ON THE SILVER VOLTAMETER 



577 



liquid consisted of about 30 cub. centims. of a 20 per cent, solution, and at times 

 nearly 3 grammes of silver were deposited, the concentration being thus reduced to 

 about 4'3 per cent. Professor VAN DIJK. observed little or no striae in the Richards 

 form, but marked striae in the Rayleigh form. 



In the Rayleighr form the process of intermixing of the anode and kathode liquids 

 is considerably accelerated by their ascent and descent respectively. We have made 

 observations on the currents of liquid thus produced and find that they may be 

 approximately represented by fig. 11. The electrolyte which is above the horizontal 



Fig. 11. 



plane containing the sheet of silver which forms the anode is certainly of lower 

 concentration than that below this plane when electrolysis has proceeded for a short 

 time. It therefore appears that the kathode film may be stable in the upper portion 

 of the electrolyte when it is unstable in the lower portion. In other words, it should 

 be possible to produce striae at the base and bend of the bowl when the upper portion 

 of the deposit presents a matt surface (see fig. 9). Probably this has been observed by 

 other workers besides ourselves, but we have found no reference to the phenomenon. 

 Our own deposits at low current densities were often markedly striated at the bend of 

 the bowl and gradually merged into the matt surface which existed above the point A. 

 The portion B of the electrolyte, which is partly enclosed by the curved surface of the 

 liquid, is in a most unfavourable position for the renewal of its original concentration, 

 and it is probably of smaller density than any other part of the solution. Because of 

 tliis the conductivity is small, and an appreciable E.M.F. acts from B towards the 

 main body of the electrolyte ; in consequence, the quantity of silver precipitated by 

 the passage of electricity through B is very small. In most of our experiments we 

 have closely observed the deposit and the electrolyte, and in about six instances have 

 found a distinct gap between the line of contact of electrolyte and platinum and the 

 edge of the deposited silver. In these cases a few crystals of silver were sometimes 

 VOL. ccvu. A. 4 E 



