Part III.] Raitt : Bamboo as Material for Paper-pulp. 
25 
them more completely and permanently in solution so that they can be 
more thoroughly washed out of the pulp. The colour of the unbleached 
product can thus be considerably improved and the subsequent con¬ 
sumption of B. P. reduced. But NaOH in excess of that required for the 
resolution of the non-cellulose has, at the temperatures employed, a seri¬ 
ously destructive effect on the fibre, so its use for this purpose is limited 
by the extent to which it is profitable to sacrifice yield in order to gain 
colour. It becomes a matter of balancing the costs of raw material, 
NaOH and B. P. against the ultimate yield of bleached pulp. To a fac¬ 
tory in India these may be taken, for our present purpose, to be Rs. 15, 
Rs. 75 (with aid of recovery plant) and Rs. 125 per ton respectively. 
Slight differences in fuel cost for the variations in temperature and time 
employed may be neglected as too small to appreciably affect the nett 
results. If these items be reduced to units and divided by the bleached 
yield, we obtain a series of unit cost figures giving us a relative and 
comparative view of the economic results. Taking bamboo (B) as 1, 
NaOH ( n) will be 5 and B. P. ( b) 833, final bleached yield being represent¬ 
ed as ( y ). 
. (B xl) + (nx5) + (6x8-33) Un . tco ^ 
y 
The following gives the average results of experiments made to deter¬ 
mine how far excess NaOH may be profitably employed to reduce colour ; 
time and temperature being in each case 177° for 1 hour and 162° for 4 
hours :— 
No. I. 16 per cent. NaOH, unbleached yield 49 per cent., required 36 per cent. 
B. P. (17-6 on raw material), bleached yield 43-2. 
No. II. 18 per cent. NaOH, unbleached yield 47 per cent., required 29 per cent. 
B. P. (13*6 on raw material), bleached yield 43*0. 
No. III. 20 per cent. NaOH, unbleached yield 44 per cent., required 23 per cent. 
B. P. (10*1 on raw material), bleached yield 41*5. 
No. IV. 22 per cent. NaOH, unbleached yield 41 per cent., required 20 per cent. 
B. P. (8*2 on raw material), bleached yield 39-0. 
Unit cost being :— 
No. I. (100xl) + (l6x5) + (17-6x8-33) 
43-2 
No. II. (100X 1) +(18x5)+ (13-6x8-33) 
43 
No. III. (100x1) + (20x5) + (10-1x8-63) 
41-5 
No. IV. (100x1)+ (22x5)+(8-2x8-33) 
39 
[ 205 ] 
= * 7-56 
= 7-05 
= 6-84 
7-14 
