544 SCIENCE PROGRESS 



shifted towards the longer wave-lengths, with increase in the 

 atomic weight of the alkaline earth metal. Thus, the 

 phosphorescence of CaO,Cu was blue ; that of SrO,Cu green, 

 and of BaO,Cu yellow. 



The oxygen compounds require to be heated to a high 

 temperature before showing the maximum intensity and 

 duration of phosphorescence, whereas sulphur compounds 

 phosphoresce best at ordinary temperatures, and selenium 

 compounds at lower temperatures. Some of the oxide mixtures, 

 which did not phosphoresce at ordinary temperatures, stored 

 the exciting radiation, and emitted this only when heated to 

 300-400° C. There are many regularities to be observed in the 

 behaviour of the sulphur, selenium, and oxygen compounds. 

 With increase in atomic weight, both the exciting bands and 

 the phosphorescence are shifted to the longer wave-lengths. 



Tiede and Schliede {Ber., 1920, 53 [B], 1721), studying the 

 phosphorescence of zinc sulphide, conclude the crystalline forms 

 of this substance do not show phosphorescence. Neither 

 wurtzite (hexagonal) nor sphalerite (in the pure condition) is 

 capable of this phenomenon. The fused salt and the crystalline 

 forms in the presence of a flux may, however, be excited by 

 light. Pure barium sulphide also phosphoresces in the fused 

 condition without the presence of a binding material. 



The fluorescence of iodine is apparently a property of the 

 molecule and not of the atom (Landau and Stenz, Phil. Mag., 

 1920, [vij, 40, 189). The dissociation of the iodine destroys 

 both the fluorescence and the resonance spectra. The com- 

 pHcated vibrating spectra, corresponding with thousands of 

 lines in the visible part of the spectrum, is not inherent in the 

 atom, but in the molecule. Thus, the iodine atom will possess 

 a simple structure. 



Other papers on this subject are : 



" The X-ray Fluorescence of certain Organic Compounds," Newcomer, 

 J.A.C.S., 1920, 42, 1997; "Existence of Intermediate States in the 

 Phosphorescence of Calcium Sulphide, deduced from a Study of its Con- 

 ductivity," P. Vaillant (C.R., 1920, 171, 713) ; " Fluorescence, Dissociation, 

 and lonisation in Iodine Vapour," Compton and Smyth [Science, 1920, 51, 

 571) ; " Fluorescence of the Uranyl Salts," Nichols, Howes, Merritt, 

 Wilber, and Wick {Carnegie Inst. Washington Publication, 1919, 298, i) ; 

 " Bioluminescence. Ill, The Production of Light by Luciola vitticollis 

 is an Oxidation Process," Sakyo Kanda [Amer. J. Physiol., 1920, 53, 137). 



OKGANIC CHEMISTRY. By P. Haas, D.Sc, Ph.D., University College, 

 London. 



Two papers dealing with the constitution of polysaccharides 

 deserve attention. In the first one, on " The Relationship of 

 Inulin to Fructose " (Irvine and Steele, /. Chetn. Soc, 1920, 



