SUITABILITY OF LONGLEAF PINE FOR PAPER PULP. 17 
In the first series of tests, with an increase in the amount of sodium 
sulphide from 7.5 to 50 pounds per 100 pounds of wood, the yield 
decreased from 52 to 40.3 per cent. For amounts of 25 pounds 
or less the pulps were of good quality, being strong with good wearing 
properties, but for larger amounts the pulps became soft and fuzzy 
and evidently were overcooked. 
In the second series, increasing the amount of sodium sulphide 
from 1 to 5 pounds per 100 pounds of wood resulted in a decrease 
in the yields from 68.9 to 60.1 per cent. The largest amount (5 
pounds) afforded the best pulp, considering strength and wearing 
properties; the other pulps were much undercooked and quite 
brittle. 
The third series of tests, using a larger amount of caustic soda 
(20 pounds), showed the effect of increasing the amount of sodium 
sulphide from 2.1 to 8 pounds per 100 pounds of wood. Under these 
conditions, the yield was decreased from 64.3 to 47.7 per cent. 
The pulp obtained when using 2.1 pounds of sodium sulphide was 
slightly undercooked and somewhat brittle. The other pulps had 
fair strength and wearing properties and could be used for making 
a medium grade of wrapping paper. 
As the amount of sodium sulphide was increased, the disagreeable 
odor arising from the cooking was more noticeable, being much more 
offensive for cook 37 (50 pounds Na 2 S per 100 pounds of wood) than 
for cook 31 (7.5 pounds Na 2 S). Increasing the amount of sodium 
sulphide resulted in lighter-colored pulps, that from cook 37 being 
considerably lighter in color than from cook 31. 
Sodium sulphide is not so severe in its action on wood as caustic 
soda. A cook of 8 hours' duration was made with sodium sulphide 
only, using 40 pounds per 100 pounds of wood and a maximum cook- 
ing pressure of 100 pounds per square inch. A yield of 41 per cent 
was obtained, while a similar cook using caustic soda alone in the 
proportion of 20 pounds per 100 pounds of wood had a yield of 44.3 
per cent. This indicates that caustic soda is almost twice as effective 
as sodium sulphide in reducing the wood to pulp. The color of the 
pulp produced when using caustic soda alone was lighter than when 
using sodium sulphide alone. 
EFFECTS OF SODIUM CARBONATE. 
Sodium carbonate occurs in the commercial sulphate liquors due to 
incomplete causticization. That it is of no assistance in reducing 
longleaf pine was shown by a cook made with 40 pounds of this 
chemical, 10 pounds of caustic soda, and 5 pounds of sodium sulphide 
per 100 pounds of wood. The duration of cooking was 7 hours and 
