Be ee ONT ss ee eee . 2 WE te eee ce Oe ee en are 
ee het wae sii: BS : t ey 
458 
Recently Jouniaux'® has determined the conditions of equilibrium 
at several temperatures between silver, hydrochloric acid gas, silver 
chloride and hydrogen, and has thus obtained the thermo-chemical 
equation, 
HCl (gas) + Ag = AgCl + H + 71 K*® 
Let us combine with this equation the following equations of Berthelot : 
HOI (gas) + Ag = H+ 1 +4174K. 
Ag a = AgCl + Ag +- 157 K. 
“i + 
4 Ag,O -- H = Ag -- 4 H,O + 52 K. 
H+}0=4H0+3 15K. 
Whence . 
2 Ag+ 0=2 Ag, 0+ 66 K (d). 
I have measured the E. M. F. of the following cell," 
| N | N | 
Hg Hg0 | KCl 4 KNO,j5 | AgNO,G9 | A 
and found it to be 0.429 — 0,00120t, volts, where t is the temperature 
Centigrade. From these figures the Helmholtz equation gives Hg + 
Cl + Ag = Ag + HgCl + Aq +175 Kk. With this equation we will 
combine the following : 
+ +. 
4 Ag,O + H = Ag -}-4H,O +52 K™ 
HgCl -- Cl == HgCl, + 219 K™ 
Hg + 2 Cl = HeCl, + 533 K” 
as +. : 
Cl+4H,0+Aq—Cl-+ H +40 +50 K.” 
Hence 4 
2 Ag+ O= Ag,0-+ 74 K (e). 
* O, R. (1903) 132, 1270. 
** | have added 3K to the value given by Jouniaux in order to obtain the “total” 
7 heat of reaction. 
“The details will be given in the following paper. 
* Thomsen gives 54 K, but Berthelot found 52 K by the neutralization of silver 
oxide by nitric acid (Ann. de Chim. (5) (1875) 4, 188), and also precipitation 
with alkalies (ibid (5) 41375) 4, 503) and has recently verified the value by 
new experiments (C. R. (1901) 133, 555). 
*'This value was obtained by Thomsen from the direct action of chlorine upon 
calomel. It is in all probability correct, as it has not been called into question 
i eo critical work on mercury salts of Nernst (Zeit. Phys. Chem. ipsa), ie 
1893) 120,- 620 and 921). rs 
ndependently by both Nernst and Varet (1. @.): 
K (Pogg. Ann. (1873). 148, 177). Berthelot’s is 
1 09, 546 and 590). Thomsen’s value is probably the more 
