L U M E 28, N O . 11, N O V E M B E R 1 9 5 6
1791
AY DIFFRACTION DATA
,I1Dimensions.
aa
= 8.62 A,, bo = 11.00 A,, co = 6.10
A.
irmula Weights per Cell. 4. Formula Weight. 105.14. Density. 1.211 grams per cc. (displacement), 1.211 grams per cc. (x-ray).
slowly without agitation over a period of several hours. Typical orystsls prepared in this manner are shown in Figures I and 2. The positions of the lead atoms in each of the polymorphic farms have been determined by Azaroff (1). Crystsk of Form I1 transform readily t o Form I in solution (Figure 3).
OPTICALPROPERTIES Refractive Indices (5893 A,, 25"C.), a
= 1.516, p = 1.528, 1.538. Optic Axial Angle. 2V = ( - ) 84"24' (calculated from a, 0,
y =
9"d " ) , _-_
O& Axial Plane. Perpendicular to 010 Acute Biseotrix. a. Extinction. a A e = 16" in itcute 8.
X-Ray Powder Diffraction Data d 6.81 5.33 5.12 4.83 4.65 4.30 4.08 3.75 3.43 3.37 3.26 3.14 2.98 2.90 2.73 2.66 2.57 2.46 2.41 2.39 2.35 2.23 2.04 1.990 1.905 1.850 1.795
hkl 110
1/Il 0.50 0.80 0.50 0.80 1.00
OIL
101 101 iii. 120
0.40 1.00 0.20 0.20 0.20
200 021
0.40 0.20 0.20 0.30 0.10 0.10
211 03_1
0.10b 0.20 0.10 0.10
12i
211 220
131 221 112
.
3oi . 23i.202 311 20! 141
d (Calod.! 6.78 5.33 5.12 4.83 4.64.4.6)
4.30 4.08 3.75 3.44 3.39 3.26 3.14 2.98 2.90 2.73 2.66 2.58.2.56 2.47 2.42 2.43
0.05 0.05
melt does not crystallize on cooling.
I
P r i n c i d Lines d 5.37 5.01 4.84 4.64 4.44
1/11
4.27
6
4.13 3.90 3.78 3.29
8
3.20 3.15 3.08 3.02 2.95
a
5
4 10 4 1vu,. Beta Angle.
107.5'
