BULLETIN 80, U. S. DEPARTMENT OF AGRICULTURE. 



If any one of these conditions be altered and the other two kept constant, the yield 

 varies inversely as the altered condition. Thus, in the case of esparto, the author 

 performed a series of experiments in which the proportion of caustic to unit weight of 

 esparto was varied, whilst the temperature and duration of time of digesting were both 

 kept constant with the following results (Table 2). 



Table 2. — Experiments regarding yield of air-dry bleached palp from Oran esparto. 



No. of ex- 

 periment. 



Esparto, 

 weight 

 taken. 



Soda liquor. 



Conditions of boiling. 



Weight of 

 air-drv 

 pulp: 



Dry pulp 

 on dry" 

 esparto. 



Bleaching 

 powder. 



Volume. 



Na 2 0. 



Time. 



Tempera- 

 ture. 



Pressure. 



1 



Grams. 

 200 

 200 

 200 



Cc. . 

 800 

 800 

 800 



Per cent. 

 1.58 

 2.13 



2.69 



Hours. 

 3 

 3 

 3 



"C. 



142 

 142 

 142 



Lbs. 



55 

 55 

 55 



Grams. 

 87.30 

 80.67 

 72.00 



Per cent. 

 43.91 

 40.55 

 36.20 



Per cent. 

 29.5 



2 



18.5 



3 



10.5 











Variable. 

 Pressure varied. 

 Strength of caustic varied. 

 Time varied. 



Note. — The different trials were made in wrought-iron tubes fitted with screw caps, all three being 

 heated together in an oil bath for three hours at a temperature of 302° F. (55 pounds above atmosphere). 



The following is taken direct from Cross, Bevan, and Sindall's 1 

 resume of Beveridge's experimental results, which include the data 

 quoted in Table 2 and others: 



He made three sets of trials, as follows: 

 Constant conditions. 



1. Time and strength of caustic. 



2. Pressure and time. 



3. Pressure and strength of caustic. 

 The results were: 



1. Increase of pressure resulted in a diminution of yield, the quantity of pulp 

 obtained being reduced considerably. 



2. Excess of caustic soda caused rapid diminution in the yield of cellulose. 



3. Gradual exhaustion of the caustic soda by prolonged digestion prevented such 

 serious diminution of yield. 



The discussions and experimental results which have been quoted 

 show in a general way the effects of varying some of the fundamental 

 cooking conditions in the soda process. None of the experiments 

 cited are directly comparable to commercial practice in this country, 

 because the testing conditions were not sufficiently representative of 

 manufacturing conditions, and, in the case of Beveridge's experi- 

 ments, because esparto — a grass, or pectocellulose — was used as the 

 test material. Moreover, the effects of the cooking conditions 

 employed were not studied in as great detail as seemed desirable. 

 The experiments show very clearly, however, that improper cooking 

 conditions are wasteful or inefficient, and indicate the need for com- 

 plete experimental data on which improvements in commercial 

 practice may be based. 



i Wood Pulp and Its Usea, p. 132, 1911. 



