ETHYL ALCOHOL FROM WOOD WASTE. 
EFFECT OF TANNIN AND BARK. 
53 
Various mixtures of spruce and spruce bark were cooked under 
the usual conditions of 7.5 atmospheres of pressure, 125 per cent 
of water, and 2.5 per cent of sulphuric acid based on dry weight. 
The results are given in the following table : 
Cook 
No. 
Total 
sugars 
(per cent 
of origi- 
nal dry- 
weight). 
Per cent 
of total 
sugars 
fermen- 
table. 
Alcohol yields. 
Per cent 
• of origi- 
nal dry 
weight. 
Gallons 
absolute 
per dry 
ton. 
84 
87 
85 
88 
22.11 
19.60 
22.49 
17 07 
70.38 
69.47 
60.04 
31.95 
7.457 
6.765 
6.364 
2.730 
22.55 
91.5 per cent of wood, 8.5 per cent of bark 
74.5 per cent of wood, 25.5 per cent of bark 
All bark 
20.46 
19.25 
8. 25 
From the result it is seen that as much as 25 per cent of spruce 
bark may be mixed with the wood without appreciably decreasing 
the yield of alcohol. Other barks were not available in sufficient 
quantity to determine the practical limits to which they may occur 
in waste mixtures without appreciable effect. Commercial experience 
however, has shown that not more than 10 per cent of the total of 
yellow pine may be bark without seriously affecting the yield. Spruce 
bark has long been used in Europe as a tanning material and has 
found favor because of its high sugar content, which in the "mellow- 
ing" or fermentation and acidification of the tanning liquors produced 
a comparatively large amount of acid and was therefore used as a 
plumping agent. 
The tannin present shows no inhibitory action toward yeast growth, 
for even sugar liquors produced from red and white oak gave normal 
fermentation and fermentation efficiencies. In commercial practice 
other factors have been found, such as long cooking periods with 
increased formations of acids, acetone, and aldehydes, which influence 
yeast growth and fermentation much more than does the tannin 
found in the sugar liquors usually produced from mill waste. 
EFFECT OF CATALYZERS OTHER THAN SULPHURIC ACID OR IN ADDITION 
THERETO. 
As indicated previously, Korner, Cohoe, and others have attempted 
the production of sugar and alcohol from wood with the use of hydro- 
gen peroxide, potassium dichromate, and potassium persulphate 
as hydrating and oxidizing agents in addition to sulphuric acid, and 
these investigators have also recommended the use of hydrochloric 
acid. The experiments at the Forest Products Laboratory have 
been only preliminary to an investigation of the field, but they have 
confirmed several known facts besides establishing several new ones. 
