The new chemistry / by Josiah P. Cooke, Jr.

  • Josiah P. Cooke
Date:
1876
Catalogue details

Licence: Public Domain Mark

Credit: The new chemistry / by Josiah P. Cooke, Jr. Source: Wellcome Collection.

    50/376 page 44
    energy is made rcanifest in many ways, especially in what we call the permanent tension of the gas. E^ery sm^l'ace in contact with a mass of gas is be- ing constantly bombarded by the molecules, and hence the great pressure which results, Now, it can easily be seen that, if the volume of the gas is diminished— that is, if the same number of molecules are crowded into a less space—they will strike more frequently against a given surface, and therefore exert a greater pressure. Moreover, it can readily be proved, although the mathematical demonstration would be out of place in a popular lecture, that the pressure must be inversely as the volume ; in other words, that the law of Mariotte is the necessary result of the molecular condition we have described. Another effect of molecular motion is that condi- tion of matter which the word temperatiu-e, just used, denotes. There are few scientific terms more difficult to define than this common word temperature. In ordinary language we apply the terms hot or cold to other bodies according as they are in a condition to impart heat to, or abstract it from, oiTr own, and the various degrees of hot or cold are what we call, in gen- eral, temperature. Two bodies have the same temper- ature if, when placed together, neither of them gives or loses heat; and, when, under the same conditions, one body loses while the other gains heat, that body which gives out heat is said to have the higher temperature. Increased temperature tested in this way is found to be accompanied by an increase of volume, and we employ this change of volume as the measure of tem- perature. This is the simple principle of a thermome- ter. The essential part of this instrument is a glass bulb, connected with a fine tube, and filled with mer
    digitised image 1
    digitised image 2
    digitised image 3