190 Mr. J. Daniel on the Polarization upon a 



make the current as nearly as possible the same with partition 

 in and partition out. This could not be done exactly, but 

 was corrected by interpolation. We shall be mainly con- 

 cerned with the polarization on the partition ; and we see 

 from (A) that this polarization, expressed in volts, is the 

 simple product of current- strength in amperes, and the change 

 of resistance necessary to keep the current the same when 

 the partition is added that it was with partition open. 



The same box of resistance was used for all purposes — in 

 determining the u figure of merit " of the galvanometer, the 

 resistance of the voltameter, and as rheostat to regulate the 

 main and branch currents ; hence we are not concerned with 

 the question as to whether the units are true ohms, as it does 

 not affect our results. 



Solutions used as Electrolytes. 



With the old voltameter relative values have been obtained 

 for 30 per cent. H 2 S0 4 , 5 per cent. H 2 S0 4 , and very dilute 

 H 2 S0 4 , such as to give voltameter resistances of 20, 60, and 

 100 ohms, about. With the new voltameter, quantitative 

 measurements have been made with 



30 per cent. H 2 S0 4 ; sp. gr. =1'22 ; v= 1*1 ohms. 

 „ „ CuS0 4 ; „ =1-12; v = 24-5 „ 

 „ „ NaOl; „ =1-12; v= 5'5 „ 



Also some observations with 



3 per cent. H 2 S0 4 ; sp. gr. =1*2 ; 

 „ „ KOH; „ =1-11; 



and very dilute sulphuric acid. 



As partitions in the voltameter, platinum, gold, silver, and 

 aluminium have been used, such as are described below. The 

 thickness of the thick plates was measured with a micrometer- 

 gauge ; that of the thin plates was calculated from their size, 

 weight, and specific gravity. The plates marked S, & W. 

 were from Sy and Wagner, of Berlin, and are supposed to be 

 quite pure. Those marked M. are from Miiller, of Dresden, 

 and are, some pure, as indicated, others of the quality of the 

 finest gold-leaf, i. e. 0*925 pure. It will be convenient in the 

 Tables to refer to these partitions by the numbers, and the 

 following description will suffice once for all. 



