A N A L Y T I C A L CHEMISTRY
420 Partial Powder X-Ray Diffraction Pattern of Potassium Silver Dicyanide
a
h kl
d, A., Calcd.
d, A,, 0bsd.4
00.2 10.0 10.1, 10.: 10.2,10,2 00.4 10.3, 10.3 11.0 10.4, 10.5 11.2 20.0 20.1, 2 0 . : 10.5, 10.5 20.2,20.2 00.6 11.4
8.795 6.408 6.021 5.179 4,397 4.326 3.700 3.626 3,410 3.204 3.152 3.084 3.011 2.932 2.831
8 81 6.35 6.00 5.17 4.39 4.30 3.68
25 5 40 15 30 15
3.40
40
3.13 3.07 3.00 2.92
100 10 16
2.811
60
...
..
...
...
I j
20.3. 2 0 . 2 10.6, 10.5 20.4, 20.4 12.0 12.1, 12.: 20.5.20.5 10.7. 10.5
2.666 2.590 2,422 2.400 2.369 2.339'
12.2, 12.2 11.6 12.3, 1 2 . 3 00,8
2.335 2.298 2.239 2,199
2.812
i
J
2.583
I/Iib
3
,.
J
5
... ...
.. ..
2.362
20
2.331
J
2.291 2.235 2.191
10 5 10
Philips 114.6-mm.-dianieter powder caalera, Straumanis mounting;
X(CuKa) ,= 1.5418 A .
Relative peak intensities above background f r o m densitometer measurements. b
{loo) with { l g z ) ,(loo] a i t h 1111) and (nil,or (2nt a i t h the two bases. Polar Angles. (111) A (100) = 67" 18'; (100) .i (101) = 106' 2' (106' 3' calculated) X-RAYDIFFR.4CTIOS DATA Space Group. Hoard ( 3 )determined the structure of this compound assuming the space group to be P3c ( D f d ) . As noted above, morphological development of some crystals was noncentrosymmetric, indicating the space group to be P3c (Ctv). No piezoelectric effect could be detected, however, with an instrument of the Giebe-Scheibe type. Cell Dimensions. Within limits of experimental error cell dimensions determined were in agreement with those given by Hoard ( 3 ) : a = 7.40 A., c = 17.59 -4.;cell volume 834 A.3 Formula Weights per Unit Cell. 6. Formula Weight. 199.01. Density. 2.38 gram per cc. (x-ray); 2.376 (flotation). OPTICALPROPERTIES Uniaxial positive. Refractive indices (minimum deviation method). Length, Microns 0.664
Na 0.5893 H g 0.5461 H g 0.4358
Molecular Refraction
Geom%ean
n0
ng
1.485 1.4915 1.4969 1.5233
1.599 1.6035 1.6078 1.6244
25.55 25.79 26.00 26.93
1.522 1.5279 1.5330 1.5563
Colorless. LITERATURE CITED
rhombohedral combinations of 1100) and (TOO), with or without the bases, and assumed a centrosymmetric class and space group. However, several combinations of forms without a center of symmetry have been observed with great frequency, such as
(1) Bassett, H., Corbet, -1. S., J . Chem. SOC.125, 1660-75 (1921). (2) Groth, P., "Chemische Krystallographie," vol. I, p. 318, Engelmann, Leipeig, 1906. (3) Hoard, J. L.. 2. Krist. (A) 84, 231-56 (1933). WORKdone under the auspices of the Atomic Energy Commission
107. Potassium Gold Dicyanide, KAu(CN), EUGENE STARITZKY and FINLEY H.ELLINGER, The University of California, Los Alamor Scientific Laboratory, Los Alamor, N. M. gold dicyanide was prepared by evaporating a t P room temperature an aqueous solution of potassium cyanide and gold cyanide in equimolar proportion. According t o
Refractive Indices
OTASSIUM
Bassett and Corbet ( I ) this is the only double salt formed a t 25' C. in the system KCN-iluCPI'-H*O.
Wave Length, A,
Microns 0.664 S a 0.5893
Hg 0.5461
0.470 H g 0.4358
CRYSTAL MORPHOLOGY System and Class. Trigonal, trigonal pyramidal. ilxial Element. a = -13' 52'. Habit. Commonly pseudo-rhombohedral combinations of the trigonal p y r a m i d d 1 0 0 ) and (OOT), often with one or both basal pedions { 111}, 11111 . ?;once_n_trosymmetriccombinations of trigonal pyramids { 100 I and ( 122 1 vere also observed frequently. h-0 piezoelectric effect was observed. Polar Angles. (100) A(010) = 114' 46'; (100) (212) = 121" 49' (calculated 121' 48').
