PoLLOK — The Vacuum Tube Spec Ira of some Metals. 267 



identified ; but there was only one line belonging to the spark spectrum of 

 potassium, the double line X\ 4047-4, 40i4-3, but this line showed quite 

 strongly ; the spectrum is not reproduced, as it will be further investigated. 

 The metal rendered the capillary portion of the tube opaque, and could 

 not be photographed. 



Prh/cipal Liiiea of Potassium. 



SoDlTIM. 



Sodium chloride gives its spectrum with great ease and brilliancy in the 

 vacuum tube, the luminescence being of an intense yellow colour. The 

 metal was very easily volatilized, but rendered the capillary portion of the 

 vacuum tube opaque, so that I failed to obtain a photograph of its spectrum. 

 The spectrum of sodium chloride is not reproduced in the plate, but most of 

 the lines are seen in the spectrum of lithium chloride, owing to a small 

 amount of sodium present as an impurity. The introduction of the Leyden 

 jar made practically no change in tlie spectrum of this element. 



