ro of ee F, MOP Mi Malt Delt A rs 
452 
0.06; the fourth term, — 0.11. Combining these, we get for the second 
term the value 2.36, whence U, is 13,600 in small calories. 
Using similarly values (a) and (c) we find for U, the same. value, 
13,600 calories. 
From values (0) and (c) we find U, = 13,300. This value is to be 
given less credit on account of the nearness of the two temperatures used. 
The remarkably good agreement between these values shows conclu- 
sively that we are dealing with the same reaction throughout the whole 
range of temperature from 302° to 445°. As final result we will take, 
U, = 13,600 small calories, or 136 K (Ostwald calories). From 
equation 3 the value of U at room temperatures is therefore between 
127 K and 128 K. This is the increase of internal energy accompany- 
ing the decomposition of 2-gram molecules of silver oxide. ‘The heat 
of formation of silver oxide at room temperatures, exclusive of external 
work, is therefore one-half this value or 64 K. 
HEAT OF FORMATION OF SILVER OXIDE, OTHERWISE DETERMINED. 
For the heat of formation of silver oxide we find in the literature only 
two determinations which are at all trustworthy. Thomsen” allowed 
copper to act upon silver nitrate and from the heat of this reaction, the 
heat of formation of copper nitrate, and the heat of neutralization of 
silver oxide, calculated the heat of formation of the latter to be 59 K 
(a). Berthelot*! by a similar method obtained 70 K (b).” 
In his experiments on the energetics of galvanic elements, Jahn‘ 
obtained the following equation : 
Pb + 2 AgNO,, Aq = Pb (NO,),, Aq + 2 Ag+ 509 K. 
Let us combine this equation with the following: 
PbO + 2 HNO,, Aq = Pb(NO,),, Aq + H,O + 178K (Thomsen ) 
Pb -+ O = PbO + 503 K (Thomsen) 
Ag,O -| 2HNO,, Aq = H,0 + 2 AgNO,, Aq + 104 K™ (Berthelot) 
Whence 
2 Ag+ 0 = Ag,0 + 68 K (c) 
” Not having Thomsen’s book at hand, the values here attributed to him are 
taken from Ostwald’s Lehrbuch. 
™ Ann. de Chim. (1878) 15, 186. 
12 All these values are for the “total” heats of reaction. I have chosen to use 
these values, which include the external work, since they are the ones commonly 
given in the literature. The reduction to the simple “internal” heat of reaction 
will be made later. 
18 Wied. Ann. (1886) 28, 493. 
™ This value will be discussed presently. 
