11114] on The Production of Neon and Helium. 21 



or in the metals used as electrodes. In one way many of the experi- 

 ments were disappointing, for it was found that very often an 

 experiment that had yielded the gases, wlien it was repeated gave 

 none, but at the same time there were many positive experiments 

 where it was almost impossible that the gases were due to any leak in 

 the apparatus. 



Some of the more important experiments were as follows : to 

 prove that the gases were not occluded in the aluminium electrodes 

 used, the aluminium was both fused in vacuo and the gases evolved 

 tested ; aluminium was also dissolved and the hydrogen produced 

 examined : in both cases neither lieHum nor neon could be detected. 

 The glass used in making the experimental tubes was treated in the 

 same way and negative results obtained. Glass bulbs were evacuated 

 as far as possible by means of the mercury pump, and washed out 

 with pure gases, and then heated for hours almost to their softening 

 point, but no helium or neon leaked through from the outer air. 

 Large quantities of mercury were boiled in vacuo, but not a trace of 

 helium or neon was given off. In another experiment the tube was 

 entirely jacketed by another tube that was so far evacuated as not to 

 allow the electric spark to pass ; neon was found as usual in the inner 

 tube, but what was remarkable, helium with only a small amount of 

 neon was present in the gases in the outer tube. In another experi- 

 ment a large glass bulb was surrounded by a coil of wire and 

 a powerful electrodeless discharge used : helium was found inside 

 the l)ulb. Diiferent metals were used as electrodes, copper, silver, 

 platinum, iron, potassium, sodium, lithium, magnesium, uranium, etc.^ 

 and in nearly every case helium, or helium and neon, proved to be 

 present in the gases that were pumped off from the experimental 

 tube. A quartz mercury lamp that had been in use over 3000 hours 

 was found to contain a relatively large amount of helium and neon. 

 A special form of lamp was therefore constructed consisting of an 

 inverted U-tube made of quartz, the end dipping into mercury in two 

 large test tubes, so arranged that the level of the mercury at the top 

 of the U-tube could be raised and lowered. A side tube from the 

 top of the apparatus led to a pump so that the gases could be pumped 

 out and examined. This lamp was running for over two months, and 

 gave helium mixed with a small quantity of neon during the whole 

 period. For the first few weeks the top of the U-tube was surrounded 

 by the air, but for the rest of the time it was enclosed in a jacket 

 filled with water ; the reason for doing this was that quartz is 

 known to be pervious to helium and neon at high temperatures, i.e. 

 100<V C. 



The summary of all these experiments had been : helium and 

 neon did not come from the glass of the apparatus ; the electrodes 

 could not be made to give either of these gases by heating or by 

 dissolution, and as far as possible all leak of air into the apparatus 

 was excluded, yet in a very large number of experiments both helium 



