Section 36. Change in Conductance-capacity. 



79 



introducing weighed portions of mercury into the cup and measuring by 

 a cathetometer the height of its surface above the electrode and below 

 the top of the cup. The heights of the mercury in the cup were plotted 

 against the weights of mercury, the points being found to lie on a straight 

 line; and by means of these plots, the effective height of the cup in the 

 succeeding experiments was derived from the weight of mercury intro- 

 duced. The relative conductance at various heights was then determined 

 by measuring that of a 0.01 normal sodium chloride solution at 18 in the 

 apparatus, which was made up of the three electrode cups in succession 

 and one of the brass cylinders, successive portions of mercury being added. 

 The effective heights of the cup were first plotted against the conduct- 

 ances. The diameters of the three cups were then plotted against the 

 conductances obtained for various definite heights from the first plot. 

 From these plots, the ratio of the fractional change in conductance (8l/l) 

 to that in height (8h/h) for a given diameter or to that in diameter 

 (Sd/d) for a given height could be found. The results so derived for a 

 series of heights and diameters expressed in centimeters are given in table 



Sr /l 

 15. The columns headed 1 show the values of the ratio r^rr and those 



Sh/h 



headed ir, the values of the ratio 



8l/l 

 8d/d 



Table 15. Change in conductance-capacity with the dimensions of the electrode cup. 



The apparatus for determining the variation of the conductance when 

 no cup was used was made up as follows. The top of the main body of 

 the bomb was covered with a brass disk. Through the center of this disk 

 was inserted a hollow rod of vulcanite of the length and diameter of the 

 quartz cylinder supporting the lower electrode in the bomb itself. Through 

 this vulcanite tube a brass rod was inserted, which could be forced down 

 successively so as to produce an electrode of varying length. The con- 



