Abstract
American Journal of Science, July.—The following are among the papers appearing in this number:—Studies of the phenomena of simultaneous constrast colour; and on a photometer for measuring the intensities of lights of different colours, by Alfred M. Mayer. The photometer was constructed in such a manner that the two tints to be compared were reduced to the same by the effects of contrast. Two discs, 13cm. in diameter, and having half of their surface removed in the shape of eight equidistant sectors, were made of thin Bristol board. Between them was placed a circle of white translucent tracing paper, and the discs were clamped together with the open sectors coinciding. The compound disc was mounted on a rotator and placed opposite two silvered mirrors inclined at an angle of 150°. The plane of the disc bisected the angle formed by the mirrors, so that the surfaces of both sides could be seen simultaneously. On rotating the disc while illuminated by daylight on the one side and by lamplight on the other, the side illuminated by daylight appeared white tinted with yellow, the other appeared white tinted with blue. A compound disc of red lead, of chrome yellow, and of white cardboard was placed on the daylight side, and an ultramarine, emerald green and white disc on the lamplight side. The greenish-blue produced by the latter combination made the light blue on the lamplight side appear faintly orange-yellow by contrast, while on the other side of the ring the orange-yellow disc had diminished the orange-yellow tint of the ring to the same feeble orange-yellow as seen on the other side. —On the ammonium-lead halides, by H. L. Wells and W. R. Johnston, and on the rubidium-lead halides, and a summary of the double halides of lead, by H. L. Wells. The authors are of opinion that not one of the many complicated ammonium-lead halides described by André really exists, but that the bodies obtained by him were mixtures. They themselves succeeded in preparing five salts representing three different proportions of ammonium and lead.—A one-volt standard cell, by Henry S. Carhart. This is a calomel and zinc chloride cell adjusted to an E.M.F. of one volt by a proper concentration of the zinc chloride solution. In the bottom of the tube is pure mercury in contact with platinum wire; then follows a paste of mercurcus chloride and zinc chloride held in position by a cork diaphragm; and finally an amalgamated zinc rod immersed in zinc chloride solution of density 1˙391 at I5°C. The cell has a small positive temperature coefficient.
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Scientific Serials. Nature 48, 309 (1893). https://doi.org/10.1038/048309b0
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DOI: https://doi.org/10.1038/048309b0