For the moisture, volatile
matter, fixed carbon and ash, the determinations are the same, but a
special distillation must be made to obtain a sufficient quantity of the
volatile products for subsequent examination. Take 500 or 1000 grams of
the well-sampled and powdered shale, and introduce into a cast-iron
retort as shown in fig. 74. Lute the joint with fire-clay, place the
cover on, and bolt it down. The bolts should have a covering of
fire-clay to protect them from the action of the fire. Place the retort
in a wind furnace, supporting it on a brick, and pack well around with
coke. Build up the furnace around and over the retort with loose
fire-bricks, and heat gradually.
[Illustration: FIG. 74.]
As soon as water begins to drip, the tube of the retort is cooled by
wrapping a wet cloth around it, and keeping wet with water. The water is
kept from running into the receiver by a ring of damp fire-clay. A
quantity of gas first comes over and will be lost, afterwards water and
oily matters. The retort must be red hot at the close of the
distillation, and when nothing more distils off, which occurs in about
two or three hours, the wet cloth is removed, and the tube heated with a
Bunsen burner to drive forward the matter condensed in it into the
receiver, and thus to clean the tube. It can be seen when the tube is
clean by looking up through it into the red-hot retort.
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