General and physical chemistry

1899 Journal of the Chemical Society Abstracts  
Magnet-radiometer. By NICOLAE TECLU (J. pr. C h m . , 1898, [ ii], 58, 255-260. Compare Abstr., 1893, ii, 401).-The paper contains a detailed description and photograph of the " magnet-radiometer " designed by the author for use in the diaphonometer previously described by him (Zoc. cit.). The outer portion of the vane of a radiometer is coated with a very thin layer of iron, so that movements of the vane can be caused, not only by the action of light rays, but also by the approach of a magnet
more » ... proach of a magnet ; when both forces are applied simultaneously, the position assumed by the vane will be a resultant of the two, and so 3an be applied to the measurement of the intensity of the light falling on the instrument. By FHAN~OIS DUPONT (BUZZ. SOC. China., 1897, [iii], 17, 584)-A much more satisfactory yellow light €or polarimetric observations is obtained when a mixture of sodium chloride and trisodium phosphate, in molecular proportions, is used in place of sodium chloride alone. By DOUGLAS MCINTOSH (J. Physical Chern., 1898, 2, 185--193).-The object of the author in undertaking this research was t o find a convenient standard having a n E.M.F. of about 0.5 volt. A cell consisting of zinc, zinc chIoride, lead chloride, and lead, as described by Baille and Fhry, gives good results, and has an E.M.F. of 0.5 at 20' when the specific gravity of the zinc chloride is 1.23. The temperature coefficient is extremely low. A great many cells in which mercuric oxide was used as a depolariser were tried, but none of these were satisfactory, and the use of other oxides as depolarisers gave negative results. Cells of copper, copper sulphate, mercurous sulphate, and mercury were tried and gave excellent results. The copper sulphate and mercurous sulphate are each taken in the form of a paste. The E.M.F. of this cell decreases with rising temperature, and in the neighbourhood of 1 6~5~ may be calculated by the formula E = 0.3613 + (16.5 -t)0*0006 volt. Cells containing Pb, PbCl" Hg,CI" Hg were also examined, and gave satisfactory results. The E.M.F. increases with the temperature, and may be calculated approximately between 15' and 21° by the formula Determination of Polarisation. By KARL HEIM (Zeit. Elektl.0chem., 1898, 4, 527).-In a n electrolytic cell of resistance R, with insoluble anode, through which current C is passing with E.M.F. = 3, we have E = p + CR, where p is the polarisation. If a thin sheet of metal be interposed between the electrodes so as to divide the cell completely, without sensibly affecting its resistance, and the current be maintained unchanged, we -have E' = 2p + CR, or p = ,&' -E. I n putting the method into practice, the main difficulty is encountered in arranging the cell so that the third electrode may be put in or taken VOL. LXXVI. ii. 6
doi:10.1039/ca8997605077 fatcat:ub4kzdgj4fg2ld4abchub7wn3e