334 MR. W. C. D. WHETHAM ON THE IONIZATION OF 



August 7, 1899. Volume of Cell. 



Weight of water run into cell from the large filling machine. . 23G'lf> 



Weight withdrawn at '4 16 '56 



Weight of water in cell 219'60 



Weight added from small filling machine 8 '14 



Weight withdrawn at 0' 5 !..,... 8'11 



Weight of water in cell 219'63 



[Weight added . i . ' 9'27 



Weight withdrawn at 0'5 . . ' . 8 '85 



(Full pressure of water pump) 



Weight of water in cell . V 220'05] 



Weight added . ;-..-.. -..-. ....", -;':-y -. ..:;:., u . 9'47 



Weight withdrawn at -6 . . -..- .i .-'.. .... 9'93 



Weight of water in cell . .'... . .L-... . . . 219'59 



Mean value ... . . . . . 219'61 



Another example, August 20, 1899. 

 Weight of water in cell : 219'25, 219'36, and 219'34. Mean = 219'32 



Thus the greatest error introduced into the value for the concentration of the 

 solutions by this part of the operations is about one in two thousand. 



Constancy of Resistance of the Solvent. During the early stages of the work it 

 was found impossible to keep the resistance of the water in the cell at a constant 

 value for any length of time, rapid increase in conductivity always appearing. This 

 change occasioned great difficulties, in fact months were given to the investigation of 

 its cause and cure. It seemed to be due to the gradual absorption of traces of 

 impurity (such as carbonic acid, &c.) from the atmosphere, for whenever a fresh 

 quantity of air found its way into the apparatus, the resistance fell for some time, 

 the fall being quicker when the screw was kept in continual motion. It was therefore 

 found advisable to fill the cell for some time before using it, for while the contents 

 were cooling, air was of course being drawn in, and, until all the impurities in that 

 volume of air had been absorbed, no constancy of resistance could be obtained. 

 Again, when the contents were levelled, water was drawn out, and. therefore, air 

 entered to replace it, and this also caused variation for some little time. This leakage 

 of air also occurred when salt had been added, chiefly at the moments when stock 

 solution was being introduced into the cell. Its effect was to change the form of the 

 ionization curves for dilute solutions, the impurities as they gradually accumulated 



