1366 
erystal, and for the relation between infra-red and ultra-violet 
frequencies, may be tested in a simple way in the case of lithium. 
In the case of an equally simple lattice set with atoms of a higher 
atomic number the problem will be more difficult to solve. Thus we 
hope to make out presently for lithium hydride, whether possibly 
negative hydrogen ions occur here’). 
The simplicity of these substances in contrast with more intricate 
compounds gives scope for hope that the result will be unequivocal. 
Moreover the said lithium compounds have the advantage that in 
using the method of DrByr and Scuerrer place and intensity of the 
lines are much less influenced by the absorption in the. rod than 
they are with heavier compounds. The latter, when results of rays 
of different wave-lengths [Kcy- and Kg,-rays] are recorded, may 
give rise to small changes in intensity relations even as far as 
reversing them if intensity is slightly differing. So it lately appeared 
to us with sodium bromate. 
2. Apparatus. A Rausch von Traubenberg-Debye tube with 
exchangeable anti-cathode was used, as described by Bir and Kouk- 
MEYER ?). The required high voltage direct current was obtained by 
rectifying transformed alternate current with a Snook. The radius of 
the camera used was 5.0 em, the dimensions of the diaphragms were 
the same as those described by Bist and KorkMerer. The sample 
was rotated by means of a clockwork. 
3.  Photograms. After being cleaned under paraffin-oil and 
washed with dry ether a rod of lithium, 1,5 to 2 mm. thick was 
covered with a thin protecting layer of paraffin, and fastened by 
means of a glass foot in the axis of the camera. Even after days 
the surface remained bright metallic and shiny. A Cr-anticathode 
was used. The exposure lasted + 12 hours with a mean current 
of + 12 mA. parallel spark between plate and point 3 cm. 
Then a film was made of a glass rod covered with paraffin 
to be able tuo eliminate the interference lines caused by these 
substances. 
4. Observations and calculation. 
In column 1 of Table I are recorded the distances on the film from 
the middle of the image to the interference lines, expressed in mm., and 
1) Compare Moers, Z. f. anorg. u. allg. Chemie 113, 179 (1920). 
*) These Proc. Vol. 21, p. 405. 
