FOREST SERVICE, 547 



ture of grinding, and the physical condition of the wood upon the 

 resultant factors of the horsepower which must be applied to the 

 grinder, the amount of pulp produced in 24 hours, the horsepower 

 consumption per ton of pulp, and the yield and quality of the pulp. 

 The results should be of great value to the industry in establishing 

 standards of practice, increasing the efficiency of grinding, and 

 reducing the cost of operation. 



The eliect of steaming or boiling wood previous to grinding was 

 determined in part during the year. It was found that such treat- 

 ment produces a pulp of greatly increased strength, though of a 

 darker color. It is possible that woods not suitable for grinding in 

 their natural state may be rendered suitable by some preliminary 

 treatment, and that the ground wood pulp thus obtained can be used 

 for tough wrapping papers which now require chemical pulps. 



In the tests to determine the relative suitability of various species 

 for the production of soda and sulphite pulps, redwood, redwood 

 bark, red fir {Abies magniflca), lodgepole pine, and sand pine were 

 studied. In addition, a small quanity of mill waste from Mexico 

 (consisting mostly of Pinus ponderosa) was tested at the request of 

 the State Department. The yields from the best cooks of these 

 materials ranged, in the soda process, from 34.9 per cent for redwood 

 bark to 51.7 for the mill waste, and in the sulphite process from 33 

 per cent for redwood bark to 47.8 per cent for sand pme. 



The general etfect of the work with soda and sulphite pulps from 

 the various woods is seen in the increasing use by pulp mills of species 

 which a few years ago were not thought suitable for the commercial 

 manufacture of paper pulp. 



There is reason to believe that the efficiency of commercial practice, 

 as well as of experimental work by the service, may be increased by 

 a knowledge of the relation of the fundamental cooking conditions 

 in pulp manufacture. The effects of the variable cooking condi- 

 tions — proportion of caustic soda to weight of wood, causticity of 

 cooking liquor, and temperature and duration of cooking — in the pro- 

 duction of soda pulp have been studied, and the relation of these 

 factors to the yield of crude and screened pulps, the consumption of 

 chemicals, and the quality of the resultant pulps determined. Simi- 

 lar experiments have been begim with the sulphite and sulphate proc- 

 esses, using several species of wood. 



WOOD UTILIZATION. 



Douglas fir, proba})ly the most important timber tree of tlie North- 

 west, has often been a prey to forest fires, which have left inmiense 

 quantities of dead standing timber. A study of such timber, made to 

 determine its rate of deterioration, usability, and strength, was com- 

 pleted during the year. It showed that fire-killed trees under 3 feet 

 in diameter usually remain merchantable for 8 or 10 years, while 

 larger trees with thin sajiwood may remain merchantable for 15 or 20 

 years. The strength of the dead timber was found to l)e but slightly 

 l^elow that of green material, thus indicating that the sound wood 

 from fire-killed trees may safely be used for general construction 

 purposes, 



A study of the production and consumption of the paper products 

 in the Pacific Northwest was coini:)leted. The results should prove 



