The receiver is
then removed, and the retort, taken from the furnace, is allowed to
cool. When cold it is opened, and the fixed carbon and ash weighed, as a
check on the smaller assay.
The distillate of water and oil is warmed, and will separate into two
layers, the upper one of which is oil, and the lower water. These are
measured, and if the specific gravity of the oil is taken, its weight
may be calculated. If the two liquids do not separate well, the water
may be filtered off, after cooling, through a damped filter. The
separation is, however, best effected in a separator (fig. 75). The
liquids are poured into this, allowed to settle, and the lower layer
drained off. The volume of the water is measured and its weight
calculated in per cents. on the amount of shale taken.
[Illustration: FIG. 75.]
~Examination of the Oil.~--A sufficient quantity of the oil must be got,
so that if one distillation does not yield enough, the requisite
quantity must be obtained by making two or more distillations. The oils
are mixed, and the mixture, after having had its volume and specific
gravity ascertained, is placed in a copper retort, and re-distilled with
the aid of a current of steam. The residue in the retort is coke.
The distillate is separated from the water by means of the separator,
and shaken for ten minutes with one-twentieth of its bulk of sulphuric
acid (sp.
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