Abstract
Poggendorfj's Aunalen der Physik und der Chemie. No. 3, 1873.—This number commences with a paper by Dr. Oudemans, jun, on the influence of optically inactive solvents on the rotatory power of optically active substances. The author, employing a Wild polaristrobometer and lime-light, experimented with cane-sugar, cinchonin, brucin, phiorizin, and other substances, with water, chloroform, alcohol, ether, &c., as solvents. He unexpectedly found that the specific rotatory power of cinchonin in various mixtures of alcohol and chloroform had not values entirely intermediate between those of cinchonin in either solvent separately (which are 212° and 228°). It rises to a maximum of over 237° in a mixture of 10 per cent, alcohol and 90 per cent, chloroform. He further compared the influence of different solvents on the specific rotatory power of active substances, with their solvent action, and he considers the greater values of the former property correspond with a greater solubility of the active substance. The numerical results are given in full.—Julius Thomsen continues his “Thermochemische Untersuchungen,” examining, in this paper, the affinities of the constituents of water, of sulphuretted hydrogen, of ammonia, and of catburetted hydrogen. He finds that while there is development of heat in the formation of marsh gas, there is absorption in the formation of ethylene and acetylene, from carbon and hydrogen. The author gives a résumé of results from the series of researches here terminated (the affinity of hydrogen to the metalloids), which presents some points of considerable interest.—In the next paper Prof. Lubimoff of Moscow calls attention to an error current in most text-books on physics. The field of view in a Galilean telescope is stated to depend on the size of pupil of the observer's eye, and to be measurable by the angle under which this will appear from the centre of the object-glass. This, he says, gives a value five or six times smaller than the actual, which is directly dependent on the size of aperture of the object-glass. lie explains and illustrates his new theory at some length.—F. Rüdorff contributes the first part of a paper on the solubility of saline mixtures, and Ed. Ketteler continues his mathematical inquiry into the influence of astronomical motions on optical phenomena.—Among the extracted papers may be specified those by Edlund on galvanic resistance, by Braun on direct photography of the solar protuberanecs, and by Baumhauer on hygrometry in meteorological observatories.
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Scientific Serials . Nature 8, 95 (1873). https://doi.org/10.1038/008095a0
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DOI: https://doi.org/10.1038/008095a0