ETHYL ALCOHOL FROM WOOD WASTE. 19 
acid, fixed and volatile; on the first distillate, which gave acetic and 
formic acid; and on the second distillate, which gave acetic acid 
only. 
After the proper samples had been taken, the digested sawdust 
was placed in the leaching tank, where the sugar was extracted from 
it with a number of portions of warm water. The liquor from the 
digester and centrifugal (whenever there was any) and the leach 
liquors were then combiued, neutralized with calcium carbonate and 
allowed to settle. After settling, the clear liquor was decanted and 
concentrated to a heavy sirup in a single-effect vacuum evaporator. 
These sirups were saved until the concentrates from two or three 
runs were obtained, and then they were diluted to proper strength 
for fermentation. 
YEASTING AND FERMENTATION. 
The yeast used was a pure-culture strain of Saccharomyces cere- 
visize isolated from a yeast used in a Hungarian distillery producing 
alcohol from beet-sugar molasses. This yeast is well adapted to 
the fermentation of sugar solutions obtained from the hydrolysis of 
wood and is considered to be the best strain available for this pur- 
pose. 
The yeast was propagated in a beer wort, which was made up as 
follows: To 100 parts of water, 3 parts of hops were added, and the 
mixture was boiled vigorously for 15 minutes. The hops were fil- 
tered off while hot and from 25 to 35 parts of ground barley malt 
were added. The mixture was kept at 70° C. for four or five hours 
imtil the starch had all been converted, as shown by the iodine test. 
The malt was then pressed off and the liquid filtered. The filtrate 
polarized 18° to 20° in a saccharimeter. One liter was then put into 
a 2 or 5 liter cotton-plugged Erlenmeyer flask and sterilized in an 
Arnold sterilizer on three successive days. A small drop of the cul- 
ture yeast kept in sterile sugar solution was added, and the fermen- 
tation was allowed to go to completion in about four or five days at 
30° C, after which the resulting beer was poured off the yeast, and 
a 10 per cent sterile sucrose solution was added. About 10 c. c. of 
the yeast solution was then placed in a 50 c. c. sterile Florence flask, 
and these samples were used for starting the yeast. All transfers 
were made and similar work was done in a Hansen culture cabinet 
under sterile conditions. 
The more recent practice for control work at the Forest Products 
Laboratory has been to propagate the yeast in a Pasteur flask in beer 
wort made as above, from which it is transferred to Freudenreich 
flasks which have side necks. Under these conditions it has been 
possible to propagate a yeast of strict purity, and all possible sources 
of contamination have been eliminated. The yeast will keep for long 
