354 



NATURE 



[February 7, 1895 



li»eljr low density and its molecular simplicity, might well be 

 expected to rat. k among the gases. And iis inniness, which 

 has siTggested its name, suffiiieiitly explains why il has not 

 pre»iouily been discovered as a constituent of compound 

 bodies. 



We would suggest for this element, assuming provisionally 

 that il is not a mixture, ihe s>mliol K. 



\Vc hive to lec 'id our ihanks to Messis. Gordon, Kellas, 

 and .Maitl.e«s, who have materially assisted us in the prosecu- 

 tion of this reseaich. 



ON THE SPECTRA OF ARGON.' 



Through the kindness of Lord Raylrigh and I'mf. Ramsay I 

 have been enabled to examine the ^pecuum o( ihis gas in a very 

 accuiale spectroscope, and also to lake photographs of itsSpectia 

 in a speciiograph fined with a complete quartz train. The 

 results are both ineresling and imporiani, and entirely 

 corroborate the Dmclusions arrived at by the discoverers of 

 argon. 



Argon resembles nitrogen in that it gives two distinct spectra 

 accoming to the strengih of the induction current employed. 

 But while the two spectra of nitiOgeii are different in character, 

 one showed fluted bands and the other sharp lines, ihe argon 

 spectra both consist of sharp lines. Ii i', however, very difficult 

 to get ar^ion so Iree from nitrogen that it will rot show ihe 

 nitrogen flmings superposed on its own special system of lines. 

 I have used argon prepared by Lord Rayleigh, Prof. Ramsay, 

 and mysel', and, however free it was supposed to be from 

 nitrogen, I could always detect the nitrogen hands in iis 

 spectrum. The*e, however, soon disappear when the induction 

 spark is passed through the tube for some time, varying from a 

 a few minutes lo a few hours. 



The pressure of argon givirig the greatest luminosity and most 

 brill ant spectrum is 3 mm. (The best i)ressure fir nitrogen is 

 75 or 80 mm.) .\\ this piint the colour i.f the discharge i^ an 

 orangeied, and the spectrum is rich in red rays, t«o beirg 

 espe. iaily prominent at wavelengths 696 56 and 70564. On 

 pa.ssing the current the traces of nitrogen hands soon disappear, 

 and the aigon speclium is seen in a slate of purity. 



II the prcs-ure is (urther reduced, and a Leyden jar inter- 

 calated in the circuit, ihe colour of the luminous discharge 

 changes from red 10 a rich sieel-blue, and the spectrum shows 

 an almost entirely dillerent set o( lines. The two spectra, 

 called for brevity red and blue, are shown on the large map, the 

 upper spectrum l>eiMg that of "blue " argon, and the lower one 

 that ol " red " argf>n. It is not easy 10 olitain the blue colour 

 and spectrum entirely free (rom the red. It appears that a low 

 eleclr motive force (Jem spark, or 27,600 volt-) is reqiii'ed to 

 bring out the red, and a high E. M.F. and a very hut >paik foi 

 the blue. The red glow is produced by the positive spark, and 

 the blue by the negative spaik. 



t have l^kcn photographs tjf the two spectra of argon partly 

 supeipo>ed. In ih s way their dissimilaiiiy is readily seen.-' 

 In the spectrum of the blue glow I hive counted 1 19 lines, and 

 in that ol the red glow So lines, u^aking 199 in all. Of these 

 26 appear to be common to Ito'h spectra. 



The di^apI)earance of ihe led glow anil the appearance of llie 

 blue glow in argon as the exhaustion increases also resembles 

 the dianpearance of ihe red line of hydrogen when exhaustion 

 is raised 10 a high point. 



I hjvc iiiepaic'i tulies containing other ga«es as well as nitro- 

 gen at ilifi'cien' pressures, and have examined their spectra both 

 tjjr eye obiervalions and by photogiaphy. The sharp line 

 spccnum ol nitrogen is not nearly so striking in brilliancy, 

 numlier or sharpness of lines as are those ('f argon, anrl ihe 

 most careful sciutiny fails lu show any connection between llie 

 spectra. I can detect no lines in common, lieiween the spectra 

 of argon and the band s|>ecirum o( nitrogen there arc two or 

 three clo^e apiToximations of lines, but a projection on the screen 

 ol a magnified image ol the two spccira p.irily super|)osed will 

 5hr>w that iwo at lea*t of these arc not really coincidences. 



1 have found no other speitium-uivint; gas or va oiir)ield 

 spectra at all 111 e those of argon, and the appU'cnt coincidences 

 in kome of Ihc line*, which on one or iwiroctasion^ are noticed, 

 have been very few, and would probably diiappear on using a 



I Abtlraci of a paper I,y Mr. William Cr'H)ke*, F.R.S. 

 3 Pii •to^rapti* of ihe difTwenl tpectra i,f argon, and other gaseou* *l»eviia 

 (or rovipa<tv>n, were projected on Ihe Kreeo. 



NO. ' ■? ly, VOL. 51 ) 



higher dispersion. Having once obtained a tube of argon 

 giving the I'Ure spectra, I can make no alteration in it, other 

 than what 1 have explained takes place on voijing the spaik or 

 increasing the exhausiion, when the iwosieitia change (rom 

 one t> the other. As far, therefore, as spectrum woik can de- 

 cide, the verdict mut, 1 think, be that Lord Rayleigh and Prof. 

 Ramsay have added one, if not two, members to the family of 

 elementary bodies. 



The Two Spectra of Argon. 

 [Lines having intensities below 8 have been omitted.] 



Blue. 



Red. 



The totals arc : — 



1 19 lines in the " blue " spectrum. 

 80 lines in the " red" spectrum. 



199 total lines. 

 26 lines common lo the two spectra. 



