The charge is well packed in the cylinder and provided with a
small fuse of cotton saturated with nitre. Fill the glass cylinder to
its mark with water and take the temperature with a thermometer marked
in degrees Fahrenheit. Ignite the fuse and immediately cover with the
outer copper cylinder (extinguisher-fashion), which will be held in its
place by the springs. The stop-cock should be closed before this is
done. Place the apparatus quickly in the cylinder of water. When the
action is over open the stop-cock and agitate the water by raising and
lowering the instrument a few times. Again take the temperature. The
rise in temperature, plus 10 per cent. for the heat used in warming the
apparatus and lost by radiation, gives the evaporative-power.
The following is an example:--
Temperature before experiment 67.0° F.
Temperature after " 79.0° "
--------
Rise 12.0° "
+ 1/10th 1.2° "
--------
Gives 13.2° "
One pound of the coal will evaporate 13.2 pounds of water.
SHALES, ETC.
The assay of these is carried out in the same way as that of coals, but
the volatile matters are separately examined, and, in consequence, a
larger quantity of material must be used.
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