Chemistry and Physics 49 



respect to the commensurability of their separation. Among these complex lines 

 many cases of magnetic duplicates are pointed out. This indicates a similarity of the 

 vibrations producing such lines which will aid in the consideration of their behavior 

 under other physical conditions. An extended comparison is made of magnetic 

 separation and pressure displacement for the lines of iron and titanium, showing to 

 what degree a correspondence exists. 



No 152 NICHOLS, EDWARD L., and ERNEST MERRITT. Studies in Luminescence. 

 Octavo, 226 pages, 190 text figures. Published 1912. Price $2.00. 



This volume contains an account of researches carried on in the Physical Labo- 

 ratory of Cornell University (1903-1910) with the aid of grants from the Carnegie 

 Institution of Washington. It is a report of progress, giving results obtained by the 

 application of quantitative methods and particularly by the use of the spectrophoto- 

 meter in the study of the spectra of fluorescent and phosphorescent substances. Im- 

 portant portions of the work were done, at the suggestion of the authors, by Drs. 

 Frances G. Wick, C. A. Pierce, Percy Hodge, and C. W. Waggoner, and by Messrs. 

 H. E. Howe and Carl Zeller. 



The list of topics includes : 



Spectra-photometric studies of fluorescent solu- The luminescence of Sidot blende when ex- 



tions belonging to Lomrnel's first class and cited by Roentgen rays, its photo-lumines- 



of rhodamin, resorcin-blau, chlorophyl, cence during excitation, and its phosphor- 



uranium glass, fluorite, and ssculin. escence spectrum. 



Determinations of the absorbing power and Thg rf of phos p horescence in Sidot blende 



fluorescence of resorufin. and Qther substances . 



The influence of red and infra-red rays on 



photo-luminescence, including the effects Kathode-luminescence of willemite and Sidot 



before, during, and after excitation and blende and its dependence on current dis- 



the variation in the effect with the wave- charge and potential. 

 length of the active rays. 



Studies of thermo-luminescence: variations in The electrical properties of fluorescent solu- 



the rate of decay of Sidot blende and Hons and vapors. 



calcium sulphide as the result of heating. , . 



Fluorescence absorption. 



Phosphorescence of short duration. 



Photographic determinations of the distribu- The energy curves of fluorescence spectra. 



Sidot blende. cases of eosin and resorufin . 



Photographic studies of phosphorescence at 



room temperature, of the decay of phos- The theory of Wiedemann and Schmidt. 

 phorescence, of the effect of infra-red 



rays, and of the influence of temperature Phosphorescence from the standpoint of the 

 on certain fluorescence spectra. dissociation theory. 



No. 298. NICHOLS, EDWARD L., and H. L. HOWES, in collaboration with ERNEST 

 MERRITT, D. T. WILBUR, and FRANCES G. W r iCK. Fluorescence of the 

 Uranyl Salts. Octavo. In press. 



This book contains an account of the investigations made in the Physical Labo- 

 ratory of Cornell University between 1910 and 1918 with the aid of grants from 

 the Carnegie Institution of Washington. The pioneer work of Becquerel on the 

 spectra of the uranyl salts has been considerably extended. The fluorescence 

 spectra of these salts consist of rather narrow bands, which are arranged in 

 groups exhibiting beautiful symmetry. At the temperature of liquid air these 

 bands are resolved into components which are so narrow that they resemble lines, 

 permitting precise measurements of wave-length. The bands of the fluorescence 

 spectrum always occur in series of constant frequency interval, while the bands 

 of the absorption spectrum occur in series of shorter, but constant, frequency 

 interval. The range of wave-lengths studied includes the entire visible spectrum. 

 Excitation by the undispersed carbon arc, or by the mercury arc, or by the X-rays, 

 or by the cathode rays produces the same spectrum ; hence the bands are con- 

 sidered to form a homogeneous complex. To complete certain families of salts 

 new specimens were produced, and where possible their crystallographic axes were 

 measured. The polarized spectra of the double chlorides were measured and 

 studied, and were also found to occur in series of constant intervals. In the 

 case of four of the double chlorides the absorption spectrum was discovered 

 extending well into the fluorescence region. This overlapping of the absorption 



