12H 



Mr. W. Orookes. 



[Feb. 17, 



a vacuum. At first only a green glow can be seen ; as the exhaustion 

 gets better a little blue phosphorescence conies round the edges. At 

 a high exhaustion, on passing the current the green and blue glows 

 are about equal in brightness, but the blue glow vanishes imme- 

 diately the current stops, while the green glow lasts for an hour 

 or more. In the phosphoroscope the blue glow is only seen at a 

 very high speed, but the green glow is seen at the slowest speed, and 

 the body is almost as bright in the instrument as out of it. Some 

 parts of a crystalline mass of blende which, under the action of 

 radiant matter, leave a glow with a bright blue colour, leave a green 

 residual light when the current ceases ; other parts which glow blue 

 become instantly dark on stopping the current. 



The different action of calcium, barium, and strontium on the con- 

 stituents of yttrium is an additional proof, if confirmation be needed, 

 that the bodies I have provisionally called Ga, G/3, GS, &c.,* are sepa- 

 rate entities. It may be as well here to collect together the evidence 

 on which I rely to support this view. I will take the bodies 

 seriatim : — 



Ga. — An earth phosphorescing with a blue light, and showing in 

 the spectroscope a deep blue line, of a mean wave-length 482. 

 This earth occurs in different proportions in purified yttria from 

 different minerals. Samarskite, gadolinite, hielmite, monazite, xeno- 

 time, euxenite, and arrhenite contain most Ga, whilst fluocerite and 

 cerite contained notably less of this constituent. The addition of 

 lime brings out the phosphorescence in Ga in advance of that of the 

 other constituents. The behaviour in the phosphoroscope of Ga when 

 mixed with the alkaline earths also points to a difference between it 

 and its associates. With lime the blue phosphorescent band of Ga 

 comes into view at a very low speed, the order of appearance with a 

 small quantity of lime being G/3, Ga, G(>, and with a large quantity 

 of lime, G£, Ga, G/3. Employing strontia instead of lime, the order 

 of appearance in the phosphoroscope when the quantity of strontia 

 is small is G/3, Ga, G17, and when the quantity of strontia is in excess, 

 Ga, Giy, G/3. Baryta in small quantity brings out the lines in the 

 phosphoroscope in the following order : G/3, Ga, Giy, but when the 

 baryta is in excess the order is G/3, G17, Ga. The chemical position 

 taken up by Ga in the fractionation scheme precludes it from being 

 due to the bodies I have called G/3, G7, Ge, G£, S7, or SS. It closely 

 accompanies G£ (the earth giving the citron line), concentrating at 

 the least basic end, and I have not yet succeeded in effecting a sepa- 

 ration of the two. If, therefore, Ga is not a separate entity, its blue 

 line must be due to the citron-band-forming body called Gd. The 

 difference between Ga and Ge> is brought out in a marked manner by 



* 1 Koy. Soc. Proc.,' vol. 4Q, 1886, p. 502. 



