548 



MR. F. E. SMITH, MR. T. MATHER, AND DR. T. M. LOWRY 



For convenience this communication is divided into two parts. In some of the 

 very early experiments it was ftmnd that the mass of the deposit was dependent on 

 the mode of preparation of the silver nitrate. A considerable quantity of the 

 crystallised salt was necessary for the observations, and for economy and experience 

 the salt was recovered from the used solutions by recrystallising. The first products 

 gave very remarkable results, both as regards the deposited mass and its appearance, 

 but on further purification the normal salt giving normal deposits was obtained. The 

 abnormal results were found to be due to impurities hitherto unsuspected, and which 

 are hot usually contained in the salt purchased as pure in the ordinary way ; they 

 appear to arise in the manipulation of the solution, the fusion of the salt, and its long 

 exposure to the air. These impure solutions are dealt with in the second part of this 

 communication. In the measurements discussed in the first part the pure salt only 

 was used. 



PAKT I. 



A Comparison of Various Forms of Silver Voltameters, by F. E. SMITH, A.R.C.Sc. ; 



and a Determination of the Electrochemical Equivalent of Silver, 



by F. E. SMITH, A.R.C.Sc., and T. MATHER, F.R.S. 



Description of the Voltameters. 



Eleven platinum vessels and two silver ones have been used for the kathodes of the 

 voltameters. The dimensions, approximate masses, capacities, &c., of these vessels 

 are given in the following table. We are indebted to Messrs. Johnson, Matthey 

 and Co. for the loan of the vessels A, B, C, D, L, and M. 



