. Carnegie Institution of Washington publication. FROZEN SOLUTIONS. 181 the solutions, even at —180°, resembled in breadth and regular spacing those of the solid salts at room temperature. The uranyl acetate in alcohol proved to be the exception, since at —180° it resolved into faint lines, which did not, however, coincide in position with those of the solid acetate at that temperature. The variety of shifts with systematic dilution and temperature change led to the second investigation,1 in the hope that some general law of shift might be deduced. It was also planned to study the funda- menta
. Carnegie Institution of Washington publication. FROZEN SOLUTIONS. 181 the solutions, even at —180°, resembled in breadth and regular spacing those of the solid salts at room temperature. The uranyl acetate in alcohol proved to be the exception, since at —180° it resolved into faint lines, which did not, however, coincide in position with those of the solid acetate at that temperature. The variety of shifts with systematic dilution and temperature change led to the second investigation,1 in the hope that some general law of shift might be deduced. It was also planned to study the funda- mental relations between concentration and frequency interval, temperature, and state of resolution, etc. With these relations in view much work was done which led to the discovery of many beautiful and unique spectra. EXPERIMENTAL METHOD. For the study of the spectra, except where otherwise specified, a Hilger constant-deviation spectrometer was used. The apparatus for the cool- ing and excitation of the sub- stances under observation was designed to enable the observer to hold the tempera- ture of the specimen con- stant at any temperature between 0° and -180° C. The mounting consisted of a cylindrical copper block M (fig. 90), the top of which was bored to receive a small test-tube F, which contained the fluorescent solution. The side of the block was channeled to let the exciting light fall on the specimen and to let the fluorescent light out. To the bottom of this copper block was soldered a cylinder of sheet copper, which could be partially or completely covered by the liquid air in the unsilvered Dewar bulb D, thus produc- ing different temperatures in the specimen. This mount- ing was rigidly suspended from above by partially non-. FIG. 90. 1 Howes. Physical Review (2), vol. 6, p. 193. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may
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