March lo, 1887] 



NA rURE 



449 



bodies on the phosphorescence of samarium ("On Ratliant- 

 Maucr Spectroscopy ; I'art 2, Samarium, " Phil. Trans., 

 1S85, I'art II. pp. 710-22.) The cvperiments resulting in the 

 following observations were tried at about the same time. I will 

 describe them in alphabetical order. Unless otherwise men- 

 tioned all the mixtures were in the form of anhydrous sulphates. 



Yllriiim 5 ]>er cent., aluminium 95 per cent., gives a good 

 yttria spectrum ; the blue line of Go is very distinct, and the 

 double green of G/3 is well divided. In the phosphoroscope the 

 G/3 and Go lines first appear simultaneously, then the (i5 

 line. 



Yttrium 99"5 per cent., bismuth o'5 per cent. — The spectrum 

 is bright, and on close examination a trace of samarium green, 

 G7, is to be detected forming a wing to the GS line. In the 

 phosphoroscope the citron line of G5 entirely disappears and the 

 saniarium double green line, which out of the phosphoroscope is 

 almost obscured by the great brightness of G5, now appears 

 distinctly, together with the green GS line. Yttrium 95 per 

 cent., bismuth 5 per cent., gives the usual yttria spectrum. No 

 G5 line .appears in the phosphoroscope at any speed. At first 

 only the (Jfl line is seen, and next the Go line appears, .as in 

 yttria. On gradually increasing the percentage of bismuth the 

 spectnmi of yttria grows fainter, until with 95 per cent, of 

 bismuth the phosphorescence is bad and the spectrum faint. 



Yttrium 5 per cent., cadmium 95 per cent., gives a brilliant 

 phosphorescence, but the spectrum is almost continuous. In the 

 phosphoroscope a faint concentration of light is seen in the 

 green, which becomes sharper as the speed increases. 



The action of calcium on the phosphorescence of yttrium has 

 already been described. 



Yttrium and cerium. — Cerium has the effect of deadening the 

 brilliancy of the yttrium spectrum in proportion to the quantity 

 added. All the bands remain of their normal sharpness. 



Yttrium 5 per cent., copper <)^ per cent., phosphoresces very 

 feebly. 



Yttrium 90 per cent., didymitim 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 

 phosphoresce. The tube is either too full of gas to allow the 

 phosphorescence to be seen or it becomes non-conducting. 

 When the mixture is illuminated by the glowing gas the absorp- 

 tion-lines of didymium in 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, 

 didymiu n brings out the yttrium spectrum fairly, but the tube 

 soon becomes non-conducting. 



Yttrium S per cent. onA g.ucinum 95 per cent, gives a bright 

 phosphorescence, 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., jjliosphoresces faintly, 

 the lines being very indistinct. 



Yttrium 5 per cent., titanium <)^ per cent., acts like thoria, 

 and the tube becomes non-conducting. 



Yt'.rium 5 percent., tungsten 95 percent. — This phosphoresces 

 of a bright yellow colour, the spectrum is brilliant, but the lines 

 are not sharply defined. In the phosphoroscope the colour 

 becomes greenish, and the spectrum shows only the green lines 

 of Gi8. 



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

 is of a pale yellowish-white, and the spectrum is veiy brilliant, 

 being equal to that shown by 30 per cent, of yttrium with 

 barium, calcium, magnesium, or strontium. In the phosphoro- 

 ■icope the colour becomes reddish, and the Gj3 green line is the 

 first to come. No citron line is seen. If the yttrium contains 

 .1 trace of samarium, the samarium spectrum, which is scarcely 

 seen under ordinary circumstances, now coa;es out distinctly. 



Zinc sulphate mixed with 95 per cent, of calcium sulphate 

 phosphoresces a bright bluish-green colour ; the spectrum contains 

 no bands or lines. 



