1885.] On Charging Secondary Batteries. 349 



120 lbs. The plates are prepared by the Parker- Plante process 

 before insertion in the cell, those forming the positive pole being well 

 peroxidised, while those forming the negative pole are well coated 

 with spongy lead.* They are thus, when put together, prepared at 

 once to be charged. If they are not at once charged, local action sets 

 in, and lead sulphate is injuriously formed. 



4. I have cut away a small portion of the centre of the central plate 

 of each cell to admit a hydrometer having a scale graduated from 

 V050 to 1*150. The changes of the density of the liquid and of the 

 colour of the plates give the fullest and clearest indications of the 

 behaviour of the cell. The condition of the surface of the peroxi- 

 dised plate as felt by the finger is also good evidence of its condition. 

 If a plate is yellowish-brown and rough, it probably makes bad 

 contact with the lead terminal ; if black and hard, it wants the 

 density of current regulated ; if plum-coloured and greasy to the 

 touch, it is in good order, and working well. 



5. At the present time I am charging my battery twice a week, 

 putting in at each charge about 120 ampere-hours. The battery is 

 charged in two sections. During each charge observations are made 



10 II 12 13 14 



Greenwich Mean Time. 



EMF 



Current. IS Cells. 



Specific Gravity. 



* The Parker-Plante process consists in immersing for a few hours the lead 

 plates in a solution of nitric and sulphuric acids in these proportions — 



Nitric acid 1 



Sulphuric acid 2 



Water 17 



before fixing in the cells. This not only chemically cleans the lead surfaces, but it 

 favours the formation of sulphate of lead in such a way as to be readily converted 

 into lead peroxide and spongy lead on the passage of a strong current through the 

 cells. The formation of the cells is thus greatly expedited. 



