294 



Mr. J. Daniel on the Polarization upon a 



through this partition, developing profuse gas, and it was 

 thought probable that the palladium was being dissolved by 

 the 30 per cent. H 2 S0 4 under the action of the current. 

 Accordingly a test of the solution was made for palladium 

 by adding ammonia till alkaline, and then adding ammonium 

 sulphide, which gave no indication of the presence of pal- 

 ladium. 



It has been observed that Pt is perfectly constant, showing 

 the same " critical current " as often as tested. Gold is 

 oxidized the first time the " critical current " is attained, and 

 its value decreases on repeating the test (with the same 

 specimen). 



Efforts were made to test the critical currents for four 

 thicknesses of gold from 0*0004 to 0'0018 millim., in am- 

 monium nitrate, hoping that this would not oxidize the gold ; 

 but the partitions were oxidized by currents strong enough to 

 develop gas. 



Table I. 



A 17 per cent, solution of Cu80 4 with a Cu anode, sepa- 

 rated by a gold-leaf partition from a 30 per cent, solution 

 of H 2 S0 4 with Pt kathode. 



Time, in 

 minutes. 



30 



Current, in 

 amperes. 



0-175 



Cu deposited on 

 kathode, in grms. 



0-003 



Ratio of Cu to 

 current. 



3 per cent. 



Allowed this voltameter to stand from Saturday till Monday, and 

 then made the following determinations in rapid succession: — 



33 



40 

 40 

 45 



0-205 

 0-206 

 0127 

 054 



0765 

 00920 

 00700 

 00380 



38 per cent. 

 57 „ 

 70 „ 

 80 



Set up two new voltameters, fll and #2, and connected them in 

 series. The gold-leaf partition in #2 broke before the current was 

 closed. Then the following values were found : — 



30 



0-132 



#1. 

 0-002 



Then after standing some hours, 



30 0147 I 0027 



32 0-152 0-0453 



«2. 



0-0766 



0-085 

 0095 



*1. #2. 



2-6 p. c. 99 p. c. 



31 „ 

 47-6 „ 



99 

 100 



Fresh solutions. Partition of fll is single gold-leaf; of (2 is double 

 gold-leaf. Then : — 



65 



0-035 



0-0022 0-0026 



5 p. c. 57 p. c. 



