572 MR. F. E. SMITH, MR. T. MATHER, AND DR. T. M. LOWKY 



from anode to kathode should not be large enough to allow of a decomposition of 

 water. We have made experiments to test this, and give the results obtained when 

 the potential difference was varied from 0'03 volt to 30 volts. The effect of using 

 a platinum anode is discussed in Part II., p. 588. 



Effect of Potential Difference between Anode and Kathode (56 and 566). 



When a syphon form of voltameter and a Rayleigh form were placed in series and 

 a current of 1 - 02 ampere passed through them, the drop in potential on the syphon 

 form (small syphon) was of the order of 30 volts and on the Rayleigh form about 1 volt. 

 It has already been shown that the mass of silver deposited on these occasions is the same. 

 Comparison observations were also made with a very high resistance Rayleigh volta- 

 meter and one of the usual type. The voltameters were placed in series and the 

 kathode bowls of each contained 350 cub. centims. of a 15 per cent, solution of silver 

 nitrate. The high -resistance voltameter was one in which the filter paper was 

 enclosed in a glass funnel perforated with small holes, and the funnel was enclosed in 

 a second similarly perforated. With a current of 0'03 ampere the difference of 

 potential on the high-resistance voltameter was 3'0 volts, and that on the usual form 

 was 0'03 volt. The deposits were very loose and markedly striated. The mass of 

 silver deposited in 50 hours in the usual form was 7*10382 grammes (56a), and in 

 the high-resistance form 7 '104 11 grammes (566). These results are interpreted as 

 indicating that in all ordinary cases the potential difference produces no disturbing 

 effect. 



Variable Concentration of Electrolyte. 



The extreme range in the concentration of the electrolyte has been from 1*5 parts 

 to 50 parts of silver nitrate in 100 parts of the solution, the intermediate values being 

 5, 10, and 15 parts in the same quantity of solution. The chief difference in the 

 deposits was that of texture, the solutions of higher concentration giving less adherent 

 and more striated deposits than the weak solutions when the current employed was 

 between O'l and TO ampere, but from I'O ampere upwards the striae were faint even 

 for the concentrated solutions. When the 1'5 per cent, solution was used, only 

 3 '3 grammes of silver were present in the electrolyte, and the degree of the electrolysis 

 at the end of this experiment was therefore 7'l/3'3 = 2'15. 



The masses of silver in milligrammes per coulomb recorded as deposited from the 

 various solutions are as follows : 



1-5 per cent, solution = 1-11823 (646). 



5-0 = ri!825 8 (40a, 40c). 



10-0 = T11827 (33a, 6, c). 



15-0 = 1-11827 (large number of observations). 



50-0 - 1-11827 (306). 



