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XXVI 



THE POLARISATION OF A LECLANCHE CELL. 



By FELIX E. HACKETT, Ph.D., 

 Lecturer in Physics, Royal College of Science, Dublin ; 



AND 



R. J. FEELY, A.R.C.Sc.I. 



'a 



[Read November 27, 1917; published March 22, 1918.] 



This investigation arose out of an examination of the conditions required for 

 the accurate measurement of the internal resistance of a cell as an experiment 

 in an elementary course in electricity. It is well known that the polarisation 

 of a Leclanche cell makes it difficult to attain any precision in this measure- 

 ment. By polarisation is understood, here, the temporary change in E.M.F. 

 of a voltaic cell brought about by the passage of a current through it. During 

 a preliminary examination of the manner in which the polarisation grows 

 when the circuit is closed and decays on open circuit a theory was developed 

 which led to a simple formula for the curve of recovery of the cell. This 

 theory indicated that the decay of polarisation follows the law for the velocity 

 of bi-molecular reactions obeyed by the ionisation of gases. It will be 

 convenient to consider the results of the experimental work arranged to test 

 it under the following heads : — 



(1) General characteristics of the polarisation. 



(2) The types of polarisation shown by the recovery curve. 



(3) Summary of observations on the Leclanche cell. 



(4) The polarisation of the Weston cadmium cell. 



(1) General Characteristics of the Polarisation. 



A Leclanche cell was arranged in circuit with a variable resistance 

 adjusted by aid of a similar cell so that the initial current was - 2 ampere. 



SCIgNT. PROC. R.D.S., VOL. XV., NO. XXVI. 2 Z 



