UTAH ACADEMY OF SCIENCES 237 
Present knowledge of the pyrolytic distillation of the 
kerogen—the source of the oil—in the shale indicates 
that the dead vapor space within the retort should be 
reduced to a minimum. Excessive decomposition or 
cracking results when the vapors are allowed to stagnate 
or form eddy currents in hot pockets. Good oil can be 
recovered from small laboratory and assay retorts where 
comparatively fine ground shale is used and the vapor 
space reduced to a minimum by carefully filling the 
retort to its maximum capacity, but for large scale con- 
tinuous commercial operation some form of gaseous 
sweeper or scavenger probably will have to be used in 
order to clear the vapors from the larger interstices and 
dead vapor pockets which form constantly during a con- 
tinuous movement of the shale mass and the use of steam 
or the uncondensible gases recovered during the retorting 
process will probably prove one of the most successful 
means of increasing the velocity of the hot hydrocarbon 
vapors distilling from the shale column. 
In the sixth purpose enumerated, steam serves an- 
other important function during the distillation process 
by decreasing the partial vapor pressure of the heavier 
hydrocarbons. There is little doubt but that the boiling 
point of the kerogen of the shale is above the decompo- 
sition or cracking temperature of the hydrocarbons pro- 
duced, and since cracking is a dehydrogenation process, 
it seems hardly possible to secure a good saturated 
paraffin base oil from a retort where excessive thermal 
decomposition of the vapors takes place. Microscopic 
study of the decomposition of the kerogen under the influ- 
ence of heat shows that the solid kerogen first softens or 
melts and then vaporizes. Generally speaking, the tem- 
perature at which an oil dissociates or cracks, depends 
mainly on its molecular weight and constitution; and 
speaking broadly, the more complicated the molecule, the 
easier it undergoes dissolution, and also the more unsatur- 
ated the compound, the more easy it disintegrates. The 
velocity of the dissociation reactions during cracking is 
greatly dependent upon the temperature, and even a 
slight increase in temperature may greatly accelerate the 
dissociation reaction. In other words, the distillation 
