Synthetic Inorganic Chemistry

WEIGHT OF A LITER OF OXYGEN^27

about 2 grams of dry powdered potassium chlorate and again
weigh it accurately. (The potassium chlorate must be finely powd-
ered and thoroughly dried. Use the material which has been
especially prepared for this experiment. It will be found in the
balance room.) Connect the tube to the apparatus. Dip the
capillary jet in a beaker of water, and raise the beaker until the
surface of the water is at the same level in the beaker and in
the flask. Open the cock until water has run in or out to equalize
the pressure. Then close the cock. In this way the air in the
apparatus at the start is at atmospheric pressure. At the end it

or

Ring

Elbow Tube^

Pyrex T&bey^r^

Potassium

Chlorate

Ring Stand

M

HK

BuretteClamp

I!

7

I

J

I

1 'l

r 1

Large

Beaker*

FIG. 10

must be brought to the same pressure, so that the two volumes
are directly comparable. Note: It is important that the flexible
rubber tube be filled completely with water; otherwise, when the
levels are equalized, there will be a column of air in one part and
a column of water in another part of the tube and the pressure on
the gas in the flask will not be the same as that of the atmosphere
on the water in the beaker. Empty the beaker and weigh it on
the platform balance (do not use the analytical balance) without
drying it. Hold the jet pointing into the beaker so that the
water may be seen dripping into it, and thus the rate of the pro-
duction of gas regulated. Open the pinch cock and commence
heating the potassium chlorate, so that a steady, but not a rapid,
stream of water runs from the jet. Heat slowly to avoid exces-
sive pressure and to prevent the entrainment of finely divided