304 



Dr. E. Frankland. Contributions to [June 20 



•where constant currents are wanted for a longer period, the working 

 of a number of elements or batteries connected by means of a com- 

 mutator in such a way that one element or battery will always be out 

 of the circuit, and have its gases changed, and be replaced in the 

 circuit at the moment when the next element or battery is switched 

 out for the same purpose. 



In using, in place of sulphuric acid, a solution of sodium chloride 

 as electrolyte, we found, after working the battery for some time, 

 sodium hydrate on one side and HC1 on the other side of the battery, 

 and have been able to determine in this case the polarisation to be 

 equal to 0*54 volt, which very nearly accounts for the difference 

 between the E.M.F. of the open battery and the E.M.F. calculated 

 according to Thomson's theorem. The E.M.F. of PtH,NaClAq,PtO 

 we found equal 086 volt, which, added to the polarisation of 

 054 volt just mentioned, gives a total of 1*40 against the theoretical 

 figure for H, = 1*47. By changing the gases after the polarisation 

 was fully established, the battery showed an E.M.F. of 1*39 volts. 



This observation, as well as the determinations of Peirce,* of the 

 E.M.F. of gas batteries with the same gases and different electrolytes, 

 s iows that the electrolyte also has considerable influence upon the 

 E.M.F. 



We hope by further investigation to arrive at assigning their 

 proper value to the various causes affecting the E.M.F. of gas 

 batteries. 



VI. " Contributions to the Chemistry of Storage Batteries. 

 No. 2." By E. Frankland, D.C.L., F.R.S. Received 

 June 18, 1889. 



Under this title I communicated to the Royal Society, in February, 

 1883, f the results of some experiments on the reactions occurring 

 during the charging and discharging of a storage cell. I showed that 

 no appreciable part of the storage effect was due to occluded gases, 

 as had been previously suggested by some chemists and physicists ; 

 but that the act of charging consisted essentially in the decomposi- 

 tion of lead sulphate whilst the discharge was produced by the re- 

 composition of this salt. 



The establishment of these, as practically the only reactions going 

 on in a storage cell, enabled me to prescribe a very simple method by 

 which the charge in any cell could be ascertained ; for as sulphuric 

 acid i3 liberated during the charging and absorbed by the active 

 material of the plates during discharge, the amount of charge could 



# 1 Wiedemann, Annalen,' vol. 8, 1879, p. 98. 



f ' Proceedings of the Koyal Society,' vol. 35, p. 67. 



