Rc.zfic;os.
I 36
means of a revolving cathode and scraper it is possible to remove the metal as fast as formed or after it has reached any desired degree of thickness. I n this way the metal is renioved froni tlie action of tlie IV. D.s. bath and polarization is largely avoided.
On Potential Differences a t the Surfaces of Dilute Solutions. 0.I;. Tower. Zeit. phjr~.C h i l i 20, r9S ( 1 8 9 6 ) . This paper is intended to show that Planck's forniula is applicable to a cell of tlie type iUnO, ! Acid 1 KC1 1 Acid I MnO, and that tlie electromotive force of these cells differs from that of the conibiiiatioii MnO, I Acid! Acid I MnO, chiefly by the potential difference between the acid solutions in tlie latter case. His experiments confirni both conclusions fairly well, the error being about one millivolt in a total of thirty. Sodium chlorid satisfies tlie second conclusion better than potassium chlorid, rather to the author's surprise. T h e author has not shomn that Planck's forniula requires tlie second conclusion to be fulfilled when the migration velocities of tlie cation and anion are equal in the salt solution ; but assumes it as self-evident. One interesting fact appears in the paper, that Zn 1 Zii(NO,,), does not give a constant potential difference. T h e author does not refer this to the action of metallic zinc on zinc nitrate as he should. I t would be interesting to know what hypothesis could be devised in respect to wliicli the experiment recorded in table I O , page 206, could prove JP-. D. B. anything either way. The Electrolytic Decomposition Tension of Melted Zinc Chlorid. R. Lomiiz. Zcit. anoig.. Chem. 12, 272 ( 1 8 9 6 ) . Melted zinc chlorid was decomposed between carbon electrodes at a potential difference of 1.5 volts. Since the temperature was higher than that at which zinc melts the zinc dropped down from the electrode. It would have been very interesting to have had some deterininations of the cathodic polarization under these circumstances. JV. D. B.
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31, line 8 : for 7i=k, read 71-h.
