at the Contact of Mutually Reacting Liquids. 533 



were saturated with the liquids to be tested, and contact 

 between them was made either by a strip of the same paper, 

 across which the two liquids soaked till they met, or by an 

 arrangement consisting of two small funnels with fine drawn- 

 out ends like those shown in fig. 2. These contained the two 

 solutions connected by strips of filter-paper with their re- 

 spective cylinders. As the liquids flowed out from the fine 

 ends of the funnels they came in contact with continuously 

 fresh surfaces, thus providing a continuous renovation of the 

 surface of contact and preventing any possible permanent 

 modification. I am not able to say, however, that this gives 

 a result sensibly different from the simple paper connexion. 



The water-dropping testing funnel was provided with a 

 stopcock, and its nozzle had three fine jets. By means of an 

 insulated adjustable support this nozzle could be placed at will 

 in the interior of either paper cylinder. The water in it 

 was connected to the electrometer-key by an immersed 

 platinum plate. To make a test, the two cylinders A, B were 

 prepared and connected as described above, and an earthed 

 platinum strip w r as placed in contact with A. The funnel 

 jet was then allowed to discharge in the interior of the 

 cylinder A, and the difference of potential between its platinum 

 connexion and that of A measured by deflexion on the Thomson 

 electrometer. This deflexion of course includes measurement 

 of any contact difference at platinum-liquid connexions. The 

 funnel jet was then changed to B, and the deflexion again 

 noted. The difference of these deflexions was taken as the 

 contact difference of potential A/B of the two liquids. 



2. The first few experiments made with this apparatus were 

 based on the assumption that, as the oxidation of a metal by 

 an electrolyte electrifies the metal negatively, the raising of 

 a salt from a lower to a higher oxide or chloride might have 

 the same effect. Strong solutions were used, but the exact 

 strength was not ascertained. 



Table I. 





Positive. 



Negative. 



E.M.F. 



1. 



2. 



3. 

 4. 

 5. 

 6. 



7. 

 8. 



Ferrous Sulphate 



j; 



Arsen ious Acid 



Stannous Chloride ... 

 Ferric Chloride 



Hydrogen Peroxide 



•07, -07 volt, 

 •06, -OS „ 

 •0i „ 

 •07 .. 

 •10, 12 ., 

 03 „ 

 •07 „ 

 •20 „ 





Potassium Permanganate. .. 

 Water + dissolved Oxygen . 



Potassium Bichromate 



Iodine and Water 



Mercuric Chloride 



Sulphurous Acid 





Hydrogen Sulphide 







