A system of physical chemistry - Index of


A system of physical chemistry - Index of



The accompanying figure (Fig. 12) shows diagrammatically the

relative variation of U and A. It will be observed that, in this reaction,

the affinity increases with increase in temperature, whilst the heat

effect or total energy change decreases.

Fig. 12.


A. Magnus {Zeitsch. Elektrochem., 16, 273, 1910) has carried out a

^milar investigation of the reaction—

Pb + 2AgCl-^PbCl2 + 2Ag

in which the affinity was found to decrease as the temperature was


Mass Action Equilibrium in Solutions from the Standpoint of

Infra-red Radiation.

{Cf.Y. Kriiger, Zeitsch. Elektrochem., V7, 453, 1911.)

The problem to be considered is the relation of the ionisation con-

stant of the solute to the dielectric constant of the solvent.

The radiation density in a medium depends upon the cube of the

refractive index n as well as upon other factors. Further, on the basis

of the classical electro-magnetic theory of light, the refractive index is

connected with the dielectric constant D by the relation n^ = D.

Hence the radiation density is proportional to the dielectric constant

raised to the power 3/2. It follows that in media of high dielectric con-

stant, such as water, the radiation density is correspondingly high.

Thus, D for water is approximately 81, and 8i^"^ = 730. Hence for

long waves, the radiation density in water at ordinary temperatures is

730 times the radiation density in a vacuum, where D = i. Kriiger

considers the case of a dissolved electrolyte, and assumes that only a

fraction of all the ions vibrate, but that those which do vibrate at all

possess the theoretical amount of vibrational energy required by classical

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