212 TRANSACTIONS OF THE 
affect the partial pressures of the hydrocarbon vapors 
evolved from the kerogen, probably to the improvement 
of the quality of the oil distillates. Carbonates as well 
as sulphides, begin to decompose within this range of 
temperatures and the concentration of the gases pro- 
duced may alter the chemical constitution of the oils pro- 
duced from the kerogen. The mineral aggregation of 
the spent shale may be difficultly penetrated by the 
escaping oil vapors as they work their way from the 
inside of the distilling shale lump to the surface, and 
hence pressures will develop within the shale pieces 
with the result that the oil vapors will escape at higher 
temperatures than is necessary for their formation; con- 
ditions conducive to unregulated decomposition of the 
oil. These are a few of many possible effects on the 
products of decomposition of the kerogen that may be 
caused by the presence of the mineral matter of the 
shales, and consequently, results are very difficult to pre- 
dict when new and unfamiliar shales are being destruc- 
tively distilled. 
EXPERIMENTAL METHODS OF THE BUREAU OF MINES. 
The individual problems of destructive distillation 
or the retorting of oil-shales, therefore, must be solved, 
largely, by “cut” and “try”? methods. In the research 
work of the Bureau of Mines, oil-shales are treated in 
various states of fineness and under many conditions in 
which the temperature, duration, rate and method of 
supplying heat are varied. Conditions are brought about 
wherein the atmosphere surrounding the shale, while it 
is distilling, is made to contain definite proportions of 
certain auxiliary gases and vapors, which are used for 
their chemical influences and as scavenging mediums. 
The gases and oils evolved during distillation are caught 
and analyzed, and their properties are tabulated against 
the known conditions under which they were produced. 
The accumulation of data pertaining to any shale can be’ 
correlated finally and data valuable for use in the design 
of retorts is thereby obtained, wherein correct principles 
of chemistry, thermo-dynamics, and engineering prac- 
tice may be employed. 
