IN previous publications1 I have directed attention to the fluorescence due to traces of organic substances in commercial inorganic chemicals and in minerals. What was not clear was the relation of my experiments to the somewhat similar ones of Ewles2. Recent investigations have now convinced me that we were observing two quite different phenomena. This is best shown by the following experiments : (1) Exciting alumina (Merck, for chromatography) with 254 mµ, I obtain fluorescence that is not enhanced by weak annealing and not destroyed by 1 min. at red heat, and also phosphorescence, in perfect agreement with Ewles, who had to heat his samples for hours at high temperatures to get rid of the fluorescence. I find, however, that the phosphorescence no longer appears after 1 min. at red heat and is not regenerated by adding traces of organic substances. (2) On the other hand, on exciting alumina which has been exposed to atmospheric dust with 365 mµ, there is no noticeable phosphorescence, and the fluorescence is enhanced by weak annealing, destroyed by 1 min. at red heat and regenerated by weak annealing after adding traces of organic substances.
Przibram, K., Nature, 183, 1048 (1959); 186, 300 (1960) ; Wien Anzeiger (Oct. 15, 1959 ; March 3, and June 24, 1960).
Ewles, J., and Heap, C. N., Trans. Farad. Soc., 48, 331 (1952).
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Analytical Chemistry (1962)