Gooch and Kobayashi — Platinized Anode of Glass. 53 



Aet. IY. — The Use of the Platinized Anode of Glass in 

 the Electrolytic Determination of Manganese • bv F. A. 

 Gooch and Matsusuke Kobatashi. 



{Contributions from the Kent Chemical Laboratory of Yale Univ. — cclxxxix.] 



In a recent paper* we have shown that the use of very small 

 rotating electrodes of platinum in solutions of usual volume 

 (100'='"") is perfectly feasible, although the time required for 

 the complete formation of the electrolytic deposit increases 

 with the volume of the solution from which deposition is made. 

 The process was illustrated by the deposition of copper and 

 nickel upon the cathode, and of lead dioxide upon the anode. 



We have attempted, also, to effect the deposition of hydrated 

 manganese dioxide upon the very small rotating anode from a 

 solution of manganous sulphate, but in this case the special 

 difficulty is presented that the superoxidation of the manganese 

 to the condition of permanganic acid takes place under the 

 action of the higher current density implied in the use of the 

 usual strength of current and the same anode surface. Chrome 

 alum, alcohol, and formic acid, used as deoxidizing agents, 

 were introduced to effect the reduction of the permanganic 

 acid, but the results which are summarized in the following 

 statement show that the deposition of the manganese dioxide 

 upon the small anode, under the ordinary current strength, is 

 incomplete and unsatisfactory. 



Preliminary Tests. 



{Volume of solution, 100" 



"^3; anode surface, l-5<=™3 (approx.) : time, 90min.) 



Manganese 

 taken as 

 sulphate 



Manganese 



weighed as 



dioxide, 



dried at 



200° 



Initial ( 



Eeagents added to Electrolytic 

 current Solution 



grm. 



grm. 



amp. 



volt 





0-1085 



0-0337 



2-5 



16 



Acetic acid, 20^™' 

 Chrome alum, 1 grm. 

 Ammonium acetate, 5 grm. 



{)-1085 



0-0389 



2- 



17 



Alcohol, 15^"^' 



Ammonium sulphate, 1 grm. 



Sulphuric acid, 15 drops 



0-1085 



0-0275 



1- 



30 



Alcohol, 10^"^' 

 Formic acid, S''™" 



0-1085 



0-0438 



2-5 



12 



Acetic acid, 3^°^" 

 Chrome alum, 2 grm. 

 Ammonium acetate, 10 grm. 

 Alcohol, 10^°^^ 





* This Journal, xliii, 391, 1917. 



