— 
— 
J. W. Gibbs— Equilibrium of Heterogeneous Substances. 451 
Gas-mixtures with convertible components.—The theory of the 
phases of dissipated energy of an ideal gas-mixture derives an 
especial interest from its possible application to the case of 
those gas-mixtures in which the chemical composition and 
resolution of the components can take place in the gas-mixture 
itself, and actually does take place, so that the quantities of 
the proximate components are entirely determined by the 
essure. se all 
mixtues with convertible components. If the general laws of 
f as-mixtures apply in any such case, it may easily be 
dissipated energy are the only phases 
the equation in p, ¢, #,, #2, ete. for the gas-mixture, regarding 
The validity of the results thus obtained depends upon the 
applicability of the laws of ideal gas-mixtures to cases in which 
chemical action takes place. Some of these laws are generally 
regarded as capable of such application, others are not so 
regarded. But it may be shown that in the very important 
case in which the components of a gas are convertible at certain 
temperatures, and not at others, the theory proposed may be 
established without other assumptions than such as are gen- 
erally admitted. = 
It is, however, only by experiments upon gas-mixtures with 
convertible components, that the validity of any theory con- 
cerning them can be satisfactorily established. : 
The vapor of the peroxide of nitrogen appears to be a mixture 
of two different vapors, of one of which the molecular formula is 
double that of the other. If we suppose that the vapor con- 
forms to the laws of an ideal gas-mixture in a state of dissipated 
energy, we may obtain an equation between the temperature, 
pressure, and density of the vapor, which exhibits a somewhat 
Striking agreement with the results of experiment 
Equilibrium of stressed solids.—The second paper commences 
With a discussion of the conditions of internal and external 
equilibrium for solids in contact with fluids with regard to all 
ssible states of strain of the solids. Tk 
. le ditions are 
uced by analytical processes from the general condition of 
