ETHYL ALCOHOL FROM WOOD WASTE. 45 
From these figures it will be seen that all the material was equally 
cooked and gave practically the same yields, irrespective of size 
within the limits used. In addition, the material leached readily 
without formation of fine stuff, and 88.4 per cent of the sugar present 
was extracted without difficulty in three leachings. A certain 
amount of sawdust or material of similar size, therefore, seems 
necessary in order to obtain a good extraction, even though chips as 
large as five-eighths of an inch with the grain may be cooked under 
the conditions outlined in as short a time as 15 minutes and with 
good yields. 
It has been observed in commercial practice that a mixture of dust 
and chips in the proportion of 10 to 15 per cent of dust and 90 to 
85 per cent of chips gives the best results in the diffusion battery. 
If all dust or too much dust is used, the cooked material packs in 
the cells, high pressures are required to force the extracting water 
through it, and the material hangs in the cells at the time of dis- 
charge, causing loss of time in operation. If dust-free chips are used, 
the opposite is true; the extracting water percolates too fast, and 
extraction is not good. With the proper combination of dust and 
shredded chips, a 92 per cent extraction of the total sugar may be 
obtained. 
LEACHING EXPERIMENTS. 
The determination of the number of cells in a diffusion battery 
necessary to get a maximum extraction in a minimum time, with a 
minimum amount of water, is a very important point in this process. 
Furthermore, it was desirable to determine whether there was any 
selective solubility between the different sugars present or the soluble 
solids other than sugars. With this end in view, two series of cooks 
were made under the same conditions, viz, 125 per cent of water, 
2.5 per cent of sulphuric acid, a pressure of 7.5 atmospheres, and a 
cooking period of 15 minutes. It is regrettable that an accident to 
some of the condensing apparatus prevented blowing off these cooks, 
and after each cook it was necessary to allow the digester to cool 
gradually to 212° F. or less before the contents were discharged. 
Undoubtedly reducing substances were formed and retained which 
were the cause of erratic sugar data being obtained. 
Cooks Nos. 51 and 52 were preliminary and were made for the 
purpose of outlining a method of procedure. The digested sawdust 
from both cooks was put into the leaching tanks and successively 
leached by sprinkling small quantities of boiling water over the 
digested sawdust and collecting the drip as soon as it had drained 
through the sawdust. The different extracts were then analyzed, 
neutralized, and fermented in the usual manner with the following 
results. 
