Relation between the Electromotive Force of a Clark Cell and the Density of the Zinc Sulphate Solution

H. S. Carhart
1892 Transactions of the American Institute of Electrical Engineers  
It is now well known that there is an inverse relation between the E. M. F. of a Clark cell and the density of the solution of zinc sulphate; that is, an increase in the density of the solution is accompanied by a decrease in the E. M. F. of the cell. This relation for the Daniell cell I investigated ten years ago.' A similar investigation for the Clark cell was recently undertaken at my suggestioni by two students in my laboratory, Mr. T. E. Barnum and Mr. E. A. Cheney. They have also
more » ... have also undertaken to determine whether the teinperatnire coefficient changes with a change in the denisity of the solution, provided there are no crystals of zine sulphate present. The importance of this investigation is connected with the fact that the temperature coefficient of the Clark cell containing zinc sulphate crystals is almost exactly double the value exhibited by cells containing no crystals. Lord Rayleiglh's value is 0.00077 at 15°C.;2 Dr. Flerning found 0.00082 for cells with crystals. My owrn cells, containing no crystals, have a coefficient of 0.000386 per degree C. at 150.3 Dr. Kalhle in Berlin has obtained a valtue almost idenitical witlh that of Lord Rayleigh for cells containing zinc sulphate crystals. Half of this so-called temperature coefficienit is due to the dissolving of the crystals with rise of temperature, or conversely to recrystallization when the temperature falls. A large change in the E. M. F. of a standard cell with change of tem-1
doi:10.1109/t-aiee.1892.5570468 fatcat:c3mv4vujmzb2dnx3b6vfkeyreu