22 BULLETIN- 404, U. S. DEPARTMENT OP 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 

 imcovered. 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 com.mercial practice; five hours 

 at pressure as against four to six hours; seven hours' total time as 



