﻿222 Dr. F. H. Newman on Absorption of Hydrogen 



and test for any chemical compounds formed, a modified form 

 of the apparatus was used, as shown in fig. 2. 



Pure hydrogen could b.j admitted to the discharge-tube A 

 in small volumes by manipulation of the taps 1\ and T 2 . 

 Two strips of platinum foil, about 10 cms. long, were sealed 

 in the tube E. These strips fitted closely to the glass 

 surface. A potential difference of 600 volts was applied 

 between these strips by means of small accumulators. In 

 this way the ions actually present in E were removed while 

 the discharge was proceeding in A. The tube E communi- 

 cated with a mercury cut-off K, and a U tube immersed in an 

 enclosure maintained at —40° C. Sodium-potassium alloy 

 was prepared in D, and after the whole of the apparatus had 

 been evacuated, the alloy was run into C. In this way a 

 bright and clean* surface was obtained on the alloy in C. A 



n \ HYDROGEN 



small volume of hydrogen was then admitted to A, the 

 mercury cut-off preventing the gas from entering C and D. 

 While the electric discharge was passing in A, the hydrogen 

 was allowed to enter C by manipulation of the cut-off. 

 Admitting successive volumes of hydrogen into A in this 

 way, and each time allowing communication with C while 

 the discharge was proceeding, an increasing amount of active 

 gas entered C, and an effect was observed on the surface of 

 the alloy. At first it appeared to be covered with a thin 

 white crystalline compound when observed through a 

 microscope. This white layer slowly changed, on the 

 admission of more active gas, to a dark grey-coloured 

 deposit. To show that this surface effect was not due to 

 impurities in the hydrogen, previous experiments were 

 made, the gas being admitted to C without the electric 

 discharge proceeding. There were no surface effects then, 



