Bart III.] Raitt : Bamboo as Material for Paper-pulp. 21 
better grades are concerned which entail bleaching to a white shade, for 
it is frequently the case that the brown soda or sulphate pulp is more 
easily bleachable than the pale yellow sulphite. This is especially the 
case with sulphite pulps made from resinous and dark coloured woods, 
hence it is chiefly confined to the treatment of Spruce which has little 
resin and possesses a good natural colour. When colour difficulties are 
present, it is not suitable unless a market exists for the pulp in its yellow 
unbleached condition. But bamboo pulp is so emphatically suitable 
for better uses that it would be misplacing it entirely to devote it to pur¬ 
poses for which an unbleached yellow cellulose is good enough, and the 
cost of bleaching bamboo sulphite pulp is so much greater than for bam¬ 
boo soda or sulphate pulps that any economy of sulphite over soda 
liquor is lost. 
25. There is also the question of its suitability to tropical conditions 
to be considered. Sulphur dioxide is a volatile gas and its successful 
absorption in water, or lime-water, is adversely affected by temperature, 
either of water or atmosphere, higher than those normal to northern 
latitudes. Even in Europe and North America much difficulty is ex¬ 
perienced during abnormal heat waves, and I am unable to see how this 
process could be successful where such high temperatures are normal 
during the greater part of the year, unless by the adoption of refrigera¬ 
tion, the cost of which would destroy any advantage of economy the 
process possesses. 
26. Notwithstanding the foregoing considerations it seemed desir¬ 
able not to overlook any special virtues it might possess for the treat¬ 
ment of bamboo. It was accordingly given a fair trial. As the liquor is 
corrosive of iron or copper the digestions were conducted in gas-tight 
earthenware jars fitted inside the digesters. It was found that bamboo 
is very sensitive to charring in liquors of a greater density than 7° Tw. 
or at temperatures above 150°, or in liquor containing an insufficient 
proportion of free sulphur dioxide ; but in a comparatively weak liquor 
of the following composition it digested perfectly in ten hours, of which 
4 were occupied in slowly raising the temperature to 145 , it being then 
maintained at that point for a further six hours i 
Per cent. 
Total S0 2 . 3 ‘60 
Combined S0 2 . 1-46 l Density 5° Tw, 
Free S0 2 .2-14 C 
Combined lime . • • • 1*28 ) 
[ 201 ] 
