ARGON, A NEW CONSTITUENT OF THE ATMOSPHERE. ' 31 



The gas was furtlier circulated, until aljS(;i'[)ti(iii liail a[>paiciitly ceassed. This 

 took about 6 bours. Density was again determined. 



(e) 162.843 cubic centimetres, measured at 707.7 nun. (con-.) pi'essure and 

 15°.00 C, weighed 0.2773 gramme. Hence, 



Weight of 1 litre at o^ and 760 mm r . 7784 grammes. 



Density compared with hydrogen (O = 16) 1 9 . go 



(f) A second determination was carried out, without further circulation. 

 162.843 cubic centimetres, measui'ed at 769.0 uuii. (cdi'r.) [)ressure and 16°.00 



C, weighed 0.2773 gramme. Hence, 



Weight of I litre at 0° and 760 mm i . 7820 grammes. 



Density compared with hydrogen (O = 16) 19-94 



It is better to leave these results without comment at this point, and to return 

 to them later. 



11. Spectrum of Argon. 



Vacuum tubes wei'e filled with argon pi'epared by means of magnesium at 

 various stages in this work, and an examination of these tubes has been kindly 

 undertaken by Mr. Crookes, to whom we wish to ex)iress our cordial thanks for 

 the exhaustive study to which he has subjected its specti'um. The first tube \vas 

 filled with the early pieparatiou, of density 19.09, which obviously contained some 

 nitrogen. A photograph of its spectrum was taken, and compared with a photo- 

 graph of the spectrum of nitrogen ; and it was at once evident that a spectrum 

 different fi'om that of nitrogen had been I'egistered. 



The second specimen of argon submitted to examination was that of density 

 20.38. The light emitted from it is of a ci-imson color, with a blue or lilac shade. 

 The electrodes were of platinum. The s[)ectrum seen in this tube has nothing in 

 common with that of nitrogen, nor indeed, so far as we know, with that of any 

 known substance. But one peculiarity must be chronicled. When the current is 

 passed from the induction coil in one direction, that end of the capillary next the 

 positive pole appears of a I'edder, and that next the negative pole of a bluer hue. 

 An explanation of this phenomenon is probably to be found in a paper by Mr. 

 E. C. C. Baly,' in which he describes experiments on a mixture of two gases. One 

 of his final conclusions is : 



" That when an electric current is passed thiough a rarefied niixtui'e of two 

 gases, one is separated fi'om the other and appears in the negative glow." We 



' Proceldings of the Physical Society, 1893, p. 147. 



