28 



BULLETIN 



U. S. DEPARTMENT OF AGRICULTURE. 



of consumption and subsequently decrease of percentage efficiency 

 are indicated. While the possibility of error is not ehniinated, 1 this 

 result indicates the need for further investigation. 



RELATION" BETWEEN" CAUSTIC SODA CONSUMED AND YIELDS. 



For the purpose of further studying the cooking effects of the 

 various conditions employed, yields of total crude pulps from all of 

 the cooks were platted against amounts of caustic soda consumed 

 per 100 pounds of wood charged (fig. 14). The average curve drawn 

 through these points indicates a definite relation between yields and 



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TEST VARYING 



©CONCENTRATION OF CAUSTIC SODA 

 OAM0UNT OF CAUSTIC SODA 

 ODURATI0N OF COOKING 

 ^PRESSURE OF COOKING 

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10 12 14 16 18 20 22 24 26 28 30 32 34 

 NaOH CONSUMED PER 100 PDS.0F BONE DRY W00D-PDS. 



Tig. 14.— Relation between yields and amount of caustic soda consumed. 



amounts of caustic soda consumed, regardless of the cooking condi- 

 tions. However, even if it is assumed that the location of some of the 

 points is due to experimental errors, the relation, as regards individual 

 cooks, can be only an approximate one, since it has already been 

 pointed out that in some of the tests increased cooking effects were 

 obtained without any increase in the consumption of caustic soda. 

 If the curve were produced for lower amounts of caustic soda, the 

 yields would probably be somewhere between 80 and 100 per cent 

 at zero consumption, since under these conditions cooking could still 

 be effected by water alone. 2 



I The test data show a loss of digester liquor overflowing through the "top relief" for cooks 25 and 26 

 (that for cook 26 showing the greatest loss), and it is due to the platted points for these two cooks that the 

 curves indicate greater consumption of caustic soda at the lower concentrations. 



5 See Tauss's experiments, Table 1. 



