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CRYSTALLINE STRUCTURE OF ANTIMONY AND BISMUTH. 
By A. Ogg. 
(With two Text-figures.) 
Antimony. 
Antimony crystallises in the dihexagonal alternating (calcite) class' of 
hexagonal crystals. The crystalline symmetry is that of a rhombohedron, 
the three edges which meet in the trigonal axis being the axes of the crystal. 
The angle between any two of these edges is 86°-58'. From the geometry of 
the rhomb it is easy to find that the angle between the planes (HI) 
and (110) is 37°-23' and that between the planes (100) and (111) is 56°'48\ 
If we take the sides of the rhomb to be a and suppose that an atom is 
placed at each of the corners of the rhomb, then the distances between the 
planes of atoms are — 
d l00 = -9973a (1) 
d m = -6071a (2) 
d ll0 = 7236a (3) 
d n() = -6881a (4) 
By means of an X-ray spectrometer, the bulb having a palladium anti- 
cathode, the glancing angles of the first order spectra were experimentally 
found to be — 
(100) (111) (110) 
5°-30' . 4°-30' . 7°-30 / 
Applying the formula nX = 2d sin 6, where n is the order of the spectrum, 
X = 0-584 x 10 — 8 cm., and 0 the observed glancing angle, we find — 
d m = 3-72 x 10- 8 cm. (5) 
d 100 = 3-05 x 10- 8 „ (6) 
d uo = 2-24 x 10- 8 „ (7) 
From (2) and (5) we find a — 6*12 X 10~ 8 cm. 
„ (1) „ (6) „ „ a = 3-06 x 10- 8 „ 
„ (3) „ (7) „ „ a = 3-09 x 10" 8 „ 
It is evident from the calculated values of a that the spacings between 
the (100) planes and also those between the (110) planes are half what we 
