1887.] 



On Radiant Matter Spectroscopy. 



117 



Yttrium. 



Barium. 





Per cent. 







Per cent. 



- 





r 



In the radiant matter tube all these mixtures give 





similar spectra. The &fi green is a little brighter 



20 



80 | 



and the Grd citron is a little fainter than in the cor- 



15 



85 J 

 90 j 



responding mixtures of yttrium and calcium, but 



10 



the whole of the yttrium lines are seen. In the 



5 



95 1 

 1 



phosphoroscope the Gr/3 green is the first to appear, 

 then the Gttj red. The Go citron is not visible at any 





L 



speed. 



1 



99 



Bed line of Gtt? is much brighter ; GrS is very faint, and 







the green of Gr)8 is stronger. In the phosphoroscope 

 the order of appearance is, — first the line of Gr;8, then 











the red line of Grtj. 



0-5 



99'5 



Phosphoresces with difficulty, of a light blue colour, 

 but turns brick-red in the focus of the pole. Spectrum 

 very faint. Order of appearance to phosphoro- 

 scope : — Grj8 first, the others too faint to be seen. 



The next experiments were tried with strontium, to see what modi- 

 fication the addition of this body to yttrium would produce. The 

 following mixtures of ignited sulphates were experimented with : — 



Yttrium. Strontium. 



Per cent. 

 95 



80 



60 

 40 



35 



25 

 15 



5 



0-5 



Per cent. 

 5 



20 



40 

 60 



75 

 85 

 95 

 99 



A very good yttrium spectrum. In the phosphoroscope 

 the order of appearance is — Pirst the green of G-0, 

 then the Gra blue, lastly the Onj red. No GcB citron 

 hue could be seen, 

 j In the phosphoroscope the green of G-0 is very promi- 

 nent at a low speed, standing out sharply against a 

 black background. With a higher velocity the Gra 

 and Get] lines come into view, 

 f | The ordinary spectrum of this and the neighbouring 



mixtures is very rich in the citron line of Gr£, but I 

 entirely fail to see a trace of this line in the phos- 

 phoroscope at any speed. The line of Grj3 is the first 

 to come, then the blue line of Gra. 

 At about this point a change comes over the appearance 

 in the phosphoroscope. The blue line of Gra is now 

 the earliest to appear, and it is followed by the G-tj 

 red and GryS green. No Gr£ line is seen. 

 These mixtures are very similar to each other in the 

 phosphoroscope. The line of Gra comes first, next 

 the Grr] line, then Gr/8 hne. No Gr£ citron line has 

 been seen in any of these mixtures. 



In a paper read before the Royal Society, June 18th, 1885*, I 

 described the phosphorescence spectrum given by a mixture of 



* 'Phil. Trans.,' 1885, Part II (p. 716). 



