1-5 



Conductivity of Metals and their Vapours. 603 



= =4xl0 6 ohms. It cannot be considered certain 



4x10- 



that the current really passed altogether through the vapour. 

 Quartz conducts appreciably at such temperatures, especially 

 if it contains the slightest trace of alkali. 



A special experiment was made in which a current was 

 sent through the hot quartz by means of wires passed up the 

 limbs of the tube, in the absence of mercury. This experi- 

 ment showed that the conduction through the quartz was 

 comparatively insignificant. 



TTe have, then, as the resistance of the liquid, in the 

 tube, about *25 ohm, and for that of the vapour, not less 

 than 4 x 10 6 ohms. 



The liquid resistance is therefore, at a full red heat ; still 

 10 7 times that of the saturated vapour. 



A few experiments were made on arsenic vapour. The 

 procedure was very similar to that adopted in the case of 

 mercury. The inverted Y-tube had, however, to be filled in 

 a special manner ; this was as follows. 



The two branches were sealed at the ends. The finely 

 powdered arsenic was introduced through a (fig. 2) and 



Tlr 



ZJUU^ 



shaken down till it filled the side limbs, a was then sealed 

 also. The whole tube was heated so as to melt the arsenic, 

 under pressure. On cooling, the metal solidified in an 



2R 2 



