22 



BULLETIN 309, U. S. DEPARTMENT OF AGKICULTUEE. 



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 2 J 

 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 machme speeded to 90 feet per 

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



