1072 



Tliiy can easily be explained. In the high vaonnm the Na,0 is 

 very volatile on a moderate rise of the temperatni-e, so that it is 

 vaporized from the incandescent wire, before it has had time to 

 react to an observable degree. The activity of the Na,0 (K^O) in 

 the ghiss is due to the fact that Na,0 (K,0) when solved in the 

 glass can act on the tungsten in the evacnated space at a mnch 

 higher temperature than would be possible with the free oxide 

 because of its volatility. 



This is analogous to what is known of the KH SO^ wiiich, used 

 in analytic cliemistr}', is so much more active than SO,, because at 

 high temperatures the SO, in the KH SO^ can still be active in the 

 condensed state. 



Doubtlessly however the tungsten acts also on the Na^O when the temperature 

 is so low, that this substance is hardly distilled. This has been mentioned in 

 the literature (comp. Gmelin-Kraut, Handbuch etc.) and moreover we- have stated 

 it by experiments. P. Lenard (1. c p. 201) already has shown that in the oxidi- 

 zing pari of the BuNSEN flame a metal like platinum is rapidly attacked by oxides 

 and hydroxides of the alkalines, further also by carbonates and sulfates of the 

 alkalines. 



(t. Conclusions. 



By these experiments we have obtained sufKicient data to under- 

 stand, wliy glass can replace the action of phosphoius. 



Partly this is due to the fact that by the fractional distil- 

 lation, substances (alcali-oxides), are formed in extremely line particles 

 (vapoui's), which are able e.g. to tix traces of humidity. But 

 moreover free alkali metal is formed. This is ver}' important; 

 for when for the fii-st time the lamp is burned more or less 

 strong electric discharges take place, as was mentioned already 

 above. Now, the alcali metals are very active, but especially 

 when] electric discharges are sent through the lamp. G. Gehlhoff') 

 has shown namely that the application of the action of alcali 

 metals in glow-discharges forms one of the quickest methods for the 

 preparation of pure rare gases. 



Conclnsion: In the form of glass a substance vei'y inactive at loom- 

 temperature is introduced into the lanip, from which at high tem- 

 peratures, however, the free alcali metal is developed as a vapour, 

 and under the influence of electric discharges this can cause the 



1) G. Gehlhoff, Verb. d. Deut&ch, Phys. Ges. 13, 271 (1911). 



