1894.] with a Fused Electrolyte and a Gaseous Depolarizer. 63 



pole. The electrolyte was fused PbCl 2 . The whole was heated in a 

 gas furnace. When the electrolyte was fused, the chlorine was passed 

 rapidly through, so that it issued from under the porcelain crucible. 

 The E.M.F. was then between 0'94 and 0'96 volt., and never rose 

 higher than O98 volt. The lower E.M.F. was evidently due to the 

 fact that part of the surface of the carbon pole was not subject to the 

 action of the chlorine, but remained polarised by deposition of lead. 

 The behaviour was much like that of a constant cell with an E.M.F. 

 of between 0'94 and 0'96 volt. The method of observation was to 

 alter the exterior resistance and then read the current and P.D., then 

 break the circuit and read the E.M.F. 



Calculated internal resistance. 



oi 



1 



I 



From these observations it will be seen that the internal resistance 

 was calculated, col. 3, in order to find whether polarisation is greatest 

 when a small or large current is taken from the cell. From the 

 results it is apparent that the internal resistance, and at the same 

 time the polarisation, decrease when the current increases. This kind 

 of cell, therefore, differs from those in which aqueous electrolytes are 

 sed, inasmuch as the polarisation decreases with increased electrical 

 'utput. The observations of P.D. and E.M.F. were taken almost 

 imultaneously, and the variation of resistance as the gas bubbles 

 passed out was thus avoided. As the internal resistance was very 

 small the whole time, and remained almost constant during a varia- 

 tion of the current from 1'26 to 2'5 amperes, it may be said to be a 

 constant battery, with an E.M.F. lower than the theoretical value. 

 The reason of this lower E.M.F. is probably due to some part of the 

 large carbon plate being covered with reduced lead, thus forming an 

 opposing couple of smaller capacity and lower resistance than the 

 primary elements, its effect being to reduce the main current. The 

 E.M.F. of this opposing couple is of necessity the same as that of the 

 main current, but, owing to its lower internal resistance, its P.D. is 

 less ; if it were not so, the cell would yield no appreciable current. 

 This reasoning explains why the results obtained with small cells 

 were better than those obtained with large ones. 



Besides the experiments mentioned, trials have been made, with 



