22 
BULLETIN 404, U. S. DEPARTMENT OF AGRICULTURE. 
4-foot logs are chipped by a heavy, comparatively expensive chipper 
of high power consumption, after which the chips are sorted by 
sieving, the large pieces being rechipped. There would be a note- 
worthy difference in the installation, operating, and depreciation 
costs of the two equipments, and this difference would counterbal- 
ance to a considerable extent the difference in cost of raw material 
storage. 
It is possible that in the use of the chip loft more care would have 
to be exercised in using hurds because of the tendency of the bast 
fiber to cause lodgments, but this should not be considered a serious 
difficulty. 
The weight of hurds which are capable of being charged into a 
rotary is a decidedly unfavorable factor. The weight of a cubic 
foot of hurds varies somewhat with the proportion of bast fiber, 
but averages about 5.4 pounds, which, compared with a cubic foot 
of poplar chips at 8.93 pounds, represents a digester charge of 60.5 
per cent of the weight of a poplar-wood charge, or, in terms of fiber 
capacity, the hurds charge would yield 38.6 per cent as much fiber 
as the wood charge. The hurds upon being baled for transporta- 
tion may be broken and crushed to such a degree that the weight 
of the charge may be increased, and it might be found possible to 
increase the charge weight by steaming or by the employment of 
tamping devices. This small weight of charge constitutes one of the 
most serious objections to the use of hurds in paper manufacture. 
In those tests in which the most satisfactory results were obtained, 
the cooking conditions were 29.5 per cent of caustic soda at a concen- 
tration of 107 grams per liter and a causticity of 84.0 per cent acting 
at a temperature of 170° C. for five hours, or a total time of seven 
hours. The steam condensation in the rotary used for these tests 
was abnormally high, due to the fact that the steam supply pipe was 
uncovered for a considerable distance and the rotary was entirely 
uncovered. It is believed, therefore, that a larger amount of caustic 
was necessary than would otherwise have been the case. This 
belief is strengthened by the quality of the waste liquor from one of 
the later cooks, which gave on analysis 16.85 grams per liter of free 
caustic soda and showed a causticity of 27.75 per cent. These data 
show that only 67.3 per cent of the total caustic employed was actu- 
ally consumed in the cooking operation, which percentage is lower 
than obtains in practice. The stock from this cook was bleached 
with 11.5 per cent of bleach. But even as the figures stand, the 
comparison with poplar cooking practice is as follows: 29.5 per cent 
caustic soda used as against 22 to 25 per cent; 107 grams per liter 
as against 100 to 110; 84 per cent causticity is little different than 
obtains in practice; 170° C. is about commercial practice; five hours 
at pressure as against four to six hours; seven hours' total time as 
