GAS GENERATORS^19FIG.zinc for hydrogen, and ferrous sulphide for hydrogen sulphide, is
placed in the 300-cc. thick-walled genera-
tor bottle. The tubes are fitted as shown,
and in the drying tube is placed a plug
of cotton wool to strain the acid spray
out of the gas, or if the gas is to be dried,
granulated calcium chloride held in place
with a plug of cotton wool on either side.
Enough water is poured in through the
thistle tube to cover its lower end and
then about 5 cc. of 6iV HC1. The gas
begins to generate rather slowly, but if
one is impatient and adds more acid at
once the action will soon become so vio-
lent as to drive foam out through the
delivery tube. After a few minutes add
more acid, 1 cc. at a time, in order to keep
up the evolution of gas at the desired rate.
(b) Oxygen and Acetylene. The apparatus shown in Fig. 8 is
more suited for generating these
gases, which are produced by allow-
ing water to drip respectively on
sodium peroxide and calcium car-
bide. Remove the fittings from the
flask and place in it the required
amount of dry material. The sodi-
um peroxide to be used comes under
the trade name of " Oxone "; it has
been fused and then cracked into
good-sized lumps which are so hard
that they do not react with too
much violence with water. With
the fittings still removed from the
flask, fill the thistle tube with water,
open the pinch cock and allow the
vertical tube to become completely
filled, then close the pinch cock.
Replace the fittings in the flask.
Open the pinch cock cautiously to
let a single drop of water fall on the material. Note the effect,
Wooden Ring-FIG. 8