Platinum Electrodes of Light Weight. 109 



Electrolysis of Nickel Ammonium Sulphate* 









Initial 









Nickel 



Nickel 





CUl 



•rent 









taken 



found 



Error 



^- 



j , 



Approx. 



Time 



grm. 



grm. 



grm. 



amp. 



volt. 



N. 



JJ.ioo 



min. 





Platinized test-tube, 



used as 



cathode. 









0-0746 



0-0744 



— 0-0002 



0-8 



7-5 





4 



40 



0-0746 



0-0743 



— 0-0003 



1-2 







6 



35 



0-0744 



0-0744 



0-0000 



1-2 







6 



50 



0-0743 



0-0739 



— 0-0004 



1 



7-5 





5 



30 



0-0743 



0-0742 



—o-oooi 



0-6 



7-5 





3 



40 



Platinized thistle-tube, used as cathode. 



0-0742 00741 —0-0001 15 5 30 



* With addition of 1 grm. of (NH^SOj and 25 om3 of concentrated ammonia. 



These results show that the inexpensive apparatus described 

 is capable of yielding good results. The chief difficulty lies in 

 the tendency of the film to disintegrate when the deposited 

 metal is subsequently dissolved off the electrode, so that after a 

 few successive determinations the film needs to be renewed. 

 There is, moreover, some tendency to the disengagement of 

 particles during the process of electrolysis, and this no doubt 

 accounts in great measure for the negative errors noted above. 

 It was shown in other experiments that this loss of cathode 

 material is likely to be greater, possibly amounting to as much 

 as 2 to 3 mm , when the films are too much reinforced by the 

 application of several successive layers of the plating 'mixture. 

 The weight of platinum in the films used in the experiments 

 described above did not exceed 0-2 grm. spread upon a surface 

 of approximately 20 cm2 . The entire weight of platinum in the 

 film and connecting wire of the cathode amounted to about 

 - 7 grm. It is probable that the slight losses due to the cathode 

 disintegration in the course of an analysis might be reduced by 

 the use of the filtering device to be presently described ; but 

 the use of small electrodes and a weighable cell proved to be 

 so much more convenient that the experiments with the 

 platinized glass were carried no further. 



Electrolysis with Small Electrodes in a Weighable Cell. 



If the current directly employed in electrolytic analysis is 

 high, as is inevitable in rapid processes in which small electrode 

 surfaces are employed, the deposits of metal lack compactness 

 and are likely to be disengaged from the electrode. The 

 apparatus to be described was devised to retain and gather the 

 detached material so that it may be weighed with the remain- 

 der of the cathode deposit. The device, shown in figure 2, 



