451 
and is undoubtedly much smaller at the temperature of our experiments, 
the first assumption will not lead to any appreciable error. The second 
assumption would also be justifiable if it were not for the fact that 
in our experiments at 445° the pressure is so great, and consequently 
the volume v so small, that in comparison with it V is large enough to 
be considered. 
Regarding V not as a negligible but as a constant quantity and 
assuming that py = RT, I have succeeded in obtaining the following 
integrated form of equation 4, 
Poa meats RAT” T. ee 
With the aid of this equation we are able to calculate from the decompo- 
sition pressures at any two temperatures the value of U,. In order to do 
this we must know the values of V and C. The terms in which these 
quantities occur are comparatively unimportant ones in the equation and 
since both these quantities can be disregarded altogether without very 
seriously influencing the result, their approximate values will suffice. 
From the tables of Landolt and Bornstein we find for the densities of 
silver and silver oxide 10.5 and 7.5, respectively. Calculating from 
these the molecular volumes we get approximately 20 ec. as the value of V. 
The specific heat of silver oxide has not been determined, but the value 
of C may be found from the principle of the constancy of the atomic 
heat in solids. The heat capacity of silver is doubtless approximately 
the same in the oxide and in the metal. ©, therefore, is the difference 
between the heat capacity of oxygen in the gaseous and solid states. The 
heat capacity at constant volume of 32 grams of oxygen in the gaseous 
state is 5 calories per degree. The heat capacity im the solid state 
is about 8.°. Whence C equals 3. 
We will determine the value of U, in calories and therefore use for 
R the value 2.0, except in the next to the last term of equation 5, in 
which, if the pressure is expressed in atmospheres and the volume in 
cubic centimeters, R must be expressed in corresponding units and given 
the value 83. . 
We have three sets of experimental values (a) T= 445 + 273, 
p= 207; (6) T = 302 + 273, p = 20.5; (c) T = 325 + 273, p = 82. 
These may be used in equation 5 in pairs. Using values (a) and (b) the 
first term of the equation, Jn 4 has the value 2.31; the third term, 
2 
*This equation may readily be verified by differentiating it. The resulting 
equation by suitable transposition and with the aid of the equation pv.—=RT, 
can readily be shown to be identical with equation 4. Equation 5 may also be 
obtained by an independent method from equations 6 and 7 of my paper entitled 
“Law of Physico-Chemical Change.” (Zeit. Phys. Chem. (1901) 38, 205.) 
* See, for example, Ostwald’s Lehrbuch. 
