GROUND- WOOD PULP. 11 



of white water used and determining the wood fiber in a sample of it. 

 This proved rather unsatisfactory, and was discontinued on account 

 of the difficulty in removing the wood fiber from the white water 

 sample. 



The yield of pulp has been calculated to a basis of 100 cubic feet of 

 solid rossed wood, this factor being thought more satisfactory and 

 accurate than a measured cord, and representing approximately the 

 solid content of a piled cord of 2-foot rossed wood containing 128 

 cubic feet. 



TESTS ON THE PAPER. 



The sample of pulp to be run into paper was first shredded and the 

 moisture determined. The required amount was then weighed out 

 and mixed and beaten with a weighed amount of bleached spruce 

 slow-cook sulphite. In some runs, particularly those made on some 

 of the pulps made from cooked woods, the sulphite was dispensed 

 with. The mixture, usually 20 per cent sulphite to 80 per cent 

 ground wood, was beaten until the fibers were separated, generally 

 about 1 hour. The stock was then run out on the paper machine 

 and an uncalendered sample was taken for strength and color tests. 



No size, color, or loading was added to any of the sheets, the desire 

 being to present the pulps made from different woods and under 

 different conditions in as nearly comparable conditions as possible. 



The uncalendered samples of paper were tested for tensile strength, 

 lengthwise and crosswise, by means of a Schopper breaking length 

 tester, and for bursting strength by means of a Mullen tester. The 

 color tests were made with an Ives tintphotometer and measure- 

 ments were made of the thickness of the sheet and weight per ream. 



EFFECT OF PRELIMINARY TREATMENT OF SPRUCE. 



Spruce has been used for many years as a raw material for ground- 

 wood pulp, but the effect of the production of pulp from it under 

 varying conditions has never been given very careful study. Depend- 

 ing on the quality of the product desired, different conditions of 

 grinding must be selected, and in some cases the wood must even be 

 given a cooking treatment prior to grinding. In the manufacture of 

 container board, where great strength is desired and the color is of 

 lesser consequence, strength is often increased by the addition of 

 sulphite or sulphate pulp, screenings, or old paper stock. In the 

 manufacture of news print paper, strength is desired too, but not 

 nearly so much strength, the color, yield, and finishing characteristics 

 here being the prime consideration. The work which has been done 

 on spruce has been carried on with the idea of attempting to increase 

 the efficiency of grinding both from the standpoint of reducing the 

 power consumption and increasing the yield from a cord of the raw 

 material in either the cooking or ordinary ground-wood process, and 



