CHEMISTRY: G. L. WENDT 
519 
The active modification is unstable, and must be allowed to react 
with the oxidizing substance within three or four minutes of the time 
of its formation. Here again its properties are those to be expected 
from an ozone form. Passage of the gas through a tube immersed in 
liquid air destroys its activity either by condensing the active variety 
which thus has a boiling point very much higher than. that of ordinary 
hydrogen, or by causing its disintegration into ordinary H2. 
A molecule larger than H2 is indicated by various facts. The purest 
obtainable hydrogen contracts when under the influence of alpha rays. 
This has recently been confirmed by Lind,^ working with large quan- 
tities of radium emanation. Usher,^ working in Ramsay's Laboratory 
in 1909, observed the same effect, but attributed the loss of volume to 
the projection of hydrogen molecules into the glass walls of the retaining 
vessel when bombarded by alpha rays, although the volume of hydrogen 
lost was larger than the number of alpha rays would permit, and 
although he was also unable to regain an adequate volume of hydrogen 
when the glass walls were pulverized and heated. 
The second line of evidence results from Langmuir's^ preparation of 
an active form of hydrogen which is probably monoatomic. This hy- 
drogen is present in an electric light bulb when the filament is heated 
to a high temperature, and is undoubtedly a consequence of the dis- 
sociation of hydrogen molecules at the high temperature of the filament. 
When the pressure in the bulb is very low this atomic form of hydrogen 
forms a layer on the inner surface of the glass wall, and although thus 
attached, is chemically active. It reacts rapidly with phosphorus vapor, 
for instance. It has two marked characteristics which distinguish it 
from the ozone form; namely, that it will not pass through a plug of 
glass wool, being adsorbed strongly by this substance; and secondly, 
that it does not exist except at the very highest vacua. When more 
hydrogen is admitted into the bulb than is necessary to make a layer 
one atom deep on the glass wall, the amount of active hydrogen is much 
reduced, the excess molecules seeming to react with the active atoms. 
The ozone form of hydrogen, on the other hand, will pass through long 
layers of glass wool and exists for some time at atmospheric pressure. 
The third and direct evidence that this hydrogen is polyatomic is 
found in the work of Sir J. J. Thomson and of Dempster,^ both of whom 
made use of the method of positive ray analysis to determine the con- 
stituents of a gaseous mixture in the presence of an electric discharge 
at high vacuum. The photographic method of Thomson and the 
electrical measurement method of Dempster both show the presence of 
