Crystalline Structure of Antimony and Bismuth. 
79 
The intensities of the first three orders were observed to be 100 : 17 : 
0, while calculation gives 100 : 20 : 3. 
(d) (110) and (111) planes: 
James and Tunstall examined the spectra from these planes and found 
that they agreed with this arrangement. 
The spacings of the planes have been determined by the relative inten- 
sities of the spectra from the (111) planes ; hence the determinations of these 
intensities are of importance. The ratios were found to be 30 : 100 : 33 : 
4 : 12, while James and Tunstall found 60 : 100 : 48 : 0 : 15, giving a 
phase difference of 140° between the two sets cf planes. We found a phase 
difference of 148°. 
The spacings of the planes are given in Fig. 1. Fig. 2 shows the 
arrangement of the atoms on one of the eight small cells into which the 
rhombohedron can be divided. 
The shortest distance between atomic centres is 2 92 x 10~ 8 cm. 
Bismuth. 
Bismuth, like antimony, crystallises in the dihexagonal alternating system 
(calcite class). The three edges of the rhombohedron meet in the trigonal 
axis and the angle between any two of the edges is 87 0, 34'. The angle 
between the faces (10')) and (111) is 56°'24'. 
Again using an X-ray bulb with a palladium anticathode the glancing 
angles for the first order spectra were — 
(ill) (100) 
4°-18' 5°-8' 
Taking the density of bismuth 9 80 grm./cm. 3 we find that the unit 
rhomb contains 8 atoms and that the length of the side of unit rhomb is 
6 52 x 10- 8 cm. 
Assuming the structure of crystalline bismuth to be similar to that of 
antimony we find the spacings of one set of planes to be — 
Planes. 
r A ~ 21 
(100) (110) (111) (110) (111) 
Spacings 3-25 235 3-92 225 3-69 
The spacings are given in Angstrom units (10 -8 cm.) The relative 
positions of the two sets of planes have not been accurately determined. 
The intensities of the spectra from the (111) face showed much the same 
order as those from the corresponding face of antimony but were much 
fainter. 
Experiments are in progress for the measurement of these intensities 
whereby the second set of planes may be fixed. 
University of Capetown, 
February, 1921. 
