Crystalline Structure of Antimony and Bismuth. 
77 
intensities 1 ' of a normal set of spectra to be 100 : 34 : 14 : 7 : 4, we have 
30_ = 100 1 + cos/3 
100 34 1 4- cos2/i' 
which gives j3 — 148° approximately. 
The distance between one set of (111) planes would be divided by 
another set of (111) planes in the ratio of 0'412 : 0*588. 
The calculated ratios of the intensities for this spacing are 30 : 100 : 
31 : 5 : 15, which is in close agreement with the observed ratios. 
too) 
3-0?- 
<- 
(no) 
- %-k<f. - - 
{111) 
- 3-76- 
(no) 
3 -15- 
Fig. 1. — Spacing's of planes in Angstrom units (10— 8 cm.). 
The spectra could be explained by a structure similar to that of the 
diamond but distorted along the trigonal axis,f one set of (111) planes 
dividing the distance between those belonging to the other in the ratio of 
about 3 : 2 instead of 3 : 1 as in the diamond. 
(b) (100) planes : 
To settle whether a structure similar to that of the diamond will fit the 
observed facts we must examine what this ratio would give for the spectra 
* James and Tunstall, * Phil. Mag./ S. 6, vol. 40, No. 236. 
t Sir W. H. Bragg- and Prof. W. L. Bragg arrived at this conclusion in 1914 : 
' X ray and Crystal Structure/ p. 227. 
-1-65 
. V--J-JT2 
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