136 



THE ROYAL SOCIETY OF CANADA 



Professor J.J. Thomson^ has shown by positive ray analysis that 

 the argon atom may lose several electrons, and it was hoped that by 

 use of a high accelerating potential a third spectrum due to a highly 

 ionized type of atom might appear. However, with a voltage of 

 240 volts between the filament and the grid no new lines were brought 

 out. 



II. Description of Apparatus 



As there was no effort made to determine the resonance or 

 ionization potential a simple lamp of the three-electrode type was 

 used (see Fig. 1). The lamp made of Pyrex glass was cylindrical in 

 shape, 15 cm. long and 3.5 cm. in diameter. Two electrodes of 

 coarse tungsten wire were sealed in at one end and a 9 mil tungsten 

 filament F was silver soldered to these electrodes. The other end of 

 the lamp was closed by a quartz window securely sealed with wax. 

 The grid G consisted of two concentric cylinders of fine iron wire 

 gauze, having a mesh of 12 wires to the inch, the inner one being 

 supported by the outer by means of short lengths of iron wire which 

 were silver soldered to both. The inner gauze cylinder was about 

 1 . 5 cm. in diameter and the one end was closed by a circular iron 

 plate S. Thus when the grid was in position the plate 5 prevented 

 the light produced by the heated filament from reaching the slit of 

 the spectrograph. The third electrode, which was also of tungsten 

 wire, was sealed in the side of the lamp and silver soldered to the grid. 



£, 



+ t 



H2^-i 



=^^1 



yvvwwA- 



■WV\AA- 



■" G 



Fig. 1 



All metal parts were first heated to red heat and then cleaned 

 with acid. The lamp was then mounted in an electric furnace in 

 such a way that the quartz window dipped in a water bath which 



'Thomson, Rays of Positive Electricity, First Edition, p. 53. 



