Gay-Lussac found that, when 100 volumes of gas or air me heated from to F., they become 137k volumes ; or the increase is for each degree of Fahrenheit. This law has supplied a simple rule for determin. ing what the known bulk of a gas at any tem perature will be at any other temperature. Suppose, for example, it is desired to know what the bulk of 100 cubic inches of air at will be at 60° : subtract 32 from 480, the remainder is 448; to which add the degrees above zero indicating the temperature of the air ; these are and 60°, making 480 an i 508. Then say 480: 508 :: 100: 105.832 the volume of the air at 60°.
Air suffers diminution of volume in propor portion to the pressure to which it is subjected, and the same law holds good with all the more incondensible gases.
The solubility of gases in water is extremely various. Dr. Henry ascertained that the volume of each gas absorbed by water is the same, whatever be the pressure to which the gas is previously subjected. 100 volumes of water will absorb 450 volumes of cyanogen ; whereas the absorption of hydrogen is only 2 volumes. In general, the more easily a gas is condensable by cold and pressure, the more soluble it is in water. Gases are also absorbed by charcoal and other porous bodies, the ab sorption being in ammonia 90 times the vo lume of the absorbent, and in hydrogen 1.75 times.
Some gases are more soluble in water than others ; and some are more readily absorbed than others by porous substances. Dr. Faraday
has liquefied some gases and solidified others. The method which he employed consisted in combining the condensing powers of mechani cal compression with that of very considerable depression of temperature. The first object was attained by the successive action of two air-pumps. The tubes into which the air, thus condensed, was made to pass were of green bottle-glass, and had a curvature at one portion of their length adapted to immersion in a cooling mixture : they were provided with suitable stopcocks, screws, connecting pieces, and terminal caps, sufficiently air-tight to sustain a pressure of 50 atmospheres. Cold was applied to the curved portions of the tube by their immersion in a bath of Thirolier's mixture of solid carbonic acid and ether. The degree of cold thus produced, when the mix ture was surrounded by the air, was — 106° Fah., by an alcohol thermometer ; but when placed in vacuo, the thermometer indicated 166° below zero. Without the aid of me chanical pressure, Faraday liquefied sulphur ous acid gas, cyanogen, chlorine, ammoniacal gas, hydro-sulphuric acid gas, carbonic acid, hydrochloric acid, and nitrous oxide. With the combined aid of cold and pressure he liquefied sulphuretted hydrogen, arse niuretted hydrogen, hydrioclie acid, hyro bromic acid, nitric oxide, fluosilicon, and °de fiant gas. Alcohol, ether, and chlorine have not yet been solidified ; oxygen, hydrogen, nitrogen, and carbonic oxide have neither been solidified nor liquefied.