y
supposing a vessel B (Fig. 30), to be filled with the gas and inverted
over the liquid. Under these circumstances the gas cannot escape or
become mixed with another gas.

~Circumstances affecting the solubility of gases.~ A number of
circumstances affect the solubility of a gas in a liquid.

1. _Nature of the gas._ Other conditions being equal, each gas has its
own peculiar solubility, just as it has its own special taste or odor.
The solubility of gases varies between wide limits, as will be seen from
the following table, but as a rule a given volume of a liquid will not
dissolve more than two or three times its own volume of a gas.

_Solubility of Gases in Water_

1 l. of water at 760 mm. pressure and at 0 deg. will dissolve:

Ammonia 1148.00 l.
Hydrochloric acid 503.00
Sulphur dioxide 79.79
Carbon dioxide 1.80
Oxygen 41.14 cc.
Hydrogen 21.15
Nitrogen 20.03

In the case of very soluble gases, such as the first three in the table,
it is probable that chemical combination between the liquid and the gas
takes place.

2. _Nature of the liquid._ The character of the liquid has much
influence upon the solubility of a gas. Water, alcohol, and ether have
each its own peculiar solvent power. From the solubility of a gas in
water, no prediction can be made as to its solubility in other liquids.

3. _Influence of pressure._ It has been found that the weight of gas
which dissolves in a given case is proportional to the pressure exerted
upon the gas. If the pressure is doubled, the weight of gas going into
solution is doubled; if the pressure is diminished to one half of its
original value, half of the dissolved gas will escape. Under high
pressure, large quantities of gas can be dissolved in a liquid, and when
the pressure is removed the gas escapes, causing the liquid to foam or
_effervesce_.

4. _Influence of temperature._ In general, the lower the temperature of
the liquid, the larger the quantity of gas which it can dissolve. 1000
volumes of water at 0 deg. will dissolve 41.14 volumes of oxygen; at 50 deg.,
18.37 volumes; at 100 deg. none at all. While most gases can be expelled
from a liquid by boiling the solution, some cannot. For example, it is
not possible to expel hydrochloric acid gas completely from its solution
by boiling.

SOLUTION OF SOLIDS IN LIQUIDS

This is the most