

1891.] Chemistry of the Plante Cell. 105 



sion of a trace of air. In 20 hours nearly 3 grs. of silver were 

 volatilised. The deposit of silver was detached without difficulty 

 from the glass in the form of brilliant foil. 



III. "A Study of the Plante Lead-Sulphuric Acid-Lead Per- 

 oxide Cell, from a Chemical Stand-point. Part I." By 

 G. H. ROBERTSON. Communicated by Professor ARMSTRONG, 

 F.R.S. Received May 27, 1891. 



(Abstract.) 



The author, in the introduction, states that though, since Frankland 

 in 1883 published his first" Contribution to the Chemistry of Storage 

 Batteries," the capabilities of the Plante cell have been well tested 

 and are now thoroughly understood, there is still considerable uncer- 

 tainty as to the precise nature of the chemical changes which attend 

 their use ; and that it was principally to study the part played by the 

 electrolyte that the investigation, the results of which are recorded in 

 this paper, was instituted about a year ago at the Central Institution 

 at Dr. Armstrong's suggestion, as McLeod's observations on the 

 electrolysis of sulphuric acid solutions led to the supposition that the 

 changes occurring in the acid were probably less simple than was 

 commonly supposed. This supposition was verified. 



The first section of the paper deals with the nature of the lead salt 

 formed during discharge. It is pointed out that, as is well known, red 

 lead varies considerably in composition, generally containing a smaller 

 proportion of peroxide than is represented by the formula Pb 3 4 = 

 Pb0 2 2PbO ; and that with nitric acid it behaves as though it were a 

 mixture of the two oxides, the nitric acid always dissolving out the 

 monoxide. There is no reason why sulphuric acid should not behave 

 similarly, and, since lead sulphate is but very slightly soluble, red 

 lead may be expected always to yield a corresponding sulphate, i.e., a 

 mixture of peroxide and sulphate, containing an amount of sulphate 

 corresponding to the amount of monoxide originally present in com- 

 bination with the peroxide. At Dr. Armstrong's request a number of 

 experiments were made at the Central Institution (long prior to the 

 reading of Messrs. Gladstone and Hibbert's papers) by two students, 

 Messrs. Briggs and Ingold, on various samples of red lead, with the 

 result that the sulphate formed always corresponded to the monoxide 

 originally present. 



As no proof of the existence of a definite homogeneous sulphate 

 corresponding to red lead can be afforded by analysis alone, evidence 

 must be obtained that the product differs in some of its properties 

 from a mixture. 



