408 
Groom.— Brown Oak 9 and its Origin . 
Results. 
25 c.c. indigo solution required 
c.c. KMnO, 
43 * 9 ) 44.0 
44 -i P* 
„ +5 c.c. extract ordinary oak 67-5 c.c. „ 
„ + „ » brown „ 61-7 „ 
„ +20 c.c. pure tannin solution 61-5 „ „ 
The pure tannin solution was made by dissolving o-iii 8 grm. of pure 
tannin in water and making up to 25° c - c - 
20 c.c. pure tannin solution —> 6 1-5 — 44-0 = 17-5 c.c. KMn 0 4 
rrix/r ^ 20 *11 l8 
i.e. i c.c. KMnCL —» -x-grm. tannin. 
4 J 7-5 250 
= 0-00051 grm. tannin. 
5 c.c. ordinary oak extract —> 67.5 —44 = 23.5 c.c. KMn 0 4 
23-5 c.c. KMn 0 4 —> 23-5 x 0-00051 grm. tannin. 
.-. 500 c.c. „ ,, 23-5 X 100 x 0-00051 grm. tannin, 
and this is contained in 9 grm. of wood. 
n/ . 22-^ X IOO X 0-000*1 
.*. % tannin = -— x 100 
9 
= I 3*33* 
5 c.c. brown oak extract —> 61-7—44 = 17.7 c.c. KMn 0 4 
17-7 c.c. KMn 0 4 —> 17-7 x 0-00051 grm. tannin. 
.*. 500 c.c. contain 100 x 17-7 x 0-00051 grm. tannin, and this is con¬ 
tained in 9 grm. wood. 
n/ . 17-7x100x0-000^1 
.*. % tannin = - ! — L -— x 100 
= 10-05. 
