on Secondary Batteries, 



165 



Time, in days. 



Hydrogen collected, in cubic centimetres. 



From Acid. 



From Acid containing Na 2 S0 4 . 



Per diem. 



Total. 



Per diem. 



Total. 



1 

 2 

 3 



7 



160 

 125 

 120 



75 



160 

 285 

 405 

 695 



116 

 91 

 87 

 54 



116 

 207 

 294 

 512 



It is evident that the sodium sulphate exercised a protecting 

 influence on the lead. 



In another experiment with a solution containing as small 

 a proportion of sodium sulphate as that used by Mr. Preece, 

 the protective influence was still observable, though much less 

 marked. 



These results support the idea that part of the effect pro- 

 duced ;by sodium sulphate lies in its power to diminish the 

 local actions arising between the acid and the different parts 

 of the plates. 



It is not unlikely that this chemical action has something 

 to do with the difficulty experienced in electrolytically redu- 

 cing pure lead sulphate when that substance unmixed with 

 other compounds is simply immersed in dilute acid ; for at 

 the moment of incipient decomposition the lead must be very 

 finely divided, with its affinities in their most active state. 



Sub-sulphate of Lead. 



In a paper read before the Royal Society*, Dr. Frankland 

 doubts whether the lead sulphate formed and decomposed in 

 the cell is the ordinary white sulphate known to chemists, and 

 has studied the action of dilute acid on litharge and on minium. 

 From litharge he obtained a buff-coloured compound, for the 

 composition of which he gives the formula (S0 3 ) 3 (PbO) 5 . 

 From red lead he obtained a brownish-red compound, S 2 Pb 3 O 10 , 

 Dr. Frankland thinks it highly probable that one or other of 

 these salts takes part in the electrolytic processes of the storage 

 battery. He remarks, however, very truly that the working 

 conditions in a battery are very different from those of his 

 experiments. 



* Proc, Roy. Soc. 1888. 



