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459 
All four of the pulps were light-gray in color and they appeared to be 
well reduced. ‘The digestions were carried out in an autoclave built of 
bronze and the heating was done with direct fire. By the use of patent 
boilers of the vomiting type and by heating with direct steam (improve- 
ments which are in general use with esparto grass) results equal to 
those given above could no doubt be brought about in a much shorter 
time. The pulp has a great tendency to form little balls which are very 
similar to those encountered with esparto and straw, hence rotary boilers 
would not be suitable. ‘The modern tendency is either to increase the 
pressure or the amount of caustic soda used, thus diminishing the dura- 
tion of the digestion. 
Two digestions with 2 per cent liquor, but with 20 per cent caustie soda, 
calculated on the weight of the material, were carried out at 4 to 5 atmospheres 
pressure for three hours. The yields of pulp were 44 and 45 per cent, respec- 
tively. 
In some cases, esparto and straw are boiled in open kettles, but if this 
is done, a much longer time is required to accomplish the same result. 
The following table gives the results of two such experiments: 
Digestion of cogon at ordinary pressures. 
dq ie 
Strength of liquor (per cent) 2.6 o 
Caustic soda (per cent) 13 15 
Time of boiling (hours) 12 12 
Yield of pulp (per cent) 51. 25 48. 81 
These results show that cogon could be boiled in open digesters with 
good results, to make the cheaper grades of printing paper, where time 
is not as important a factor as the cost of the process. The use of quick- 
lime, the chemical so commonly employed in the manufacture of straw- 
board, did not give satisfactory results with cogon grass because the lime 
seems to combine with the soluble constituents from the grass and_ it 
then becomes extremely difficult to wash out. The pulps produced in 
this manner in the laboratory were coarse and brown. However, for the 
cheapest printing paper and for boards, a lime boiling in.an open cook, 
or perhaps under 1 to 3 atmospheres pressure, would effect great saving 
in the cost of the chemicals to be used. 
The investigation of cogon also proved that no preliminary cutting 
down of the grass is necessary; after being dried and hand picked or 
machine cleaned it is fit for immediate digestion. 
THE BLEACHING OF COGON GRASS PULP. 
Raperiment No, 1.—The residue from digestion No. 3, page 458, amounting to 
454.2 grams, was repulped in 10 liters of water; 1 liter of a bleaching solution 
of 2.35 per cent available chlorine (approximately 10° Bé.) was added and the 
