The Homogeneity of Helium. 



323 



different sets of vibrations, each complete in itself, and each resem- 

 bling the other in general form. Yet it must be acknowledged that 

 our experiments have not disproved the existence of two gases in 

 heiium of approximately the same density ; in fact it may be contended 

 that helium is a pair of elements like nickel and cobalt. 



We are disappointed in the result of this long research, because we 

 had thought it not improbable that an element of density 10 and 

 atomic weight 20 might prove to be the cause of the fact that different 

 samples of helium possess different densities, according to the mineral 

 from which they are extracted, and also of the separation of helium 

 into portions of different densities by diffusion. We still regard it 

 as by no means improbable that further research will lead to the dis- 

 covery of the " missing " element, and this appears to be a fitting 

 opportunity of stating our reasons for the belief. 



The difference between the atomic weights of helium and argon is 

 40 — 4 = 36. Now, there are several cases of such a difference. If 

 we compare the groups of which the first members are fluorine, 

 oxygen, nitrogen, carbon, boron, beryllium, and lithium, we obtain 

 the following table : 



Fluorine 



Chlorine 



Manganese 



Oxygen 



Sulphur 



Chromium 



Nitrogen 



Phosphorus 



Vanadium 



Carbon . . . . , 



Silicon 



Titanium 



The elements helium and argon have been given a provisional 

 place. 



The differences between the extreme members of these small groups 

 are given in the short table which follows : — ■ 



Manganese— Fluorine ... . 36'0 Chromium— Oxygen 36 3 



Vanadium — Nitrogen 37'4 Titanium — Carbon 36*1 



Scandium — Boron 33*1 Calcium — Beryllium 31*0 



Potassium — Lithium 33*1 Argon — Helium ........ 36'0 



The difference between the atomic weights of argon and helium, it 



At. wt. At. wt. 



19-0 * Boron 11-0 



35-5 L ^ Aluminium 27"0 



55-0 195 Scandium 441 171 



32-0 LbU Magnesium 24"3 ^ 



52-3 203 Calcium 40'1 15 * 8 



14-0 Lithium..... 7-0 



31-0 l 70 Sodium 23-0 160 



51-4 ZU4 Potassium 391 151 



13-0 - Helium 4-0 . 



28-3 ] 6 * ? 20-0 160 



48-1 19 ' 8 Argon 40-0 20 '° 



