PHYSICS. 507 



a solid black amorphous substance, having the composition Cu H2 O4, 

 and which, from its characteristic property of being transformed into 

 mellitic acid by oxidizing agents, they call mellogen. If phosphoric 

 acid be electrolyzed, a similar body is formed, which, since it contains 

 phosphorus, they call phosphomellogen. (J. Phys., December, II, i, p. 

 571.) 



Krouchkoll has experimented to determine whether the variation of 

 the friction produced in the electromotograph of Edison by the passage 

 of a current is a result due to electrolysis. His apparatus consisted of a 

 shallow glass dish, having a piece of polished glass at bottom, placed 

 on a horizontal metal disk, rotated about a vertical axis by means of a 

 small Gramme machine,* a rubber made of a series of small brushes of 

 platinum wire, fixed in ebonite, rubbed against the glass during the 

 rotation, tending to carry with it the needle of a sensitive balance, to 

 which it is fastened. In the dish was sulphuric acid diluted with five 

 parts of water, which moistened the brushes. One pole of the battery 

 was connected to the brushes; the other was fastened to a copper strip 

 immersed in copper sulphate solution to avoid jjolarization. This solu- 

 tion was contained in a porous cup, immersed in. a second porous cup con- 

 taining water and standing in the acid in the dish. On starting the 

 movement of rotation and adjusting the balance to equilibrium, it is 

 easy to show by the inclination of the needle that the polarization by 

 oxygen increases the friction and that polarization by hydrogen dimin- 

 ishes it. Half a Daniell cell is quite sufficient for the experiment, though 

 the efiect increases with an increase of the electromotive force used. 

 {Comptes Eetidus, July, xcv, p. 177.) 



Plants has found that the lougi)rocess of forming his accumulators is 

 shortened if they are warmed during charging. The temperature best 

 for this purpose is between 70° and 80° C, at which limit the opposing 

 electromotive force is somewhat less than when cold, and the resistance 

 very much less. He does not find it advantageous to exceed this limit. 

 Thompson suggests that the reason may be that at the above tempera- 

 ture the gases are evolved under normal conditions, no ozone being 

 formed. {Nature, February, xxv, p. 376.) 



Gladstone and Tribe have published a series of valuable papers on the 

 chemistry of the Plants and Faure accumulators, in which they have 

 considered (1) local action, (2) the charging of the cell, (3) the discharge 

 of the cell, and (4) the function of sulphate of lead. {Nature, xxv, pp. 

 221, 4GL ; xxvi, pp. 251, 208, 342, 590, 002.) 



A sub-committee of the experimental jury of the Electrical Exhibition 

 has tested in the Conservatoire des Arts et Metiers the efficiency of the 

 Faure secondary battery. Thirty-five accumulators of the spiral form, 

 each in a stoneware pot 35'=™ high and 25'='" in diameter, were charged 

 in series by the current from a Siemens dynamo driven by a steam en- 

 gine. The working electromotive force of an accumulator was found to 

 be from 2.08 to 2.17 volts. The battery was charged for 22 hours 45 miu- 



