ON THE SILVER VOLTAMET1!! 581 



I! vi i .IK. ii li;is hfcii employed on most occasiona We are unaware of the exact 

 conditions of the experiments, but it will be seen that the differences between the 

 values and the mean value are not appreciably greater than the probable errors of 

 many of the current determinations. It must be remembered that in the very early 

 observations great precision was not claimed. 



PATTERSON and GUTHE used a type of voltameter in which the electrolyte was 

 saturated with silver oxide, and their result is not therefore comparable with the 

 others. (JiTHK and VAN DlJK employed the Richards and the Kuyleigb forms; the 

 values given in Table X. are those obtained by them for the Rayleigh pattern. 



Conclusions. 



(1) The Rayleigh, the Richards, the Syphon, the Pot-Syphon-Bowl, the Syphon- 

 Pot-Bowl, and the Elevated Kathode forms of voltameter give identical values within 

 1 or 2 parts in 100,000 for the electrochemical equivalent of silver, subject to easily 

 attained conditions with respect to the size of the voltameter and the purity of the 

 electrolyte. (The purity of the electrolyte is dealt with in Part II.) 



(2) The mass of silver deposited is independent of the pressure to which the 

 voltameter is subjected, and also independent of the temperature, except that at high 

 temperatures the filter paper of the Rayleigh form may interact with the silver 

 nitrate solution, and give rise to a very slightly abnormal value for the electrochemical 

 equivalent of silver. 



(3) The current through the Rayleigh form ot voltameter* may vary from 

 0'5 ampere to. 8 amperes, and possibly beyond these limits without producing any 

 appreciable disturbing effect. 



(4) The electrochemical equivalent of silver is 



1'11827 milligrammes of silver per coulomb (10" 1 C.G.S.). 

 This value is subject to a probable error of about 0'002 per cent. 



PART II. 



The Chemistry of the Silver Voltameter ; 

 by F. E. SMITH, A.R.C.Sc., and T. M. LOWRY, D.Sc. 



A. Preparation of Pure Silver Nitrate. 



In the earlier experiments (1 to 13) on the electrochemical equivalent of silver con- 

 siderable difficulty was experienced in obtaining concordant figures when different 

 samples of silver nitrate were electrolysed under apparently identical conditions. Many 



* The size of the voltameter is assumed to be the same as that described in this communication. 



