Physics. — “Research by means of Röntgen Rays on the Structure 
of the Crystals of Lithium and Some of its Compounds with 
Light Elements”. 1. By J. M. Brsvorr and A. Karssen. (Com- 
municated by Prof. P. Zeeman). 
(Communicated at the meeting of March 26, 1921). 
(For some ten years the researches at the Laboratory for general 
and inorganic chemistry of this University have for the greater part 
been directed to the solid substance. With a view to extend the 
methods of research also to those that make use of Röntgen rays, 
hoping in this way finally to get more knowledge about the finer 
internal states of equilibrium, steps were taken to get the required 
Röntgen apparatus. 
Through the great kindness of the municipality and of the Amster- 
dam University Association we have now this institution at our 
disposal, and we feel obliged to express our hearty thanks to 
both bodies. 
The task we have set to leads us to the typical allotropic sub- 
stances, but first we wanted to examine some simple, but never- 
theless very interesting cases, in which results could be expected 
which are of importance for the knowledge of the nature of the 
link. For these cases were chosen Li and LiH, with the result 
described below. A. Smits]. 
I CITHIUME 
1. Introduction. The investigation of Li and some of its compounds 
with light elements is perhaps more suitable than many of the 
compounds examined hitherto for drawing conclusions concerning 
structure and binding of the particles on account of the small number 
of electrons outside the nucleus of the component atoms’). 
The notion e.g. that electrons and ions must be considered as 
equivalent elements of the space lattice, which view offers inter 
alia great advantages for the explanation of the structure of the 
1, Thus DeBYE and SCHERRER could show for LiF, that there are no atoms, 
but ions in the lattice-points. Physik. Zeitschr. 19, 474 (1918). 
