. Carnegie Institution of Washington publication. 40 FLUORESCENCE OF THE URANYL SALTS. The uranyl salts, because of their remarkable spectra, afford an unusual opportunity to establish the exact relation between the emis- sion of light during excitation and at various times after excitation has ceased, and it was for this purpose that the first experiments with the new phosphoroscope were undertaken. The method, briefly outlined, is as follows: The substance, inclosed in a flat tube of glass BA about 8 cm. long and 2 cm. wide, is viewed through the rapidly revolving sectored disk of the synchr
. Carnegie Institution of Washington publication. 40 FLUORESCENCE OF THE URANYL SALTS. The uranyl salts, because of their remarkable spectra, afford an unusual opportunity to establish the exact relation between the emis- sion of light during excitation and at various times after excitation has ceased, and it was for this purpose that the first experiments with the new phosphoroscope were undertaken. The method, briefly outlined, is as follows: The substance, inclosed in a flat tube of glass BA about 8 cm. long and 2 cm. wide, is viewed through the rapidly revolving sectored disk of the synchrono-phos- phoroscope. It is mounted vertically, with its axis at right angles to the radius of the disk, as shown in figure 29. D 1 I I. <— <-_-,—H I B FIQ. 29. FIG. 30. It is uniformly excited by zinc sparks 120 times a second while hidden by the closed sectors and is visible for 1/240 of a second during the passage of each of the intervening open sectors. A phosphorescent substance of slow decay appears under these cir- cumstances to be equally bright from top to bottom, but if one of the uranyl salts, such as the double uranyl-ammonio sulphate, which was the substance selected for detailed study, be used, it appears a very bright green at the bottom of the tube, shading off to bare visibility at the top. The rate of decay of this substance and of the other uranyl salts is so rapid that the upper end of the tube, which is seen at the intensity which corresponds approximately to the instant second after excitation, has only a small fraction of the brightness of the lower end, which is viewed about second after excitation. The particular salt mentioned above was selected because at low temperatures its spectrum is unusually well resolved in groups of com- plexes of narrow, line-like bands, making it possible to detect changes in the individual components. To obtain simultaneous observations a pair of right-angled prisms was mounted before the slit of a Hi
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