Synthetic Inorganic Chemistry

(^200) ALKALI AND ALKALINE EARTH METALS
At the equilibrium point of this reaction the partial pressure of
carbon monoxide is many times that of the carbon dioxide;
thus it would be much above 1 atmosphere, and carbon monox-
ide would escape from the crucible. With excess powdered char-
coal in the crucible, therefore, both reactions would continue
to run until all the barium carbonate had changed to barium
oxide. Carbon monoxide does not react with barium oxide.
In the following procedure, in addition to the charcoal, a little
rosin is mixed with the charge. On heating, the rosin decomposes
forming finely divided carbon which becomes very intimately
mixed with the charge.
Temperature
700°
750
800
897
1000
1100
1350
Pressure of CO2 in
equilibrium with
CaCO 3
22 mm.
80
167
760
8740
BaCOs
2.7 mm.
381.
The barium oxide obtained in this way is not pure, but contains
particles of charcoal as well as impurities coming from the mineral.
It is very suitable, however, for the manufacture of barium hy-
droxide, into which it is converted by treatment with water.
Barium hydroxide is extremely soluble in hot water, but sparingly
so in cold water, from which it separates in flake-like crystals of
the composition Ba(OH) 2 -8H 2 O.
Materials: barium carbonate, BaCO 3 , 99 grams = 0.5 F.W.; if
the mineral witherite is used it should be very
finely powdered; the artificially prepared mate-
rial will react more readily,
powdered charcoal, 25 grams,
rosin, 5 grams.
Apparatus: gas furnace.
30-gram clay crucible, with cover.
8-inch porcelain dish.