14 



BULLETIN 309, U. S. DEPARTMENT OF AGRICULTURE. 



Table I . — Fiber yields from two bone-dry cooks of zacaton grass, using different concen- 

 trations of caustic soda under a steam pressure of 90 pounds to the square inch. 





Quan- 

 tity. 



Caustic soda. 



Time 

 boiled. 



Pressure. 



Yield. 



Cook. 



Per 

 liter. 



Per- 

 cent- 

 age. 



Screen- 

 ings. 



Screened 

 fiber. 



Pith. 



Long 

 fiber. 



Total 

 fiber. 



No.l 



Grams. 

 404 

 400 



Grams. 

 19.7 

 29.0 



24.4 

 23.0 



Hours. 

 6 

 7J 



Pounds. 

 90 

 90 



Per ct. 



4.7 

 4.6 



Per ct. 

 35.4 

 37.1 



Per ct. 

 7.5 



Perct. 

 27.9 



Per ct. 

 40.1 



No. 2 



41.7 











Cook No. 3 was made in the rotary by treating 2,400 grams of 

 grass, bone-dry weight, with 19 per cent of caustic soda at a con- 

 centration of 71 grams per liter for 6 hours at a steam pressure of 

 80 pounds per square inch, which gave a yield of 50.8 per cent of 

 total fiber. The pulp was very uniform, soft, and of good appearance, 

 and the cooking conditions were not as harsh or expensive as those 

 for commercially treating poplar wood. 



Cook No. 4 was made from a bale of zacaton which was received in 

 a dry but very moldy condition, and the grass was quite brittle. 

 A charge of 2,400 grams was treated with 19 per cent of caustic soda 

 at a concentration of 70 grams per liter for 6 hours at a steam pressure 

 of 80 pounds per square inch, giving a yield of 49 per cent of total 

 fiber. It was impossible to distinguish any difference in quality 

 between the pulp from the sound and that from the moldy grass, the 

 fungi apparently attacking only the less resistant forms of hemi- 

 celluloses. 



Cook No. 5 was made by treating 2,000 grams of zacaton with 18 

 per cent of caustic soda at a concentration of 70 grams per liter for 

 5 hours at a steam pressure of 90 pounds per square inch, giving a 

 yield of 44.6 per cent of total fiber. 



Cook No. 6 was made by treating 2,400 grams of grass with 16 per 

 cent of caustic soda at a concentration of 70 grams per liter for 5 J 

 hours at a steam pressure of 90 pounds per square inch, giving a fiber 

 yield of 47.7 per cent of the total bone-dry grass. The expenditure 

 of soda and time was very moderate, the yield was very fair, and the 

 general appearance of the pulp was remarkably good. 



MICROMEASUREMENTS OF FIBER AND OTHER CELLS. 



Table II shows the comparative measurements of the cells of 

 zacaton grass. The measurements were made on the screened stock 

 from which paper No. 76 was made. 



Table II. — Comparison of the cell measurements of fibers and other cells of zacaton grass. 



Measurement. 



Parenchyma of pith . 



Long epidermal 

 cells. 



Parenchyma. 



Bast. 





Length. 



Width. 



Length. 



Width. 



Length. 



Width. 



Length. 



Width. 





Mm. 

 0.112 

 .072 

 .092 



Mm. 

 0.072 

 .057 

 .061 



Mm. 

 0.079 

 .072 

 .075 



Mm. 

 0.011 

 .011 

 .011 



Mm. 

 0.223 

 .162 

 .193 



Mm. 

 0.058 

 .018 

 .038 



Mm. 

 3.0 

 .5 

 1.7 



Mm. 

 0.013 





.005 





.0085 







