56 Medway — Farther Work with the totaling Cathode. 



Akt. IX. — Further Work %oith the Rotating Cathode; by 

 H. E. Medway. 



[Contributions from the Kent Chemical Laboratory of Yale University. — 



CXXVIII.J 



It has been shown in a previous article* that metals may be 

 precipitated electrolytically, with great economy of time and 

 with much exactness, by the use of a rapidly rotating cathode. 

 The apparatus employed consists of a platinum crucible fastened 

 to the vertical shaft of a small electric motor and dipping into 

 the solution to be electrolyzed. A current from a series of 

 storage batteries is passed through the solution between a 

 platinum anode and the crucible, which serves as the cathode, 

 while in rapid rotation ; it being found that under these con- 

 ditions a high density of current may be used with a consequent 

 shortening of time over that required for complete deposition 

 with a stationary cathode. 



In the article referred to, attention is called to the rapid 

 determination of copper, silver and nickel electrolytically. It 

 is the purpose of the present article to give results, obtained in 

 the same way, in a study of the conditions adapted to the use 

 of the apparatus upon solutions in common use in the ordinary 

 process of electrolysis between stationary electrodes, and in some 

 cases studied by Exnerf with reference to the application of 

 the stirring anode and ordinary cathode to similar rapid pre- 

 cipitations. 



Cadmium. 



Cadmium sulphate, approximately 0'2 grm., was dissolved in 

 50 cm 3 of water, 10 drops of dilute sulphuric acid added to give 

 conductivity and the solution was electrolyzed, while the cru- 

 cible, serving as the cathode, was rotating at a rate of 650-700 

 revolutions a minute. It was noticed that a perceptible solvent 

 action of the acid takes place upon the deposit of cadmium in 

 the short time necessarily taken to remove the crucible from 

 the liquid. Therefore, in order to avoid siphoning, dilute 

 ammonia was added drop by drop after the metal had been 

 all deposited and while the current still passed, until the solu- 

 tion was faintly alkaline. 



That this procedure proves satisfactory, the following results 

 will show : 



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

 f Jour. Am. Chem. Soc., xxv, 896. 