Zinc sulphide (Sidot's hexagonal blende, Comptes rendus, 

 vol. Ixii., 1886, pp. 999-lcoi ; vol. Ixiii., 18S6, pp. 18S-S9). — 

 This is the most brilliant phosphorescent body 1 have yet met 

 with. In the vacuum tube it begins to phosphoresce at an 

 exhaustion of several inches below 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 ci^stalline ma-s 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 

 constituents of yttrium is an additional proof, if confirmation be 

 needed, that the bodies I have provisionally called Go, Gj3, G5, 

 cSic. (Roy. Soc. Proc. vol. xl. 1SS6, p. 502), are separate 

 entities. It may be as well here to collect together the evi- 

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

 bodies seriatim : — 



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

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

 4S2. This earth occurs in different proportions in purified 

 yttria from different minerals. Saniarskite, gadolinite, hiel- 

 mite, raonazite, xenotime, euxenite, and arrhenite contain most 

 Go, whilst fluocerite and cerite contained notably less of this 

 constituent. The addition of lime brings out the phosphor- 

 escence in Go in advance of that of the other constituents. The 

 behaviour in the phosphoroscope of Go when mixed with the 

 alkaline earths also points to a difference between it and its 

 associates. With lime the blue phosphorescent band of Go 

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

 with a sm.all quantity of lime being Gj3, Ga, G5, and with a 

 large quantity of lime, G5, Go, G/3. Employing strontia 

 instead of lime, the order of appearance in the phosphoroscope 

 when the quantity of strontia is small is GS. Go, Gij, and when 

 the quantity of strontia is in excess, Go, G17, G|3. Baryta in 

 small quantity brings out the lines in the phosphoroscope in the 

 following order, GS, Go, GtIjI but when the baryta is in excess 

 the order is GS, Gr;, Go. The chemical position taken up by 

 Go in the fractionation scheme precludes it from being due to 

 the bodies I have called GS, G7, G^, GC, S7, or 85. It closely 

 accompanies GS (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. Go is not a separate entity, its 

 blue line must be due to the citron-b.and-forming body called 

 GS. The difference between Go and GS is brought out in a 

 marked manner by the phosphoroscope when baryta or strontia 

 is present ; the citron line of GS being entirely suppressed, while 

 the blue line of Go is brought out with enhanced brilliancy. For 

 these reasons I am inclined to regard Go as a separate body, 

 although the evidence in favour of this view is not so strong as 

 in the case of some of its other associates. 



GS. — -^n earth phosphorescing with green light, and showing 

 in the spectroscope a close pair of greenish-blue lines of a mean 

 wave-length of 545. This earth can be separated by chemical 

 fractionation from the other constituents of yttrium. It con- 

 centrates at the most basic end, and is present in the samarium 

 which invariably makes its appearance at this end of the frac- 

 tionation of yttrium. It is one of the prominent lines in Yo, 

 where also it accompanies some of the samarium lines. GS, 

 however, is not a constituent of samarium, for it is easy to 

 purify samariu m by chemical me<ans so that it does not show a 

 trace of the GS green lines, .-ilthough it is very difficult to get 

 GS free from some of the samarium lines. The residual phosphor- 

 escence of GS is very considerable, and its green lines show first 

 in the phosphoroscope when only yttrium is present. The addi- 

 tion of lime keeps back the glow of GS, and brings forward 

 that of GS. Strontium and barium act on GS very diflferently 

 to lime. A small quantity of strontium brings forward the 

 residual glow of GS, whilst in large quantities strontium keeps 

 the phosphorescence of GS back to the last. 



G7. — .\n earth phosphorescing with a green colour, and 

 showing in the spectroscope a green line having a w.ave-length 

 of 564. This is one of the least definite of all the supposed 

 new bodies. It appears to be a constituent of sa uarium, occur- 

 ring in the fractionation of yttrium among the most basic consti- 

 tuents connecting yttrium and samarium. Its point of maximum 

 intensity is, chemically, very well marked, and is at a different 

 part of the fractionation scheme to those of the other lines of 



