180 Medway — Material and Shape of the Rotating Cathode. 



Art. XXIII. — The Material and Shape of the Rotating 

 Cathode ; by H. E. Medway. 



[Contributions from the Kent Chemical Laboratory of Tale University — CXXZ.] 



In a previous article from this laboratory* a method has 

 been described for the rapid, electrolytic precipitation of 

 metals upon a rotating platinum crucible made to serve as a 

 cathode. In the present paper is given the record of experi- 

 ments with other and cheaper metals, used in place of the 

 more expensive platinum, as well as cathodes in the form of 

 discs. 



Experiments were made with a silver crucible of 50 cm3 

 capacity, carefully cleaned, dried at 100° C, weighed and 

 adjusted to the rubber stopper which serves to hold the cru- 

 cible and press against its inner wall two platinum strips which 

 make the electrical connection. 



Into the electrolytic cell was put an acidulated solution of 

 copper sulphate, standardized by deposition of copper upon the 

 rotating crucible of platinum. 





Deposition upon Silver. 







. Copper 



Copper 











taken. 



found. 



Error. 



Current. 



N. D. 



Time 



grm. 



grm. 



grm. 



Amp. 



100. 



min. 



(1) 0-1088 



0*1086 



— 0t)002 



2- 



6-6 



15 



(2) 0*1088 



0-1090 



+ 0-0002 



2- 



6-6 



15 



(3) 0-1088 



0-1084 



— 00004 



1-5 



5- 



15 



(4) 0-1088 



0-1085 



— 00003 



2- 



6-6 



15 



(5) 0-1088 



0-1080 



— 0-0008 



2- 



6-6 



15 



(6) 0-1041 



0-1041 



+ 0-0000 



2- 



6-6 



15 



(7) 0-1041 



0-1046 



+ 0-0005 



2' 



6-6 



15 



(8) 0-1041 



0-1039 



— 0-0002 



2- 



66 



15 



The results of these experiments would seem to indicate 

 that the use of a silver crucible leaves little to be desired so 

 far as accuracy is concerned. 



To remove the copper from the crucible, the deposit was 

 rubbed off as much as possible and the rest dissolved in a 

 strong boiling solution of hydrochloric acid, and this was 

 accomplished with but trifling loss of silver, as is shown in the 

 statement below : 



Weight of crucible before treatment _. 36*0089 



Weight of crucible after treatment 36-0062 



Loss of silver 0-0027 



* Gooch and Medway : This Journal, xv, 320, 1903. 



II. 



36-0062 



36-0041 



0-0021 



