RICHARDS AND HEIMROD. THE IMPROVED VOLTAMETER. 431 



of the usual disturbauce. But in view of the fact that even a deficit of 

 0.14 per cent can be obtained, not much importance can be attached to 

 these results, since it is impossible to say how much is due to the oxidiz* 

 ing action, how much to the disturbing influence capable of causing an 

 actual deficiency. 



These indirect methods of determining the presence of a complex yield- 

 ing metallic silver being somewhat unsatisfactory, recourse was had to a 

 more direct method. It seemed highly probable tliat the anode solution 

 ought to be able to deposit silver without the help of the galvanic current. 

 In order to show this, a porous cup voltameter was set up in the usual 

 manner, except that the anode was closely wrapped in filter paper to 

 retain the fine crystal powder which always separates from it. A current 

 of 0.25 ampere was sent through the voltameter, and every ten minutes 

 a portion of the clear anode solution was taken from the bottom of the 

 porous cup by means of a small pipette, and quickly transferred to a 

 small weighed platinum crucible. 



The crucible had been previously coated with silver in order to estab- 

 lish equilibrium more quickly in case a compound existed in the solution 

 which tended to deposit silver. 



After one hour's standing, the liquid was removed and the crucible was 

 washed and dried, as a deposit from electrolysis would have been. The 

 increase in weight of the crucible must represent the deposit from the 

 anode solution. 



TABLE X. 

 Gain in Weight of Silver in Contact with Anode Solution. 



No. Increase in Weight. 



Milligram 



33 0.35 



Si 0.08 



35 0.25 



36 0.63 



Mean . . 0.33 



The weight of the same crucible did not change perceptibly when 

 allowed to remain in contact with a solution of silver nitrate of like con- 

 centration, through which no current had previously been passed. The 

 above increase in weight shows beyond a doubt, therefore, that the anode 

 solution is capable of depositing on a silver surface either silver or 

 some compound of this metal which must have been formed at the anode. 



