CONTRIBUTIONS FROM THE JEFFERSON PHYSICAL LABORATORY, 

 HARVARD UNIVERSITY. 



STUDIES ON FLUORITE. 

 By Harry W. Morse. 



Presented by John Trowbridge October 11, 1905. Received January 11, 1906. 



I. The Fluorescence of Fluorite. 



Although the phenomena of fluorescence have been the object of 

 much research for many years the results obtained in the way of general 

 laws must be called very meagre. The law of Stokes, which appears on 

 closer investigation to have many exceptions, is almost the only general- 

 ization with direct bearing on the subject. The other general law, that 

 all substances which fluoresce show selective absorption, is of more gen- 

 eral bearing, and may perhaps be deduced directly from fundamental 

 thermodynamic principles. 



Dividing the subject matter quite arbitrarily into solids, liquids, and 

 gases, it may be said that in gases only a very few cases of fluorescence 

 have been observed. The fluorescence of sodium vapor, first observed 

 by Wiedemann and Schmidt * and lately studied with most interesting 

 results by R. W. Wood, 2 offers at least the possibility of a great in- 

 crease in our general knowledge of the subject. In gases the factors 

 determining luminescence are probably easier and more amenable to 

 experimental control than in the other states of matter. 



Among fluorescent liquids there appears a more or less general possi- 

 bility of systematization. Certain organic groups or radicals seem to 

 carry with them under definite conditions the power of conferring fluo- 

 rescence on compounds containing them, and the presence or absence of 

 the property of fluorescence may therefore be prophesied with some cer- 

 tainty from a knowledge of the chemical composition of the substance. 



With regard to the phenomena of fluorescence in solids we are without 

 any general laws or relations whatever. Those organic substances which 



1 Wied. Ann., 57, 447 (1896). * Phil. Mag. £6], 10, 513 (1005). 



