CLAUSIUS, R. (RUDOLF). - AVOGADRO'S HYPOTHESIS CONFIRMED AND EVAPORATION EXPLAINED.

Ueber die Art der Bewegung, welche wir Wärme nennen.

(Leipzig, Johann Ambrosius Barth, 1857). Without wrappers in "Annalen der Physik und Chemie. Hrsg. von J.C. Poggendorff", Vierte Reihe Bd.10, Stück 3 (= Poggendorff Bd. 100, No. 3). Pp. 353-480 a. 1 plates (the entire "Heft" (Stück) 3 offered). Clausius's paper: pp. 353-380. Clean and fine.

First printing of a milestone paper in the Kinetic Theory of Gases in which Clausius gives the physical explanation for the evaporation of a liquid and presents the first physical argument in support of Avogadro's hypothesis that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules.

"In the paper "Ueber die Art der Bewegung, welche wir Wärme nennen.", Rudolf Clausius (1822-1888) established mathematically that the heat in a gas cannot be accounted for exclusively by translational motion of the molecules and asserts that molecules have rotational and vibratiional motion as well as translational motion. He consequently rejects the contentions the the translational kinetic energy is conserved during molecular collisions and that all molecules have equal, constant velocities. His allowancee for differing molecule velocities enables him to offer a new explanation of evaporation, asserting that he molecules able to overcome the attractive forces of the liquid and "escape" to the gaseous state are those with high velocities (and hence high kinetic energies). hence evaporation produces a loss of energy in the liquid and a decreasein temperature."(Parkinson in "Breakthroughs", 1857 C/P).

"This 1857 paper (the paper offered) also marked another importent beginning in physical theory, for it presented the first physical argument in support of Avogadro's hypothesis that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules. Clausius argued that if it were assumed that all types of molecules possess the same translational energy at equal temperatures, then, since all gases have the same relationship between pressure, volume, and temperature, they would necessartly contain equal numbers of molecules in equal volumes at the same temperatur and pressure. Avogadro's hypothesis, therefore, found support in the mechanical theory of heat, independently of the usual chemical arguments."(DSB III, p. 307).

Order-nr.: 43060