270 



NICHOLS— EFFECTS OF TEMPERATURE 



[April 22, 



When a body capable of phosphorescence is either heated or 

 cooled and then exposed to light the intensity of its fluorescence is 

 found to vary as are also the intensity and duration of its phos- 

 phorescence. Mere observations with the unaided eye suffice to 

 show the following: 



1. Very great changes occur in the rate of decay as the result 

 of either cooling or heating. 



2. The color of phosphorescence frequently differs at different 

 temperatures. 



3. The color of phosphorescence may be seen to vary markedly 

 during decay, one tint gradually merging into another. 



Fig. 2. Apparatus for cooling. 



4. Fluorescence of one color is often followed by phosphor- 

 escence of another. W. S. Andrews,'' for example, has noted the 

 following in the case of artificial phosphorescent substances. 



Compounds containing. Fluorescence. Phosphorescence. 



(0) Zinc and manganese. light pink deep red 



{h) Cadmium, manganese and sodium, light pink orange-yellow 



(c) Cadmium and manganese. yellow light green 



° Andrews, W. S., Science, Vol. XIX., p. 435, 1904. 



