750 Dr. G. Borelins on the 



for a stable state and the geometrical properties of tbe 

 lattice. The condition is 



2e(<£ e -</>„) = min. or _(^_£ a ) = 0, . . (5) 



which gives, in combination with (2') and (2"), 



2b-b' = 2aB/l ~ 1 (6) 



The geometrical properties give approximately 



7/7 2xl2 6 «2- e ,-TN 



' : ' = H^72r : HR- 2 2 - • • • ^ 



For different symmetries of the outer electrons in the 

 atom, fx takes different values : 5, 9, or more. This will be 

 discussed further in the next paragraph. 



§ 5. Compressibility. 



Born and Lande, from their space-lattice theory, found 

 the compressibility at the absolute zero-point for salts of the 

 type NaCl to be given by 



- 9 / A + + A\* 



*"-'8.1-742e s (/4-l)\ N> /' 



where A + and A_ are the atomic weights of the ions. With 

 fju=9 they find good agreement with experimental results. 

 As the atom model of Bohr would lead to /u,= 5, they propose 

 a cubic symmetry of the outer electrons in the atom that 

 would, at least under certain condition's, give yu,= 9. Our 

 fundamental equations lead, in the way shown by Born and 

 Lande, to the same value for /x. Neglecting the weight of 

 the electrons besides that of the atoms, we may write 



*~"l-742eV-l [) 



From this equation I have calculated jul for the metals 

 that are known from X-ray analysis to have a symmetry 

 consistent with our premises, using values for k and p* 

 holding for ordinary temperatures, and have found 



On 7 



Ag 8-5 



Au 12 



Al 6-5 



Pb 75 



Ni (8) 



* Tables of Landolt-Bdrnstein-Roth. 



