70 



Chemistry of Storage Batteries. [Mar. 1, 



resistance to the current, which is thus enabled to bring the outlying 

 portions of the coating under its influence. It may be objected that, 

 during the discharge, the work of formation would be undone ; but 

 probably, in the ordinary use of a storage battery, the discharge is 

 never completed. Thus I have found that, in a small cell containing 

 two plates 6" x 2", short circuiting with a thick copper wire for twelve 

 hours was far from producing complete discharge, for on breaking 

 this short circuit, the cell instantly rang violently an electric bell with 

 which it was previously connected. In ordinary discharges of 

 "formed " cells, therefore, the lead sulphate on the positive and nega- 

 tive plates still remains mixed with sufficient lead oxide and spongy 

 lead respectively to give it a higher conducting power than the sul- 

 phate alone possesses. 



2. Chemical Estimation of the Charge in a Storage Cell. — ~No method 

 has hitherto been known by which the charge in a storage cell could 

 be ascertained without discharging the cell; but the results of the 

 foregoing experiments indicate a very simple means of ascertaining 

 the amount of stored energy without any interference with the charge 

 itself. The specific gravity and consequent strength of the dilute 

 sulphuric acid of a " formed " cell being known in its uncharged and 

 also in its fully charged condition, it is only necessary to take the 

 specific gravity of the acid at any time in order to ascertain the pro- 

 portion of its full charge which the cell contains at that moment ; and 

 if the duty of the cell is known, the amount of energy stored will also 

 be thereby indicated. In the case of the cell with which I have 

 experimented, containing about seven quarts of dilute sulphuric acid, 

 each increase of *005 in the specific gravity of the dilute acid means a 

 storage of energy equal to 20 amperes of current for one hour, 

 obtainable on discharge, 



I hope shortly to be able to express, in terms of current from the 

 cell, the definite relation between the amount of energy stored and the 

 weight of sulphuric acid liberated. 



