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Indian Forest Records . 
[Vol. Ill 
a material requiring methods of treatment suitable to its peculiarities 
and one to which our experience of other cellulose producers has but 
limited application, and is one of the chief causes of the high and 
variable bleach cost figures which have been reported. 
20. The pectose is readily soluble in boiling NaOH solutions, but 
gelatinises at the higher temperatures employed in digestion and is, 
therefore, liable to become mechanically bound to the cellulose and 
difficult to wash out in the case of material treated in chip form. When 
this occurs the difficulty of the subsequent bleaching is considerably 
increased. The smaller the particle the less will this mechanical binding 
occur in the interior,—hence the advantage of crushed material is very 
marked upon this point. With pectose, fat and wax may conveniently 
be grouped as the latter is insignificant in amount and is soluble under 
similar conditions. Together they neutralise or abstract from the 
digestion liquor *32 per cent, of NaOH on the raw material for each 
1 per cent, found on analysis. 
21. Unlike pectose, lignin is not soluble in w r eak solutions nor at 
temperatures below 130°, and with strong solutions and high tempera¬ 
tures the danger of serious hydrolysis and destruction of fibre comes into 
play. The weaker the solution and the lower the temperature, the higher 
the cellulose yield, but the minimum limit with both is the point at which 
lignin is no longer soluble. Its resolution is essentially a process of saponi¬ 
fication and it must be borne in mind that it has to be transformed into 
a soap which remains soluble in the cold, otherwise precipitation on the 
pulp would occur during the subsequent washing. Crushed material, 
by its large bulk, entails the use of a large volume of comparatively weak 
liquor, and this, to a considerable extent, eliminates the hydrolysing ten¬ 
dency of strong liquor. In general, the digestion liquor will not exceed 
12° Tw. In liquors of this strength, the lowest temperature at which the 
permanently soluble saponification of the lignin can be effected is 150° 
and the consumption of NaOH is equal to -66 per cent, on the raw 
material for each 1 per cent, found on analysis. The duration of diges¬ 
tion required is 3 hours. The experiments to arrive at these results 
were carried out on material scraped to extremely fine and thin shavings 
in order to reduce penetration resistance to a minimum and from which 
water solubles, fat and wax, and pectose w r ere previously extracted, and 
they give us the absolutely irreducible minima of conditions necessary 
for digestion under nearly perfect resistance conditions, viz., a tempe¬ 
rature of 150° for three hours using liquor of 12° Tw. The problem of 
how far it is necessary to raise these conditions in order to overcome 
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