at 1.30 p.m. and the other at 5 p.m. 
Loss by evaporation, slight differences in the size of the vats, and variations in 
the volume of liquid removed with the spent barks were responsible for slight 
changes in the volume of water used per day. z 
When the liquor for analysis was drawn off the last bark in each experiment 
there was still a considerable amount of tannin remaining in the battery, all 
the vats being filled with partially spent bark. No alteration was made in the 
volume of water used per day, and the resulting overflow liquors were collected 
and analyzed after they had passed through the last bark. These results are of 
special value, because they show the tannin and barkometer strengths of every 
liquor that passes through the last bark for each experiment. In some experi- 
ments these liquors were carried forward to the next one, and the total tannin 
is deducted. i 
With reference to the foregoing process, it will be noticed that— 
(1) the total voliime of liquor that passes through any one vat is pro- 
portional to the number of vats; ; 
(2) the time covering the period that the bark remains in the vat is 
proportional to the number of vats; 
(3) when the full time for the “one liquor period” is rigidly adhered 
to, the water required for the complete extraction of a given weight 
_ of bark will be at its minimum; : 
(4) as the volume of water used for the extraction of a given weight of 
bark increases, the number of vats required for the battery decreases. 
153 
