1887.] 



On Radiant Matter Spectroscopy. 



125 



"brilliancy of the yttrium spectrum in proportion to the quantity 

 added. All the bands remain of their normal sharpness. 



Yttrium 5 per cent., copper 95 per cent., phosphoresces very 

 feebly. 



Yttrium 90 per cent., didymium 10 per cent. — This mixture gives 

 a good yttria spectrum. Yttrium 70 per cent., didymium 30 per 

 cent., phosphoresces very fairly and gives all the usual lines. 



Yttrium 50 per cent., didymium 50 per cent., refuses to phos- 

 phoresce. The tube is either too fall of gas to allow the phosphor- 

 escence to be seen or it becomes non-conducting. When the mixture 

 is illuminated by the glowing gas the absorption lines of didymium 

 the green are seen. With higher proportions of didymium the same 

 results are produced. On adding 25 per cent, of lime to the mixture 

 containing 50 per cent, of didymium the yttria spectrum is brought 

 out very well. Lime added to a mixture of 10 per cent, yttria and 

 90 per cent, didymium brings out the yttrium spectrum fairly, but the 

 tube soon becomes non-conducting. 



Yttrium 5 per cent, and glucinum 95 per cent, gives a bright phos- 

 phorescence, but the definition of the spectrum lines of yttria is bad. 



Yttrium 5 per cent., thallium 95 per cent. — No spectrum is given 

 by this mixture, it turns black and refuses to phosphoresce. 



Yttrium 5 per cent., tin 95 per cent., phosphoresces faintly, the lines 

 being very indistinct. 



Yttrium 5 per cent., titanium 95 per cent., acts like thoria, and the 

 tube becomes non-conducting. 



Yttrium 5 per cent., tungsten 95 per cent. — This phosphoresces of a 

 bright yellow colour, the spectrum is brilliant, but the lines are not 

 sharply denned. In the phosphoroscope the colour becomes greenish, 

 and the spectrum shows only the green lines of G(3. 



Yttrium 5 per cent., zinc 95 per cent. — The phosphorescence is of 

 a pale yellowish-white, and the spectrum is very brilliant, being equal 

 to that shown by 30 per cent, of yttrium with barium, calcium, mag- 

 nesium, or strontium. In the phosphoroscope the colour becomes 

 reddish, and the Gr/3 green line is the first to come. ~No citron line is 

 seen. If the yttrium contains a trace of samarium, the samarium 

 spectrum, which is scarcely seen under ordinary circumstances, now 

 comes out distinctly. 



Zinc sulphate mixed with 95 per cent, of calcium sulphate phos- 

 phoresces a bright bluish-green colour; the spectrum contains no 

 bands or lines. 



Zinc sulphide (Sidot's hexagonal blende*). — This is the most bril- 

 liantly phosphorescent body I have yet met with. In the vacuum 

 tube it begins to phosphoresce at an exhaustion of several inches below 



* ' Comptes Eendus,' vol. 62, 1886, pp. 999—1001 ; vol. 63, 18G6, pp. 188—189. 



