42 
BULLETIN 983, U. S. DEPARTMENT OF AGRICULTURE. 
He inverted 50 grams of air-dry sawdust with 150 c. c. of 0.5 per cent 
sulphuric acid (equivalent to 1.5 per cent of sulphuric acid based on 
air-dry wood) for one-half hour at 175° C, with 112 pounds of pressure 
to the square inch, and duplicate experiments showed yields of 20.4 
and 20 per cent of total sugars. The percentages of total sugars 
fermentable and the alcohol yields were not given. In the discussion 
of his results he gives the following: 
These experiments prove that one can work with small amounts of liquid without 
exerting a deleterious action on the yields. In fact, the yields in experiments 63 and 
64 (the two referred to above) are higher than in former ones in which larger amounts 
of liquids were used. At the same time, the extracts contained a greater percentage 
of sugar which is also favorable for fermentation. On the contrary, a small amount of 
liquid (acid solution) is not advisable, since in another experiment with sawdust and 
2 parts of liquid (0.5 per cent sulphuric acid) at 175° C. a considerable evolution of 
sulphur dioxide took place with partial cooking of the materials used. 
It must be remembered that the above experiments were made on 
50-gram samples of wood heated in an autoclave indirectly; whereas 
the results obtained at the Forest Products Laboratory were based 
on 100-pound samples cooked with steam. At the laboratory there 
was no coking in instantaneous or short-time cooks with 1 part of 
water to 1 of wood; although, with the higher acid concentrations, 
irrespective of the amount of water used, there was always some 
coking — that is, a darkening of the digested wood. When Neumann 
used sulphuric acid as the catalytic agent, he nearly always employed 
a 0.5 per cent solution and simply varied the amount. He thereby 
confused the effect of his ratios of water and acid to wood, since they 
were both varied simultaneously. 
If steam was used as the heating agent, of course some further 
dilution occurred during cooking; the more water used to begin with, 
the greater was this dilution. In an experimental apparatus, like that 
used at the Forest Products Laboratory, the amount of steam re- 
quired to heat the digester was greater in proportion to the amount 
necessary to heat the wood and acid solution than it would be in a 
large commercial digester holding two or more cords of wood. The 
following data from cooks Nos. 30 and 34 show in general how much 
this dilution was : 
Cook 30, 
June 30, 1914. 
Cook 34, 
July 29, 1914. 
Water 
per cent.. 
100. 
1.80 
0. 
7.5. 
38.48. 
271.20. 
103.55. 
103. 5. 
64.10. 
1. 62 to 1. 
125. 
H 2 S0 4 
do 
1.80. 
Minutes 
0. 
7.5. 
Blow-off (condensed) . . . 
Digested sawdust 
Dry wood 
pounds.. 
do.... 
do 
41.41. 
288.06. 
100.68. 
Water added 
..do.. 
126. 
Excess water in digested 
Ratio of water to wood i 
sawdust over 
n digested saw 
amount added 
dust 
do.... 
61.38. 
1.86 to 1. 
