Synthetic Inorganic Chemistry

(^20) NOTES ON LABORATORY MANIPULATION
and thereafter let the water in, a single drop at a time, to obtain
the desired flow of gas.
(c) Automatic Gas Generator for Carbon Dioxide, Hydrogen and
Hydrogen Sulphide. The apparatus shown in Fig. 9 is based on
the principle of the familiar Kipp generator, and it is especially
applicable if a solution is to be saturated with the gas in question,
as, for example, when an ammoniacal solution of common salt
is to be saturated with carbon dioxide in the preparation of
sodium bicarbonate by the Solvay process.
FIG. 9
Assemble the apparatus as shown in the diagram. The stem
of the generator tube E should reach flush with the bottom of the
stopper but not below. The delivery tube C should reach nearly
to the bottom of the generator bottle D. Place the requisite
amount of calcium carbonate (or zinc, or ferrous sulphide) in the
generator tube. Then insert a loose plug of glass wool F about
1| inches long so that it will stand about midway between the
top of the solid material and the stopper in the mouth of the tube,
and act as a gas filter (to remove acid spray). Pour the requisite
amount of acid into the reservoir A; clamp the reservoir at just
the same height as the generator tube, and pour in water cautiously