on Secondary Batteries. 



167 



action is a continuous one, which will only finish when the 

 whole of the litharge is converted into sulphate. As the 

 experiment proceeds there is an increasing proportion of in- 

 soluble sulphate present, which no doubts acts as a protective 

 coat for the unchanged litharge, and thus renders the trans- 

 formation less rapid. We found in fact that the action was 

 greatly hastened if we continually broke up the substance in 

 a mortar. 



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Time in days. 



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We see therefore no reason to doubt the view put forth as far 

 back as January 1882, that the substance produced in the voltaic 

 reaction is ordinary sulphate of lead, a substance which is 



