3»>t; Sc'h/ilijfc Intelligence. 



Professor Ellen Glcditsch of tlie University of Kristiania a sample 

 of lead sulphide from carefully selected Norwegian cleveite. Tlie 

 lead of the sample was carefully purified, and four specific gravity 

 determinations made upon a sample of over four grams of tlie 

 metal gave closely agreeing results averaging i 1 • 2 T ; } . This spe- 

 cific gravity is lower than 1T289, the density of the Australian 

 radio-lead recently examined by the authors, while the density of 

 ordinary lead is 11-337. It is probable that the Norwegian 

 sample is a nearly pure isotope. The atomic weight of this 

 sample has been determined by the authors, although the details 

 have not yet been published, and it is pointed out as an important 

 fact that the atomic weight, 20608, divided by the specific 

 gravity gives the atomic volume 18-281, which is practically 

 identical with the atomic volumes of the Australian sample, 

 18-279 and that of ordinary lead, 18-277, as previously found by 

 the authors. — Jour. Amer. Chem. Soc, xxxviii, 1658. h. l. w. 



5. Theory of the Lead Accumulator. — The important practi- 

 cal problem of devising a portable dry-cell of the secondary type 

 has been recently attacked by Ch. Fery. The paper under con- 

 sideration is preliminary in so far as it deals only with the first 

 logical step in the systematic investigation, that is, a thorough 

 study of the chemical reactions which take place during the acts 

 of charging and discharging lead storage cells. The author first 

 reviews the previous work and thereby shows that the various 

 hypotheses concerning the behavior of the positive plate are so 

 divergent as to leave the whole subject in a state of confusion 

 and uncertainty. In particular he concludes that the theory 

 advanced (about 1882) by Gladstone and Tribe is incorrect. 

 According to this theory, which lias received wide acceptation, 

 the process of charging peroxidizes the red-lead at the anode and 

 reduces this compound at the cathode, first to the lower oxide 

 and then to spongy, metallic lead. The discharge may be briefly 

 expressed by the equation PbO, +2jET,SO a + Pb = 2PbtSO t + 

 2lf^O, so that both plates would be sulphated. (This reaction is 

 called "double sulphating.") On the other hand, there is com- 

 plete accord with regard to the sulphating of the negative plate, 

 the increase in the mass being accurately proportional to the 

 number of ampere-hours furnished. 



The evidence adduced by Fery will now be given in a fairly 

 condensed form. The color of the fully charged positive plate is 

 pure black whereas after discharge this electrode assumes the 

 characteristic brown color exhibited by lead dioxide when chem- 

 ically prepared. Since, however, the color of a given substance 

 often depends upon its physical condition (fineness of division, 

 etc.), and is therefore not a reliable criterion, the following 

 experimental facts are presented to throw doubt on the sulphat- 

 ing of the positive plate. The active material was removed 

 from the surface of a positive electrode and packed in a porous 

 cup surrounding a sheet of jjlatinum. A plate of zinc consti- 

 tuted the negative electrode, and the cell thus assembled had an 

 E.M.F. of 2-5 volts. Under like conditions lead dioxide chemi- 

 cally derived invariably gave 0-7 volt. A volumetric test was 



