1887.] 



On Radiant Matter Spectroscopy. 



121 



in very small quantities with lime, the lines of Gh and Got are 

 intensified, while that of Gfi is weakened. This new result seems to 

 show that if only a small trace of G(3 is present with lime and 

 lanthanum, the green line is not only suppressed, but the quenching 

 action has actually extended so far as to neutralise that part of the 

 continuous lime spectrum having the same refrangibility as the G/3 

 line, the result being a black space in the spectrum. In the phos- 

 phoroscope the line of Gre is visible at the slowest speed ; GS comes in 

 at an interval of 0'0035 second, and the Ga. line immediately after- 

 wards. 



Lead sulphate, by itself, in the radiant-matter tube glows with a 

 nearly white colour, giving a continuous spectrum. In the phos- 

 phoroscope the red and orange are cut off, leaving a strong concen- 

 tration of light in the green and blue. 5 per cent, of lead added to 

 calcium sulphate phosphoresces like lime. 



Magnesia phosphoresces pink. 5 per cent, with lime, as sulphates, 

 give a greenish phosphorescence, with a tendency to turn red as the 

 powder heats. As the Oriental ruby contains between 1 and 2 per 

 cent, of magnesia, a mixture was prepared of acetate of alumina 

 with 2 per cent, of magnesia, and tested after ignition. It gave no 

 spectrum or lines. This was done to see if the crimson line of 

 aluminium might be due to the presence of magnesia. 



Niclcel added to calcium sulphate in the proportion of 5 per cent, 

 makes no alteration in the usual phosphorescent phenomena of 

 calcium. 



Potassium, 5 per cent., added to calcium sulphate gives a bright 

 phosphorescence, and made the residual glow very persistent. 



Samarium. — The phosphorescent behaviour of this body, alone and 

 mixed with other substances, has been fully described in my paper on 

 samarium.* 



Scandium, either in the form of earth or sulphate, phosphoresces- 

 of a very faint blue colour, but the light is too feeble to enable a 

 spectrum to be seen. Addition of lime does not bring out any lines. 



Sodium sulphate mixed with an excess of calcium sulphate gives a< 

 greenish tinge to the usual colour of the phosphorescence. The- 

 sodium line is visible in the spectrum. 



Strontia in the radiant-matter tube glows with a rich blue colour,, 

 showing in the spectroscope a continuous spectrum with a great 

 concentration of light in the blue and violet. In the phosphoroscope 

 the colour of the glow is bright green, showing in the spectroscope a 

 continuous spectrum, with the red and blue ends cut off. A mixture- 

 of calcium sulphate with 5 per cent, of strontium sulphate behaves, 

 like calcium sulphate alone. 



* 'Phil. Trans./ 1885, Part II (pp. 709—721). 



