240 J. Olsen — Investigation into the Existence of 



J. H. Pratt* shows that no current passes through a capil- 

 lary electrometer below 1*22 volts. If no current can pass 

 through a Lippmann electrometer before about the electrolytic 

 limit of decomposition is reached, then this instrument is not a 

 good one for this experiment. 



In order further to test the capillary electrometer when 

 connected for some time to voltages below 1-22, I made an 

 instrument as follows: 



A glass tube about 15""" in length was drawn to a capillary 

 at about S'^'" from one end. Into this shorter portion a platinum 

 wire was fused. The tube was then filled with mercury and 

 dilute sulphuric acid and inverted into a beaker containing 

 dilute sulphuric acid and mercury. A cork was put on the 

 upper end, and by releasing this a little the boundary between 

 the mercury and sulphuric acid could be brought into the 

 capillary. A space was left above the mercury so that it could 

 recede when connected up to a Daniell. A platinum wire 

 connected with the mercury in the beaker. 



In this form the instrument, so far as its effective action is 

 concerned, is exactly the same as that used by Ostwald and 

 ^Nernst. 



It w^as connected up to a Daniell of about 1-05 volts for 

 hydrogen polarization and watched every few minutes for five 

 hours, but no bubbles of gas were observed. It was afterwards 

 connected up at the same voltage for eight hours with the 

 same result. 



Incidentally it may be stated that it was found that, if the 

 tube was sealed at the upper end and entirely filled with mer- 

 cury so there was no chance for it to recede, bubbles were 

 formed in a few minutes, first at 1*05 and later with a new 

 tube and new mercury at about '88 volts. 



In 1888 Ostwaldf cites the following as a proof of the 

 existence of free ions in solutions, but does not perform the 

 experiment. 



Let two vessels, A and B, be filled, for example, with a solu- 

 tion of potassium chloride, insulated and connected by a siphon 

 filled with the same liquid. Now let a negatively charged 

 body, K, be brought near to A ; it will act inductively upon the 

 system. A will become positive and B negative. If now the 

 siphon be removed and then the body K, A will remain posi- 

 tive and B negative. To discharge A we can connect it with 

 the earth, and the potassium ions, which are positive, will give 

 up their charge and become atoms. These would act upon the 

 water, forming potassium hydroxide, and hydrogen, which 

 would escape from the solution as a gas. 



*Tliis Journal, 1888 f Zeitsclir. Phys. Chem., ii, 1888. 



