Results of Crystal Analysis. 



07 



For a given lattice we can, as shown by W. H. and 

 W. L. Bragg, calculate the glancing angle (0) when we 

 know the density (p) of the crystal, the atomic weight (A), 

 and the wave-length (\) of the X-rays. 



Fig. 1. 



. ^ 



A 





Gold (III) 



A . 



/*° 



IS° 



16° 



30° 3f° 



A lead (Hi) 



A A 



12° 



13° 





*v° ts e 



Settingangle of chamber 



Let the side of the elementary cube be a, and the number 

 of atoms associated with a cube of side a be n, then 



a 6 = 



/?A 



(1) 



where N is the number of atoms in a gram-atom (N 

 61-5 X10 22 ). V 



Let the spacing of the (111) planes be 



d m = ea, 

 then \ 



ea 



.6? 



(2) 



where 6 X is the glancing angle of the first order. 

 From (1) and (2) we get 



. a 1 X 3 /cN 



F 2 



