50 FOREST PRODUCTS 



by a well-defined process, the water used in washing is reduced to a 

 minimum amount. All of this liquor is saved and is conveyed by pumps 

 and pipe lines to an evaporator where the soda is recovered. 



The next step in the process is bleaching the fibers, which is touched 

 on briefly elsewhere. All soda pulps intended for conversion into paper 

 must be bleached. 



The Recovery of Spent Liquors. 



The spent cooking liquor and the washings are pumped into an evap- 

 orator which is operated by a multiple effect vacuum apparatus where 

 the water is removed and it is reduced to a thick syrup. This concen- 

 trated liquor is then burned in special furnaces, this burning consuming 

 all of the organic matter and leaving a black mass which consists mainly 

 of carbonate of soda. The mass is then washed with water to remove 

 the carbonate which is later converted into caustic soda by being boiled 

 with lime. 



Collecting the Pulp. 



The remainder of this process is exactly like that of any other process 

 and will not be taken up in detail here as it has been described in the two 

 preceding processes. 



Reviewed briefly it consists of a very thorough screening of the pulp 

 to separate the fibers from the slivers and any other large, uncooked 

 pieces of wood or foreign material. The pulp is then screened from the 

 water and run out in the form of laps containing from 40 to 60 per cent 

 of water or run out in dry rolls which contain about 18 to 20 per cent of 

 water. 



Tests of this pulp for water content, strength, etc., are made and the 

 pulp is either shipped to the paper mills where it is made into paper or it is 

 made directly into paper at the mill where it is reduced from the wood. 



A great advantage in the reduction of wood by the soda process lies 

 in the fact that comparatively little care is necessary in preparing the 

 wood because of the great solvent power of the alkali. The process will 

 reduce small pieces of bark and even small knots as well as the chips. 



THE MANUFACTURE OF PAPER FROM WOOD PULP 



The manufacture of paper consists of the formation of a continuous 

 sheet or web made of minute structural units of pulp. The processes of 

 papermaking are of a mechanical and physical nature to a large extent 

 in contrast to the manufacture of wood pulp by the various chemical 



