22 



BULLETIN 309, U. S. DEPARTMENT OF AGRICULTURE. 



Screened pulp from the four cooks was combined into one beater 

 charge, heated to about 40° C, and after being thoroughly mixed 

 with bleach liquor to the equivalent of 21 per cent of its bone-dry- 

 weight of commercial bleaching powder, was pumped to a bleach chest 

 to exhaust. When the bleach was practically all consumed and the 



Fig. 12. — Semicommercial rotary pulp boiler. 



color of the stock was found to be satisfactory, it was drained and 

 washed free from bleach residues. 



The bleached stock was then beaten with a medium brush for 2J 

 hours, loaded with 25 per cent of clay, sized with a 0.5 per cent resin 

 size and 2 per cent of alum, and run through a Jordan refiner and 

 then to a 30-inch Fourdrinier paper machine speeded to 90 feet per 

 minute. The stock acted very well on the paper machine, giving 