X-RAYDIFFRACTIOK DATA Space Group. R3 (Cs4). The structure of potassium gold dicyanide has been studied by D. T. Cromer, of this laboratory, who will describe it in a publication t o appear shortly. Cell Dimensions. a. = 9.74 A4.;01 = 43.9"; cell volume -103 rl.s Formula Keights per Cell. 3. Formula Weight. 288.33. Density. 3.56 grams per cc. (x-ray); 3.55 (pycnometer). OPTICAL PROPERTIES Uniaxial positive.
no 1.588 1.6005 1.6111 1.643 1.6672
nB 1 689
1.6943 1.6996 1.713 1.7219
Birefringence, no - n E 0.101 0.0938
0.0885 0.070 0.0547
no
- nE
6.58 6.28 6.17 6.72 7.97
Molecular Refraction, Cc. 28.46 28.83 29.1 30.0: 30.76
Colorless. Dispersion of Birefringence. Potassium gold dicyanide exhibits striking abnormal interference colors. I n white light a wedgeshaped fragment of this compound exhibits (in views other than along the optic axis) instead of t'he usual sequence of interference colors a sequence of purple, green, and white bands. These remain distinct up to t'he 15th or 20th order. This phenomenon is due to the unusual character of the dispersion of birefringence, which increases rapidly with the wave length, as may be seen from the above table and from the plot, on Figure 1. The figures for wave length divided by the birefringence given in the fifth column of the t,able are proportional to the thickness of the section which gives an interference band of a given order for light of t h a t w$ve length. This quantity has a minimum in the green a t 0.545 micron. For every wave length longer than this minimum (say, in the red) there \Till correspond a shorter wave length (in the blue), light of these two wave lengths giving an interference band for the same thickness of section. Only green light is transmitted where these t,wo bands coincide. Both red and blue light is transmitted wherever the thickness of the section corresponds t o a given multiple of the minimum. This gives rise to a purple band. I n the lower orders there is a range of thickness between a given
V O L U M E 28, NO. 3, M A R C H 1 9 5 6
42 1
108. Potassium Dicopper Tricyanide Monohyd rate, KCUAC N)3.H,0 DONALD 1. W A L K E R ' and E U G E N E STARITZKY, The University of California, Lor Alamor Scientific Laboratory, Lor Alamor, N. M.
w
u
-
1.66OTASSIUM
w 1.64-
sium cyanide is cooled in presence of excess solid copper cyanide. Stability relations of this compound in the system KCX-CuCNHzO are given by Bassett and Corbet ( 1 ) .
L
c
ya
1.62-
LL
w
CL
dicopper tricyanide monohydrate crystallizes when
P a saturated aqueous solution of copper cyanide and potas-
CRYSTAL ~IORPHOLOGY System and Class. Monoclinic, prismatic. Xxial Elements Calculated from Cell Dimensions. a : b : c = 1.484: 1: 0.912; p = 97.5'. Groth ( 2 ) lists axial elements for this compound which are incompatible with the above set of values but approximate the axial ratios and p determined for potassium
1.60-
6'o
O(45 OkO 055 h , WAVELENGTH IN
-(
0!60 0!65 MICRONS
Figure 1. Refringence and birefringence of potassium gold dicyanide as functions of wave length of light 100
C C
0 0
-
-
Partial Powder X-Ray Diffraction Pattern of Potassium Gold Cyanide hkl
d. A,, Calcd. 8.79 6.13
d, Obsd 8.72 6.10 5.67 4 53 4 38 4 03
5.69
ioi
210, 11'0 322
iii
200 333
4 56 4 39 4 04 3.G41 3,363 3,233 3.131 3,066
3.63
3.36 3.22 3.12
1
211. 211 432, 423
2.9-"9 2,920 j 2.844 2.803 2.706 2.432 2.417 2 374 2.345 2.282 i
422 310, 130
2.278 2.241
332 220 321, 312 31 1 433 33 1 201, 210
3.06
I / I Ib 10 5
4
2
1 1 5 2 8
3 07
10
2 92
2
Figure 1. Crystal of potassium dicopper tricyanide monohydrate
2.84
6
Orthographic projections on (100) and parallel to b
...
2.70
..
4
..
2:413 2.372 2,341
8 3
