Water is the only liquid the action of which upon the gases has been accurately examined. In its ordinary state it contains in solution a considerable portion of atmospheric air, which can be separated from it by boiling; and it is then capable of re-absorbing air, and any other gaseous fluid with which it may come in contact. All gases, however, are not equally absorbable; some being taken up in great quantity, and others only in a very small proportion.

1 Thomson's Chymistry, 4th edit. iii. 469.

Table of pharmaceutical gases which are but little absorbable by water, placed in the order of their absorption, beginning with the least absorbable.

1. Nitrogen gas.

2. Hydrogen gas.

3. Arsenical hydrogen.

4. Carbureted hydrogen.

5. Oxygen gas.

6. Nitrous gas.

7. Olefiant gas.

The quantity of any gas absorbed by water is very much increased by pressure; but by diminishing pressure, the gas again separates in its elastic form. Temperature also regulates the quantity, which diminishes as the temperature increases, owing to every additional increment of caloric augmenting the elasticity of the aeriform fluid. Thus Dr. Henry found that 100 inches of water at 55° absorb 108 inches of carbonic acid, while at 85° they absorb only 84 inches.

When water is pure, and the pressure and the temperature are equal, it then "absorbs a determinate quantity of every individual gas."

Table, Exhibiting The Bulk Of Several Gases, Absorbed By 100 Cubic Inches Of Water At 60&Deg;, According To The Experiments Of Mr. Dalton, Dr. Henry, And M. Saussure

1 Thomson's Chymistry, 5th edit. iii. 58.

From this table it appears that water absorbs its own bulk, or rather more, of the first three gases; one eighth of its bulk of the fourth; one twenty-seventh of the fifth, sixth, and seventh; and one sixty-fourth of the last three; and the absorption is in the direct ratio of the densities of the gases.

With regard to pressure, water of the same temperature always takes up the same bulk of each gas, whatever be the density of the gas; and, therefore, by increasing the pressure sufficiently, water may be made to absorb any quantity of gas. Thus twice its bulk of carbonic acid will be absorbed under an additional pressure of 30 inches of mercury; three times its bulk under a pressure of 60 inches, and so on: - a fact which has been applied to practice, in the manufacture of aerated soda water, on a great scale. From this circumstance it would appear that the absorbed gas still retains its elasticity; yet it is probable that a chymical attraction is exerted between the particles of the water and those of the gas, and it is taken up until the repulsion between the particles of the absorbed gas just balances the affinity of the water for them. Owing, however, to the weak affinity exerted between the gas and the water, if a quantity of water fully impregnated with any gas, as carbonic acid, for example, be exposed to the atmosphere, or any other gaseous body, the greater part of the absorbed gas escapes from the water and mixes with the superincumbent air; and, therefore, to preserve the impregnation complete, the aerated water must be preserved in well-stopped bottles, or under an atmosphere of the same gas it contains.

Such are the principal circumstances connected with the absorption of the less absorbable gases; those which are more absorbable appear to belong to the class of acids and alkalies.

Table Of The Very Absorbable Gases, With The Numbers Of Measures Of Each Absorbed By One Measure Of Pure Water; And The Increase Of Bulk Produced On The Fluid, Supposing The Original Bulk To Be

1 Thomson's Chymistry, 5th edit. iii. 68.

The absorption of these gases is the consequence of the exertion of an affinity between them and water; but, in every respect, the circumstances attending it are exactly the same as those attending the absorption of the former class of gases; except that "most of the gases belonging to the first class experience an expansion when absorbed; while all those of the second undergo a condensation, their affinity for water being greater than their elasticity."

With regard to the absorption of gases by other liquids, scarcely any very decisive experiments have been made; but the experiments of Saussure render it probable that alcohol and oil absorb a much greater proportion than water.