Abstract
Poggeendorff's Annalen, 1870, No. 7. The contents of this Number are:—(I.) “On the effect of Roughness of Surface on the Radiation of Heat,” by G. Magnus. The author shows that the generally accepted explanation of the increased emission of radiant Heat by roughened surfaces, that it depends on a diminution of superficial density, is inadmissible. He attributes it to the refraction which takes place at the surface of emission, whereby the direction of the rays which leave the surface obliquely is changed. (2.) “On the Specific Gravity of Alcohol and of Mixtures of Alcohol and Water, by E. H. Baumhauar. A defence of the author's tables of the specific gravity of alcohol against Mendelejeff's criticisms contained in Poggendorff's Annalen for 1869, vol. 138. (3.) “On the Flow of Mercury through Capillary Tubes,” by E. Warburg. The author's experiments prove that in glass tubes, whose diameter is a sufficiently small fraction of their length, the quantity of mercury which flows through them in a given time is directly proportional to the difference of pressure at the two ends, to the forth power of the diameter, and inversely proportional to the length, but that it is independent of the absolute pressures at the ends so long as the difference remains constant. He concludes from these results that there is no friction, under the conditions of the experiments, between the mercury and the glass, but that the film of mercury in contact with the glass remains at rest while the inner portions flow through it. (4.) “Continuation of Investigations into the Electromotive Force between Liquids,” by J. W. Muller. (5.) “On the Determination of the Proportion of Water in Glacial Acetic Acid, by F. Rüdorff. The author gives a table for deducing the proportion of water contained in acetic acid from the freezing point of the mixture. He gives 16.7° C. as the freezing point of pure acetic acid (without water), and finds that the presence of 1/2 per cent, of water lowers the freezing point by more than a degree. (6.) “On the Determination of the Freezing and Melting Points of Fats and other Compounds,” by F. Rüdorff. The author points out the untrustworthiness of observations of melting points made, as they often are, by heating the substance to be examined in a capillary tube, or by coating the bulb of the thermometer with it. He recommends the observation of the freezing point, with a thermometer whose bulb is actually immers. d in the substance, as a means cf establishing its chemical identity instead of observing the meltingpoint. To ascertain whether the observed temperature is the highest at which solidification can occur, he notices whether it is accompanied by rise of temperature, which always takes plce if the body has been cooled below the normal freezing point. (7.) “On the Phosphorescence of Rarefied Gases aftet the passage of an Electric Discharge, by E. Sarasin. The author finds that the presence of oxyger, either free, or combined in a compound which is probably decomposed by the discharge, is an essential condition of the occurrrence of the phosphorescence, and shows that this phenomenon is probably connected with the formation of ozone. Sulphuric acid vapour favours the production of plsosphorescence in a high degree. (8.) “On the Electromotive Forces due to the contact of different metals,” by E. Edlund. When an electric current traverses the point of junction of two different metals, a quantity of heat is absorbed or produced per unit of time which is proportional to the strength of the current and to the electromotive force acting between the metals. The author refers on this point to a previous paper (Poggendoff's Annalen, vol. cxxxvii.); in the present communication he endeavours to estimate the comparative electromotive torces acting between different pairs of metals by the heating or cooling effects of a current of measured strength. The junction formed of each pair to be examined was enclosed in the bulb of an air thermometer, and the difference between the expansions produced, when the current passed in opposite directions, was measured. The electromotive order of the metals deduced from the results did not agree with the order given by electroscopic observations (eleklrische Spannungsreihe), but it agreed with the thermo-electric order, though the electromotive forces were not found to be proportional in all cases to the thermo-electromotive forces between the same pairs of metals. (9.) On the Properties of Pictures formed by Photographic Lenses, by Dr. Hermann Vogel. The author calls attention to certain inherent defects of pictures formed by perfect photographic lenses, that is to say, defects not due to distortion or aberration in the lenses. (so.) On the Velocity of Light in Quartz, by Victor von Lang, contains very careful measurements of the deviations produced by a quartz prism in the ordinary and extraordinary rays for various angles of mcislence. Incidentally, a measurement of the ratio of the two coeflicients of expansion of quartz is also given, deduced from the change produced by alterations of temperature in the refracting sangle of the prism. (is.) On the Specific Heat of Saline Solutions and Mixtures of- Liquids, by A. Willlner. The author disputes, on the authority of the experiments made in his laboratory by Dr. Scholler, Jamin's conclusion that when two liquids are mixed together, and therefore each of them is uniformly diffused through the whole of the space occupied by the mixture, the specific heat of each increases in proportion to increased space occupied by it. (12.) On the Fusion of Leaden Bullets by striking against an Iron Plate, by Edward Hagenbach. This paper describes the melting of leaden bullets fired against an iron target, and contains a calculation showing that the kinetic energy due to the velocity assigned by competent miEtary authority is sufficient to account for the result. (13.> An Experiment on boiling together two liquids which do not mix, by August Kundt. If steam is passed into liquid sulphide of carbon, or if sulphide of carbon vapour is passed into water, the resulting mixture of water and sulphide of carbon boils at 4260 C., that is to say, at a temperature four degrees lower than the boiling point of sulphide of carbon alone. Also, if water and sulphide of carbon, which have been heated separately to between 430 and 4660, be mixed together, the nsixture boils until its temperature has fallen to about 43°. These facts are in accordance with the observation of Magnus and Regnault that the vapour-tension of a mixture of two mutually insoluble liquids is equal to the sum of tile vapour-tensions of the separate liquids. (54.) On Microscopic Tridymite, by Ferdinand Zirkel. The author describes the characters of this mineral as seen undet the microscope, and shows that it is of frequent occurrence in microscopic crystals. (15) On Acoustical Attraction and Repulsion, by K. H. Schelibach, contains experimental proofs of the statement that the sonorous vibrations of an elastic medium urge specifically heavier bod.ies towards the centre of disturbance, and specifically lighter bodies away from it.
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Scientific Serials . Nature 3, 137–138 (1870). https://doi.org/10.1038/003137b0
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DOI: https://doi.org/10.1038/003137b0