790 



Mr. Ivar Maimer on the 



The greatest difficulties have been to get the bulb suffi- 

 ciently hard, several of the elements examined having a low 

 melting-point, and, therefore, a comparatively high-vapour 

 tension, even at not very high temperatures. Consequently 

 an effective arrangement of cooling had to be used for all the 

 elements examined except Mo, Ru, Pd, and Ag, the anti- 

 cathode being cooled with a stream of cold water (fig. 2). 



Thanks to this arrangement the bulb could be kept rather 

 hard even with an anticathode of indium with a melting- 

 point of less than 200°. Yet it was necessary to use an 

 intermittent primary current closed for about a second and 

 then interrupted for the same space of time, &c. In this 

 way the bulb could, as a rule, be worked with for hours with- 

 out softening. The pump (a Gaede mercury pump) then 

 was working incessantly, cooling with charcoal in carbonic 

 acid and ether also always being used. 



The fusible elements (Cd, In, and Sn) were melted on the 

 anticathode, the metals more difficult of fusion were either 

 tied with a platinum wire or soldered on to the anticathode. 

 Some difficulties were caused by Y, Zr, Ba ; La, and Ce, 

 which were used in form of oxides. A good method of 

 fastening them proved to be the making of a thick cream of 

 the oxide and waterglass, which was then, as a thin layer, 

 cemented on a rifled anticathode. If the layer was too 

 thick, the heat easily caused splinters to be burst away and 

 fall on the cathode, which instantly weakened the bulb. 



The results are to be seen in the following Table. 



