Abstract
Wiedemann's Arinalen der Physik und Chemie, No. 8.—Limits of the solid state, by G. Tammann. Experiments on a number of organic bodies show that even when the heat of fusion is very nearly or accurately zero, the difference between the specific volumes of the liquid and the crystals is considerable.—Magnetic properties of hematite, by A. Abt. The maximum magnetic moments of three equal prisms, of pyrrhotite, hematite and magnetite respectively, were found to be in the (ratio of 1 to 2˙356 to 3˙237. Pyrrhotite shows the smallest magnetisation in comparison with its percentage of metallic iron.—The blue steam-jet, by A. Bock. A sky-blue colour is imparted to a steam-jet by sending through it a current of air saturated with hydrochloric acid. The jet, as regards colour, polarisation and diffraction, shows a close analogy with the atmosphere.—Resistance of alloys, by R. H. Weber. To measure the resistance of brittle alloys, like those of zinc and copper in which the zinc preponderates, the author employs the alloy in the form of thick plates or cylinders. A magnetic needle is made to vibrate over the plate, and its logarithmic decrement is directly proportional to the conductivity of the alloy. The method has the further advantage that the substance need not be exposed to much mechanical working, such as is involved in wire-drawing.—Work consumed in a spark gap, by E. Riecke. In a 40-plate Toepler machine, the work consumed with a gap of 2 cm. is 1˙64 watts per turn, and with a gap of 6 cm. it is 3˙27 watts. A further increase of the width of gap diminishes the work of the spark.—Pressure in the spark, by E. Haschek and H. Mache. By noting the increase of pressure in a vacuum tube on sparking, and the volume of the spark itself, the authors arrive at an estimate of the pressure within the spark. It is of the order of fifty atmospheres.—Potential gradient at the anode, by C. A. Skinner. The drop of potential from the anode to the adjoining gas during a low discharge is about 20 volts. This increases to to about 40 volts within a distance of a few millimetres from the anode; but there is no potential gradient within the thin luminous layer immediately adjoining the anode. The greater the drop of potential at the anode, the less is the potential gradient in the anode light.—A radio-active substance, by E. de Haën. By extraction from a large quantity of uranium ore, the author has obtained substances which possess the properties ascribed to “radium” in an extraordinary degree. One preparation exhibits all the properties of Becquerel radiation, and, in addition, possesses the property of being strongly luminous. This luminosity is rapidly impaired by moisture, and can only be restored by melting the substance in the oxyhydrogen blowpipe.
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Scientific Serial. Nature 60, 540 (1899). https://doi.org/10.1038/060540a0
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DOI: https://doi.org/10.1038/060540a0