New Secondary Cell for Electrical Storage. 113 



are such as to have an important practical bearing on the 

 future of electric work. 



The experiments comprised lead amalgamated with mer- 

 cury as a positive electrode, with negative electrodes 

 composed of either zinc, iron, or copper ; in each case the 

 solution between the electrodes being a salt of the metal 

 composing the negative electrode. With zinc a solution 

 of zinc sulphate was used ; with iron, sulphate of iron was 

 the solution ; and with copper, sulphate of copper. 



In all these cases the results were not only far more 

 powerful than any form of cell I had hitherto devised, but 

 also remarkably constant. 



The cell with zinc negative electrode I discarded, owing 

 to the necessity there would be to keep the zinc plate 

 amalgamated to prevent local action ; the iron negative cell 

 being set aside owing to the iron oxidising when not in 

 use. In both the zinc and iron negative elctrodes the evil 

 effects only show when the cell is charged. 



The cell having a negative electrode of copper is the one 

 I have adopted as a thoroughly economical, lasting, and 

 practical form of storage reservoir. The chemical changes 

 in this cell are exceedingly interesting and beautiful. 



The cell is composed of a .sheet of lead cleaned with 

 dilute sulphuric acid, and amalgamated thoroughly 

 with mercury, and a sheet of thin copper, a little 

 shorter ; the two sheets are perforated with a number of 

 holes. The copper is placed uppermost, and separated by 

 bands of rubber, having pieces cut out every few inches, 

 the whole being rolled into a spiral ; the object of the holes 

 in plates and pieces cut out of rubber being to allow the 

 solution to have free access to the plates. This combination 

 is immersed in a solution of cupric sulphate, and the amal- 

 gamated lead made the positive electrode of a suitable 

 source of electricity. The chemical action being the 

 oxygen of the decomposed solution, combines with the lead, 

 and forms a coating of the insoluble peroxide of lead, the 

 hydrogen replacing the copper in the solution, and metallic 

 copper being deposited on the negative electrode. As decom- 

 position of the solution proceeds it becomes colourless, and 

 more acid, until, when the whole of the copper is deposited, 

 we have the solution transformed into dilute sulphuric acid, 

 the amalgamated lead peroxidised, and pure copper deposited 

 on the negative electrode. 



During discharge the peroxide of the lead element is 



k2 



