1894.] with a Fused Electrolyte and a Gaseous Depolariser. 57 



Fia. 1. 



polarised, and an E.M.F. calculable from the heats of combination, 

 M/C1 = MCI, is developed. If M and C are metallically connected, 

 a, momentary current passes, but the combination is immediately 

 polarised by the opposing couple, formed by the cathion of the 

 electrolyte M and the pole C. To prevent this polarisation, chlorine 

 has to be supplied at this pole. Complete depolarisation should 

 occur if the pole C consisted of a solid rod of chlorine. This is im- 

 possible, but gaseous chlorine, used as a depolariser, can be made to 

 effect more or less complete depolarisation, and should, theoretically, 

 yield as the result of its heat of combination with lead an E.M.F. of 

 1'7942 volts. In experiments made with a view to realise as nearly 

 as possible the ideal condition for preventing polarisation the cathode 

 was always molten lead. It was found that hard gas-retort carbon 

 had very little action upon molten alkaline chlorides and on chloride 

 of lead, at the temperature required for their fusion. Carbon was, 

 therefore, employed as the anode or conducting pole in most of the 

 combinations. 



The electrolyte used was either the molten chlorides of sodium and 

 potassium mixed, or chloride of lead. As there is a continuous form- 

 ation of PbCl 2 during the action of the cell, and as it is a good con- 

 ductor, it alone was finally adopted as the electrolyte. As a 

 depolariser, chlorine gas was used. Many experiments were made to 

 find a suitable way of applying the chlorine. The following are 

 details of some of the most suggestive of them. 



Exp. 1. A cell was constructed as shown in fig. 2. The arrange- 

 ment consists of an outer iron vessel, with a stratum of molten lead 



