1154 



property of the metal and is determined by the selective absorption 

 of the atoms. 



We should like to acknowledge tlie val able assistance rendered 

 by Mr. R. d'Hoi.landkr in helping us to prepare many of the elaborate 

 experiments. 



Delft, Anorg. and Physic. -chemical Laboratory 



of the Technical University. 

 Eindhoven, Lab. of Philips, ''Metal Filament Ijamps" Works Ltd. 



