On the Companions of Argon. 439 



(new), was next determined. A bulb of 32'35 cubic cm. capacity 

 was filled with this sample of neon at 612*4 mm. pressure, and at a 

 temperature of 19'92 it weighed 0'03184 gram. 



Density of neon 14'67. 



This number approaches to what we had hoped to obtain. In 

 order to bring neon into its position in the periodic table, a density 

 of 10 or 11 is required. Assuming the density of argon to be 20, 

 and that of pure neon 10, the sample contains 53*3 per cent, of the 

 new gas. If the density of neon be taken as 11, there is 59'2 per 

 cent, present in the sample. The fact that the density has decreased 

 from 17*2 to 14* 7 shows that there is a considerable likelihood that 

 the gas can be farther purified by fraction ation.* 



That this gas is a new one is sufficiently proved, not merely by the 

 novelty of its spectrum and by its low density, but also by its beha- 

 viour in a vacuum-tube. Unlike helium, argon, and krypton, it is 

 rapidly absorbed by the red-hot aluminium electrodes of a vacuum- 

 tube, and the appearance of the tube changes, as pressure falls, from 

 fiery red to a most brilliant orange, which is seen in no other gas. 



We now come to the gas obtained by the volatilisation of the white 

 solid which remained after the liquid argon had boiled away. 



When introduced into a vacuum-tube it showed a very complex 

 spectrum, totally differing from that of argon, while resembling it in 

 general character. With low dispersion it appeared to be a banded 

 spectrum, but with a grating, single bright lines appear, about equi- 

 distant throughout the spectrum, the intermediate space being filled 

 with many dim, yet well-defined lines. Mr. Baly has measured the 

 bright lines, with the following results. The nearest argon lines, a& 

 measured by Mr. Crookes, are placed in brackets : 



Reds very feeble, not measured. 



First green band, first bright line 5632 '5 (5651 : 5619) 



second 5583 '0 (5619 : 5567) 



third 5537-0 (5557:5320) 



Second green band, first bright line . . . 5163 '0 (5165) 



second .... 5126 '5 (5165 : 5065) brilliant. 



First blue band, first bright line 4733 '5 (4879) 



second 4711 '5 (4701) 



Second blue band, first bright line 4604 -5 (4629 : 4594) 



Third blue band (first order) 4314 -0 (4333 : 4300) 



Fourth blue band (second order) 4213 "5 (4251 : 4201) 



Fifth blue band (first order), about .... 3878 (3904 : 3835) 



The red pair of argon lines were faintly visible in the spectrum. 

 The density of this gas was determined with the following 



* June 16th. After fractionation of the neon, the density of the lightest sample 

 had decreased to 137. 



