34 QUANTITATIVE ASPECTS OF CHEMISTRYized, without decomposition, at a temperature which will permit
the accurate measurement of the volume occupied by a given
weight of substance. If the pressure and temperature of the
determination are also known, this volume can be reduced to stand-
ard conditions, and the weight, which would be required to fill
22.4 liters under standard conditions, calculated. This weight
in grams is the molecular weight.
In the following experiment we shall use carbon tetraehloride
as the " unknown " substance, the molecular weight of which is
to be found.
Materials: pure carbon tetraehloride, 12 cc.
Apparatus: Dumas bulb (250-cc. bulb with neck drawn to a
capillary).
600-cc. beaker.
250° thermometer.
2 Bunsen burners,
burette clamp. „
wire holder and cover,
unglazed porcelain chips.
4-inch iron ring and ring stand,
cork stopper, split.
Data Form:
Weight of the open Dumas bulb filled with
air (a) grams
Weight of the sealed Dumas bulb filled with
CCU vapor (6) grams
Weight of the Dumas bulb filled with water (c).. grams
Barometric pressure mm.
Temperature of the boiling water bath °
Room temperature °Procedure: Weigh accurately a clean, dry Dumas bulb. Intro-
duce into it about 12 cc. of carbon tetraehloride by warming the
bulb and allowing it to cool with the tip dipping into the liquid.
Heat about 300 cc. of water to approximately 50° in a 600-cc.
beaker. Drop a few pieces of porous tile into the beaker, so that
the water will boil without " bumping." Immerse the bulb in the
water, and hold it in this position by putting the wire holder around
the neck of the bulb. Cover the beaker, and clamp the upper end