﻿406 Sir W. Ramsay and Dr. Spencer on Chemical and 



SJTo show that the effect of altering the relative positions of 

 the light and the electroscope made only a relative change in 

 the rate of discharge, measurements were made with tin 

 and the standard at two distances; the relation between the 

 discharge at the two distances was found to be the same for 

 both plates, as seen in Table IV. 



Table IV. 

 Negative charge 800 volts. 



Plate. 



Distnnce d' 

 66 cms. 



Distance d" 

 26 cms. 



Ratio d'/d". 



Tin 



37 sees. 

 29 sees. 



6*2 sees. 

 4*8 sees. 



5-961 



U-oo 



6-04 J 



Copper amalgam ... 



All rates of discharge in these and subsequent experiments 

 are for 10 scale-divisions. In all experiments the initial 

 potential of the electroscope was 800 volts, and the final 

 potential, i. e. after the leaf had moved over 10 scale- divisions, 

 was 680 volts ; this potential was found to be well above that 

 required to ensure a saturation current in the case of the 

 most rapid discharge. 



Table V. (p. 408) gives the relative rates of discharge for a 

 series of elements. Each element, when enough was obtain- 

 able, was fashioned into a plate 9 cms. long and 6*1 cms. 

 wide, and compared with a plate of copper amalgam of the 

 same size ; moreover, each measurement was corrected for the 

 natural leak of the electroscope. The value of the natural 

 leak was obtained in every case by making blank experiments 

 before and after the measurement of each plate. Where it 

 was impossible to obtain plates of the above dimensions, 

 smaller plates were compared with smaller standards. The 

 ratio between the rates of discharge of the large and small 

 standards was also determined, and from these values the 

 figures obtained were brought into a uniform relative series. 

 In the case of mercury a special arrangement was made as 

 illustrated in fig. 4. The electroscope consisted as before of 

 a metal box fitted with the necessary earth- connected guard- 

 rings. The arrangement of the leaves was as indicated in 

 the diagram, the charging disk C was insulated in the same 

 manner as the leaves by a sulphur plug. The mercury was 

 placed in an insulating dish D of sulphur, which also served 

 as an insulating support for the standard plate. Series A 



