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° 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° will dissolve 41.14 volumes of oxygen; at 50°, 18.37 volumes; at 100° 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 familiar class of solutions, since in the laboratory substances are much more frequently used in the form of solutions than in the solid state.