138 THE UNIVERSITY OF OKLAHOMA 



plausible theory ihan the former since its valve effect is evidently 

 connected vyith making- of the aluminum-plate the anode, whereas, 

 il It were nothing more than an ohmic resistance, the film would 

 n^t pIIow Ihe passage of the currejit practically unhindered in the 

 opposite direction 



The efect of the temperature of the electrolyte upon the effi- 

 ciency of the ce'l was studied and observations were taken over a 

 cn^'-iderable lensth of time, varying conditions of cell and electro- 

 lyte, varying sizes and shapes of plates, and over a considerable 

 rano-e of temperature. It vv^as found that with an increase of t^te 

 te— D-^rature there was a decided weakening of the film. This re- 

 sulted in slight'y increased current and in a sufficient^ lowered 

 vrl^-a-^e ?o that the pov/er efficiency fell from a value of 50"^--- 

 u^ual'y ''he highest value obtainable with the electrolytic rectifier — 

 down to as low a value as 30%. Another factor introduced by the 

 hi h temperature of the electrolyte was the tendency for mere 

 of the solute to go into solution. This solute crystallized on the 

 plates when the temperature fell and the presence of these salts harl 

 a tendency to destroy the valve effect. 



It is pos.'^ible to keep ihe temperature down by means of a 

 cooling devire bu^" for the greater amount of the work these high- 

 current long runs are not necessary and the use of the Nodon 

 Valve in the 'aboratory is not greatly impaired. Large currents 

 u~ed for short times and small currents used for long times cause 

 little or no lowering of the efficiency. The rectifier wi'l there- 

 fore lend itself well to mo^t ures of direct current in a sina'I labora- 

 tory. The only care that need be given it is thut of lifting the 

 plates out of the solution when not in use and removing any excess 

 solute undissolved at ordinary temperatures so that the tendency of 

 salts to crystallize on the plates is removed. Sodium bicarbonate 

 solution serves very well as an electrolyte; the chemically pure salt 

 is not essential. It is ntjt necessary to renew it or change the solu- 

 tion very often as there is practically no breaking up of the com- 

 pound. In fact one charge was used for three years with little or 

 no apparent dimiinution in the efficiency of the rectifier. 



The writer's experience has been that the use of the mercury 

 arc is rather limited. While one can get strong currents at rather 

 hijh efficiencies from a mercury arc the cost is rather high and, if 

 expense of bulb renewals is taken into consideration, the cost soon 

 approaches that of a motor generator set, which, for all purposes, 

 is much more satisfactory. The mercury arc cannot operate on 

 small currents since considerab'e current is required to maintain the 

 arc. A few years ago, with the advent of the "movie," the mercury 



