REVIEWS The object of this departinent of theJoziriza1 is to issue, as $rolri$tly as possible, critical digests of all Jozir?ial articles which bear zipon any phase of Physical Chemistry. Gezeral The Evolution of Physical Theories since the XVII Century. P.Duhenz. Rev. Qziest. Sci. (Oct.) 1896. A very eloquent lecture. After the physics of the schoolmen, made up of comments upon the writings of Aristotle, scholars were led by Galileo to study nature at first hand. The subsequent Cartesian method, in disregarding the qualities of things, led to a belief that nothing exists but matter and motion ; after which the Newtonian school concerned itself with observable relations, paying no attention whatever to hypothetical metaphysical or mechanical causes. I n the present century the Cartesian mechanistics and the dynamism of Leibnitz are both suffering decline, largely through the influence of thermodynamics. But modern physics is a growth in which the labors of every individual inquirer have played a part. J. E. T. On Necessary and Unnecessary Application of Atomistics in Natural Science. P. Vo/olki.lrtann. Wied. A m . 61, 196 (1897). Physical phenomena may be roughly divided into three classes : Coarser phenomena, such. as those of elasticity or of capillarity, where the employment of atomistic hypotheses is unnecessary ; finer phenomena, such as those of electrolysis or of the dispersion and absorption of light, where atomistic hypotheses may be useful ; and a middle field where the usefulness of atomistics may be doubtful. Only in this latter field properly applies Boltzmann’s contention ( I , 434) that the application of both atomistic and phenomenological methods J . E. T. .should be developed together.
1
Reviews
677
Again on Atomistics. L . Boltznzaim. W e d . A m . 61, 790 (r897). Boltzmann expresses his agreement with the views of Volkmann-see preceding review-and restates his position, that all concepts of the calculus are of necessity based originally upon ( atomistic ) conceptions,-upon the initial consideration of a finite number of elements. J. E . T. Permanent Changes and Thermodynamics. I : The Perrnanent Changes of Systems which depend upon a Single Normal Variable. P.Duhenz. Zeit. phys. Chenz. 22,545 (r897). T h e state of such a system is determined by the therniodynaniic tetriperature T and a variable x (as e . g . the volume) so chosen that variation of Talone involves no production of work LK i. e. a ( normal variable). Then d’ TV= X d x when the outer condition X (as e. g.-f) maintains equilibrium, and we have E
=
+ - T . a+ja T
17 = -
a+ja T
where 8 , $- and are energy, free energy and entropy; also the condition of equilibrium X= a+jax, and for a path,-all these equations relating to a reversible series of states of equilibrium,-
Duhem now considers any possible change, and introduces the fundamental hypothesis that a function $ always exists such that e=+T . a+/aT, and that in an irreversible series of equilibria
where f is a uniform, finite, continuous function, and Jdxl is the. absolute value of dx. I n isothermal changes ( 5 ) becomes
dx= a y j a x z . dx +f.I ddY1 With rising x , dx = I dx 1 , so dxjdX = a*+iax. + f
,
while with falling x , dx = - 1 dx 1 and dXjdx = a . + / a x z
f.
-
.
Reviews
678
Putting a and /Ifor the tangents to these rising and falling isotherms in the X , x-plane there follows I/a
+ I/p=
2.
az+/ax. .
Also, assuming dX and dx to have the same sign in all isothermal ,changes-
a26jax. > 0 .
I n isobaric changes dX becomes zero in ( 5 ) , and so for rising .and falling x respectively-
(g
+f)dx
+g T d T =
o
The corresponding absorption of heat hdx is formulated, and, assuming this and d T to have the same sign, there follows 1.a*g/axaT
