ZACATON AS A PAPEE-MAKING MATEKIAL. 



23 



Tery little trouble and producing a machine-finished sheet of good 

 -appearance and quality. Physical tests on this sheet, designated as 

 No. 41, are recorded in Table VIII. 



Since the installation of a rotary type of digester by this bureau, 

 further tests were made on Epicampes under the more favorable 

 conditions afforded by this method of treatment. The rotary 

 measured 6 feet in length by 4 feet in diameter, and was supplied 

 with a large man head, thermometer well, pressure gauge, steam 

 inlet, and steam relief through the hoUow trunnions, and rotated at 

 one-half a revolution per minute (fig. 12). A charge of 350 pounds 

 €Ould be handled conveniently, using a much stronger caustic solu- 

 tion and yielding a more uniform pulp. 



The cooked charge was dumped into an iron drain tank under- 

 neath, where, by means of a false bottom, the fiber could be drained 

 and washed with no loss. By means of a vacuum under the false 

 hottom, the water could be drained from the fiber uniformly, leaving 

 only 70 to 80 per cent of water in the fiber, in which condition it 

 could be sampled and weighed with a good degree of accuracy. 

 Uniformity of chemical action on the grass was very noticeable and 

 assisted very much in the subsequent operations and quality of the 

 pulp. 



The grass used for these tests was of good, medium quahty and in 

 perfect condition. Four cooks were made, in order to secure suffi- 

 cient pulp for a fair trial on the beating engine and paper macliine, 

 the cooking conditions of which are shown in Table VI. 



Table VI. — Conditions of trials of four cooks of zacaton pulp. 



Cook. 



No. 11 



No. 12 



No. 13 

 No. 14 





Grass. 





Air 

 dry. 



Bone dry. 



Per 

 cent. 



Pounds. 



Pounds. 

 341 



361 



335 

 342 



90.7 



91.0 



90.8 

 90.8 



309 



328 



304 

 311 



Rela- 

 tion of 

 caustic 



soda 

 added. 



Per ct. 

 19.0 



20.1 



20.2 

 20.3 



Strength 

 of caustic 

 solution. 



Per cent. 

 9.18 



9.18 



9.18 

 9.18 



Caustic 



soda 



added. 



Pounds. 



58.9 



66.0 



61.6 

 63.2 



Caustic 

 solu- 

 tion 



added. 



Gallons. 



77 



86 



81 

 82 



Maximum temperature, 

 boUing. 



Time 



to 

 reach. 



Hours. 



Heat 

 used. 



C. 



160 



166 



160 



166 



166 



166 



Time 

 held. 



Hours. 

 6 



As seen by the table, the cooking was controlled by temperature 

 instead of by steam pressure. Since it is temperature and not 

 pressure which induces chemical action, and since steam pressure is 

 indirectly an expression of temperature, it is obviously correct to 

 employ either for control. On account of the presence of more or 

 less air in the steam supply, and on account of gases which are 



