238 TRANSACTIONS OF THE 
should be carried out at as low a temperature as possible 
in order to recover an oil as little decomposed as possible, 
and which, commercially speaking, gives the maximum 
amount of refinable products. The hydrocarbons formed 
from kerogen, boil at a lower temperature by a decrease 
in the external pressure on the system and the use of 
steam or gas in accordance with the law of partial pres- 
sures, will give an effect similar to a reduced pressure 
or a vacuum. Generally speaking, the evaporation into 
a vacuum is, to a certain extent, a measure of the escaping 
tendency of the molecules of the liquid. Kinetic theory 
sets a superior limit to the rate of evaporation. 
“Evaporation is a rapid process approximating with- 
in, at most, one or two powers of ten the maximum rate 
of evaporation as calculable from kinetic theory. The 
apparently slow rate of evaporation is really due to the 
slowness of diffusion of the vapors from the liquid sur- 
face.’® The use of steam in the retort will increase the 
diffusion of the heavier hydrocarbon vapors, and because 
of the different characteristics of the different shales, 
the amount of steam used will likely vary with the shale 
being treated and the type of retort used. In addition, the 
use of steam, by lowering the partial pressure of the oil 
vapors, undoubtedly prevents, to a large extent, the con- 
densation of vapors which many believe takes place in 
the Scotch retort when the outgoing vapors come in 
contact with the incoming cool shale. Thus the use of 
steam largely prevents the condensation and redistillation 
of oil in the retort, which would undoubtedly take place 
without its use. 
Because of the scarcity of water in some of the shale 
regions, it has been proposed to re-use the water recov- 
ered during the retorting process. A large percentage 
of the water in the form of steam used in the retort will 
not be decomposed and will be condensed and collected 
with the hydrocarbon and other vapors. <A few experi- 
ments have been run where the untreated water recovered 
during previous retorting tests has been used to furnish 
retorting steam. The data available at the present time 
are not complete enough to warrant the drawing of defin- 
6Bouton, C. M., Personal communication. 
