654 Dr. S. R. Milner on the 



the ionic mobility of silver at infinite dilution (i. e., that part 

 of the molecular conductivity of a silver salt which depends 

 on the silver ion only) the value 55*7 at 18° C. This is 

 equivalent to 



U = 5'77 x 10" 12 cm. per second for a slope of potential 

 of one electromagnetic unit per cm. 



With this value 



! =^=-03072, 



VtoKTU 



and consequently 



V = -0578 log 10 \l+'°*~ 12 $S r CSt=t r \ 



where the concentration must be expressed in gramme- 

 molecules per c.c, the current in E.M. units, and the time in 

 seconds. When the concentration is expressed in gramme- 

 molecules per litre, the current in amperes, and the time in 

 minutes, the factor '03072 must be replaced by 



•03072 x 1000 x ^ x •tJO, r 23"80, 



and 



V = -0578 log 10 { 1+ 2 ^° Z8 r C ^t-t r \ volts. (24) 



Since the absolute temperature varies *34 per cent, per 

 degree at 18° C, and the ionic velocity of silver varies 

 approximately 2 per cent, per degree, the factor "0578 is 

 subject to a variation of -f '34 per cent., and the factor 23'8 

 to a variation of —1*17 per cent, for each degree above 

 18° C. 



Results ivith SilverSitrate Cells. 



In making the experiments a cell similar to that shown in 

 fig. 1 was used. The beakers were suspended in a large 

 water-bath which stood on a slate shelf free from the floor. 

 The bath, although its temperature varied when measured 

 over long periods,.. showed no appreciable variation in the 

 period of a few hours required for an experiment ; and con- 

 vection effects are likely to be more completely eliminated 

 in this way than when a thermostat is used, in which case 

 slight but quick fluctuations of temperature occur. The 

 electrodes were of fine silver containing 99*8 per cent, of the 

 metal, and had shown themselves satisfactory in previous 

 concentration-cell experiments. The anode A was cast in 

 the form of a small button and turned down so as to exactly 

 fit the surrounding glass tube, into which it was cemented 



