624 



PHYSICS, PROGRESS OF, IN 1893. 



Color of Ions. Ostwald ("Journal of the 

 Chemical Society," October, 1892), in experi- 

 ments on the color of ions, finds that the spectra 

 of dilute solutions of salts having the same col- 

 ored ions are identical ; for example, the per- 

 manganates give the same values for the absorp- 

 tion bands whatever the base. 



Electric Heating. Henri Moissan (Paris Acad- 

 emy, May 29) has succeeded in distilling the most 

 refractory substances by the heat of the voltaic 

 arc. Quartz and zircon were fused almost in- 

 stantly, boiled in a few moments, and finally 

 vaporized ; tungsten was cast in ingots. Again 

 (ibid., June 12) 30 grammes of copper were vola- 

 tilized in five minutes ; silver distilled easily, 

 condensing chiefly in globules varying from mi- 

 croscopic dimensions to the size of small shot, 

 but partly in arborescent fragments. Platinum, 

 aluminum, and tin were also distilled, the last 

 condensing partly in a curious fibrous form. The 

 distillation of gold is peculiarly interesting, the 

 metal condensing in powder of beautiful purple 

 sheen to the naked eye, but appearing under the 

 microscope as minute spheres of the usual yellow 

 color. On the cover of the furnace three annular 

 deposits were found, of which the inner consisted 

 of yellow globules of considerable size, the next 

 of smaller ones, deep red, the outer of a purple 

 sublimate. Carbon is first converted into graph- 

 ite and then distills over, condensing in light semi- 

 transparent brown plates, seeming to constitute 

 a distinct allotropic variety. Even refractory 

 alkaline earths, like magnesia and lime, have 

 been distilled by this process. J. Violle (ibid., 

 Dec. 26, 1892), from calorimetric measurements 

 with part of the carbon detached from the hot- 

 test part during the passage of the current, finds 

 the temperature of the voltaic arc (and therefore 

 that of the volatilization of carbon) to be 3,500. 

 This remains constant, no matter what power is 

 employed. Lagrange and Hoho (Bulletin of the 

 Belgian Royal Society. No. 2) produce an arc by 

 using a graphite electrode in sulphuric acid. A 

 layer of gas forms around the electrode, and 

 since nearly the whole resistance is concentrated 

 here, the whole of the energy is transformed into 

 heat there. The temperature depends only on 

 the strength of the current. By this process the 

 heating is not only intense but rapid. When 

 one electrode is a bar of steel one centimetre 

 thick (Paris Academy of Science, March 13), the 

 other having a large surface, it was found on 

 breaking the current that the liquid, cooling the 

 bar, had imparted a brittle structure only to a 

 superficial layer, the rest not having been heated. 

 J. Klemencic (Vienna " Berichte," March 16) has 

 investigated the heating effect of electric vibra- 

 tions and concludes that the resistance to the 

 passage of very rapid vibrations depends on the 

 magnetizability and the kind of wire. 



Photo-electricity. E. Branly (Paris Academy 

 of Science, April 20) finds that a disk of polished 

 aluminum slowly loses its charge, and that this 

 loss is equal for positive and negative charges 

 and independent of the kind of light. If the 

 disk has been freshly polished the loss is rapid 

 even in diffused light, and is only slightly di- 

 minished by orange glass. From experiments 

 on the effect of light on silver (Asiatic Society 

 of Bengal, May), it appears that sunlight has an 

 oxidizing effect on that metal, whether in acids 



or in alkalies, and that the exposed plates become 

 relatively positive. 



Phenomena in Solutions. G. H. Zahn (Wiede- 

 mann's " Annalen," No. 4) finds that when a cur- 

 rent is passed across the boundary between two 

 solutions of different degrees of concentration, 

 there is an alkaline reaction above the boundary 

 in the dilute solution, in case the current passes 

 from the concentrated to the dilute, and a depo- 

 sition of solid hydrates. The salts experi- 

 mented with were those of barium, strontium, 

 aluminum, iron, manganese, and zinc. 



Magnetic Action of Induced Currents. Elihu 

 Thomson (" The Electrician ") has discovered 

 an apparent attraction of a copper disk by an 

 alternating magnetic pole when the diameter of 

 the disk is smaller than that of the pole. At 

 some distance from the pole the disk is repelled, 

 but the repulsion diminishes as it moves nearer, 

 and finally gives place to attraction. The ex- 

 planation is that the induced currents in the 

 disk, on account of its small diameter, do not 

 suffer so great a lag as those in the rings that 

 surround the pole; hence the repulsion is finally 

 overcome by the attraction between the currents 

 in the disk and the iron core. 



Piezo-electricity. Dr. G. Gore (" Philosophical 

 Magazine," February) finds that when a long 

 vertical tube is filled with an electrolyte a cur- 

 rent traverses it. When the tube is reversed the 

 current reverses, and there is no current when 

 the tube is horizontal. The effect varies with 

 the liquid and with the metal employed for the 

 electrodes, being greatest with zinc and potas- 

 sium chloride. In 91 trials, 41 currents were 

 obtained, of which 39 were upward and 2 down- 

 ward. It was proved that difference of pressure 

 without difference of altitude would give rise to 

 a current, and that the effect was not due to 

 thermoelectricity, In all cases the current re- 

 sults not only from a difference of electro-motive 

 force, but primarily from the influence of pres- 

 sure on the electric potential of the metal alone 

 and the liquid alone. There seems to be a direct 

 transformation of mechanical into electrical en- 

 ergy, and a discovery of its mechanism would 

 doubtless be a solution of the whole question of 

 electro-motive force. A. P. Chattock (ibid., De- 

 cember, 1892) thinks that the phenomena of 

 pyro- and piezo-electricity are accompanied by 

 relative motion of two sets of initially and op- 

 positely charged molecules distributed through- 

 out the crystal, and concludes that chemical 

 affinity and ionic attraction are possibly the 

 same. Kelvin (ibid., October) has constructed a 

 piezo-electric pile of 24 double plates of zinc and 

 copper resting at the corners on India rubber. 

 When the poles are connected with a galvanom- 

 eter and a weight is allowed to fall on the pile, 

 a considerable deflection results. The author 

 (ibid., November) suggests that a model of a 

 crystalline molecule might be thus constructed. 



'Effect of Points. Julius Precht (Wiede- 

 maiin's " Annalen," No. 5) finds that points may 

 be charged very highly, a lightning conductor 

 taking 15,000 volts and the finest points 2,500. 

 The ultraviolet rays favor such charge, but it is 

 diminished by dus't. A bundle of equal points 

 requires a higher potential than a single one. 



Magnetism. Magnetization H. Lehmann 

 (Wiedemann's "Annalen," No. 3) has investi- 



