92 A. P. MATHEWS 



obtained by the difference between E and the second term. For 

 example, a silver plate in contact with a normal ionic silver nitrate 

 solution shows a difference of potential between itself and the solution 

 of +1.048 volts. .'.=+1.048 volts. c 2 is the concentration of 

 silver atoms in metallic silver. One gram atom of silver i. e., 107 .9 



TABLE 2. 



THE IONIC POTENTIALS OF THE IONS OF METALS IN VOLTS. 

 K -2.92(7) Cd -0.089 0-0.426 



Na-2. 54 (?) Fe" + o.oo Cl-i.6 94 (?) 



Li 2-32(?) Co +0.107 Br i. 270(7) 



Ba -2.54(7) Ni +0.112 I - o . 797(7) 



Ca -2.26(?) Pb +0.179 



Sr -2. (?) H +o.io7(?) 



Mg 1.160 Cu +0.668 



Mn 0.737 Hg +1.080 



Zn -0.434 Ag +1.163 



grams of silver occupies the space at 18 of 10.1 c.c. ; i.e., the 

 atomic weight in grams divided by the specific gravity. c 2 , or 



the number of gram atoms of silver in one liter of silver, = . c 3 



= i, since the concentration of silver ions is one gram ion per liter. 

 Substituting these values in (i), 



, c 2 , 10.1 



i .048 volts= 0.057 *g 7^ + -57 lg 



C 1000 



or 



, c z 

 1.163=0.057 log- . 



There is hence a difference of potential of 1.163 v lts between one 

 atom of silver and one ion, in favor of the ion. That is, when one 

 gram ion of silver changes into one gram atom in the same space 

 96, 540 X i . 163 Joules of energy are set free, or since each monovalent 

 ion carries 9.65Xio~ 20 coulombs of electricity, when one silver ion 

 changes into a silver atom at any concentration, 9.65 X io~ 20 X i . 163 

 Joules of energy are set free. 



It will be seen, by comparing Tables i and 2, that the true values 

 of the ionic potential calculated in this way do not in most instances 

 differ greatly from the values of the solution tension in normal ionic 

 solutions. The heavy metals have, as a rule, an ionic potential about 

 0.070.1 volts different from the solution tension in normal ionic 

 solutions.* 



* I have not calculated the ionic potentials of Cl. Br, and I, but have used instead the figures for solu- 

 tion tension in normal ionic solution. It is also impossible to calculate the ionic potentials of Ca, Li, Ba, 

 Na, and K. 



