[ 704 ] 



LXVII. Note on the Diffusion of Neon through Hot Quartz. 

 By 0. W. BlCHABDSON, Professor of Physics, and R. 

 C Ditto, Fellow in Physics, Princeton University *. 



IN the course of some experiments which were undertaken 

 to try to detect the presence of the heavier inert gases 

 (xenon, krypton, argon, and neon) in minerals, we have 

 observed that neon diffuses through red-hot quartz tubes. 

 The possession of a similar property by helium has been 

 known for some time, and appears to have been observed first 

 by A. Jacquerod and F. L. Perrot f. 



The method originally adopted consisted in heating the 

 mineral in a closed silica-ware tube, initiallv exhausted. 

 After the heating, the gas evolved was drawn off into a large 

 exhausted reservoir. It was subsequently compressed into 

 another heated quartz tube containing metallic calcium. Both 

 the calcium and the mineral were heated to a temperature of 

 about 1000° 0. After exposure to the hot calcium, the gas 

 was forced into a narrow capillary tube, where its spectrum 

 could be examined by means of a Hilger wave-length 

 spectroscope. Our experience is that hot calcium absorbs 

 all the chemically active gases completely except hydrogen. 

 We tried different temperatures between 800° C. and l200° 0., 

 but always found that the calcium hydrogen compound exerted 

 a dissociation pressure which, though minute, was large enough 

 to be troublesome. We could not use higher temperatures 

 on account of the silica-ware tubes becoming soft and 

 collapsing "under the atmospheric pressure. The hydrogen 

 contamination was got rid of by forcing the gas into a small 

 tube provided with a platinum tube heated by an electric 

 current. The hydrogen diffused out through the hot platinum 

 and burnt in the air of the room. These processes were gone 

 through until we got a good clean spectrum showing the 

 mercury lines and the lines of the inert gases present. As 

 a rule the primary hydrogen lines were also visible, but not 

 always. 



The presence of neon in our apparatus was first noticed 

 when a specimen of witherite from Northumberland, England, 

 had been heated for a long time. We subsequently succeeded 

 in proving that this mineral did not give off neon, and then 

 tried the experiment with a new silica-ware tube which did 

 not contain, and never had contained any foreign substance. 

 After the exhausted tube had been heated for about one hour 

 the gas was drawn off and examined. It was found to give 



* Communicated by the Authors. 



t Comptes IZendus, cxxxix. p. 789 (1904). 



