204 Dr. Gladstone on some Recent Determinations 



the current, the tube showed an even phosphorescent light 

 throughout, with a very faint line of the most delicate striae, 

 very difficult to distinguish. The striae did not become any 

 plainer on carrying the exhaustion to a considerably higher 

 point. I think it may be safely assumed that a tube of per- 

 fectly pure hydrogen would not striate at all. 



From the foregoing results I think the following conclusions 

 may be drawn : — 



First, that when an electric current is passed through a 

 rarefied mixture of two gases, one is separated from the other 

 and appears in the negative glow. 



Second, that striae are caused by the separation of the two 

 gases, and do not occur in a single pure gas or vapour. 



XXY. Notes on some Recent Determinations of Molecular 

 Refraction and Dispersion. Bij J. H. Gladstone, D.Sc, 

 F.R.S* 



AMONG the various indices of refraction which have 

 been published by different observers of late years, there 

 are some which have led me to further studies bearing on 

 the general relation of this branch of Physics to Chemical 

 theory. The following notes relate to the new metallic ear- 

 bonyls, the metals indium and gallium, sulphur, and to liquefied 

 oxygen, nitrous oxide, and ethylene. 



I. Metallic Carbonyls. 



Messrs. Ludwig Mond and Nasini f determined the mole- 

 cular refraction of nickel tetracarbonyl for the red ray of 

 hydrogen (Hj as 57*7, and the specific dispersion between 

 the lines 7 and a of hydrogen as 0*03475, which will give a 

 molecular dispersion between those limits of 5*93. This 

 indicates a very great refraction and an enormous dispersion. 



Through the kindness of Mr. Mond I have been able to 

 determine the refraction of two specimens of iron penta- 

 carbonyl for several lines of the spectrum, with the following- 

 result. The second and third lines in the Table relate to the 

 same specimen, the latter representing measurements taken 

 in a very acute-angled prism, and under the most favourable 

 circumstances for seeing the more refractive rays ; nevertheless 

 the spectrum was cut off so suddenly about the bundle of 

 rays at G that I cannot be sure of the exact measurement, 

 but think it differs little from the line 7 of hyd rogen. 



* Communicated by the Physical Society: read Feb. 10, 1893. 

 t Lincei, Rendiconti, vii. 411. 



