194 Dr. C. R. A. Wright and Mr. C. Thompson. [May 3, 



E.M.F. of Cells set up with Amalgamated Zinc or Bright Silver and 

 Ammoniacal Solutions, #NH 3 ,2/NH 4 Cl,100H 2 O. 

 x = 2-6. 





Zinc. 



Silver. 



$ = 0, 



y = o-8. 



y = 5. 



y = o. 



y = o-8. 





Platinum sponge 



1-430 



1-482 



1-499 



0-085 



212 



0-239 



Gold sponge . . . 



1-420 



1-422 



1-442 



0-075 



152 



0-182 



Silver sponge. . . 



1 -380 





1-391 



0-035 





131 



Platinum foil . . 



1 -370 



1-367 



1-370 



0-025 



0-097 



0-110 





1-315 



1-334 



1-365 





0-064 



0-105 



In general the E.M.F. rises with increased solution-strength, 

 platinum foil being exceptional when opposed to zinc, the E.M.F. here 

 being practically constant. 



The various tables above stated clearly show that the order of 

 magnitude of the E.M.F. generated when a given kind of aeration 

 plate is opposed to a given oxidisable metal, depends on the nature, 

 and to some extent also on the strength, of the solution used as electro- 

 lytic fluid. The following table indicates the relative order in which 

 various plates come in solutions of caustic soda, sulphuric acid, and 

 ammoniacal liquors respectively : — 



Caustic Soda. 



Silver sponge (acetate). 



Palladium sponge. 



Silver sponge (chloride) . 

 J Platinum sponge. 

 \ Platinum black. 

 J PaUadhmi foil. 

 \ G-old sponge, 

 f G-raphite. 

 <{ Gold foil and leaf. 

 j_ Platinum foil and leaf. 



Silver foil and leaf. 



Carbon. 



Sulphuric Acid. 



Platinum black. 

 Platinum sponge. 

 Palladium sponge. 

 Gold sponge. 

 fPlatinum foil and leaf. 

 Palladium foil. 

 Gold foil and. leaf. 

 Graphite. 

 (^Carbon. 

 Silver sponge. 

 Silver foil and leaf. 



Ammoniacal Fluids. 



Platinum sponge. 



Gold sponge, 

 f Silver sponge. . 

 \ Carbon. 

 J* Palladium foil. 

 \ Platinum foil. 



G-raphite.* 

 f Gold foil. 

 \ Silver foil. 



In all cases a metal in the state of sponge gives a higher value than 

 when in the state of polished foil or thin leaf. 



Comparison between the E.M.F. generated in Aeration Plate Cells and 

 the Chemical Action going on therein. 



In the case of cjlls with caustic soda as electrolytic fluid, the nett 

 chemical change is the oxidation of the oxidisable metal to form 



