laboratory by a n electrolytic process (1). It contained 0.07% neodymium and 0.003y0 europium (determined spectrophotometrically). No other rare earth elements were detectable spectrographically in the ytterbium oxide used, which was p u r s e d by ion exchange methods. The structure of these orthorhombic trifluorides, belonging to the space group Pnma - D:! with a unit cell containing four formula units, has been determined by Zalkin and Templeton (3). They reported the following unit cell dimen-
sions: YFs ao,
A.
bo, A. cn.A. Volume per formulaunit,A.a Density (x-ray), gramspercc.
SmFa
YbFs
Crossed polarized light
47.79 51.84 46.76 5.069 6.643 8.168
The powder x-ray diffraction pattern of yttrium fluoride is given on ASTM cards 50546, 5-0547, of samarium fluoride on card 5-0517, and of ytterbium fluoride on cards 5-0551, 5-0552. The density of the trifluorides crystallized from melts was determined with a Berman microbalance as 6.61 grams per cc. for the samarium salt; 8.17 grams per cc. for the ytterbium compound. CRYSTALMORPAOLOQY.The trifluorides crystallized from their melts as aggregates of coarse anhedrons cbaracteriaed by prominent (0101 cleavage and twinned polysynthetically on (101) (Figure 1).
157. 158.
Figure 1. Cleavage fragments of samarium trifluoride showing repea
6.353 6.669 6.216 6.850 7.059 6.786 4.393 4.405 4.434
OPTICALPROPERTIES. YF,
SmFa
1,536 1.553 1.569
1 , 577
YbF3
Refractive indices (5893
A.) n,
w nz
Geometric mean Molecuiar refraction,cc. Optic m i d sngle,2V
569 1.597 1.580 1.608 1.599
respect to the trace of the composition plane (1011. The angle between the Zdirections in adjacent twin hmellae ie 67" for samarium t d u o r i d e , 71" for ytterbium fluoride. Color. Samarium trifluoride is pink; yttrium and ytterbium fluorides Yare colorless. LITERATURE CITED
1.55% 1.594 1.58% 9.21
10.60 9.41
85'
72'
optic Orientation.
Z = a.
x = c;
(1) Onstott, E. I., J . Am. Chem. Sac. 77,
2129-32 (1955). (2) Zalkin, A,, Templeton, D. H., Ibid., 75, 2453-8 (1953).
78'
y
=
b;
Extinction Angles. Extinctions on (0101cleavage plates are symmetric with
WORK done under auspices of Atomic E~~~~ commission. Crystallographic data for pubhation in this section should be sent to W. C. McCrone, 500 East 33rd St., Chicago 16, Ill.
Lanthanum Trifluoride, LaF, Neodymium Trifluoride,
NdF,
EUGENE STARITZKY and L. 9. ASPREY, The University of California, Las Alamos Scientific Laboratory, Lor Alarnos, N. M.
anu nsouymiurn IIUIITKXS were precipitated with hydrofluoric acid from aqueous solutions of correspnnding chlorides. The precipitates were heated to 400' C. in an atmosphere of gaseous hydrogen fluoride, heated under vacuum to about 1000" C., and then melted under argon a t about 1400" C. The fluorides crystallized from their melts as coarse-grained anhedral aggregates. The lauthanum source material used was purified by ion exchange methods. Spectrographic analysis indicated the presence of O.O2y0 calcium aud 0.005y0 magnesium; no rare earth elements were LN'PHAN UM
L-
856
ANALYTICAL CHEMISTRY
aecemed. Spectrographic analysis of the neodymium salt indicated the presence of O.lyo magnesium, 0.01% calcium, 0.03rr/o iron, and 0.2y0 cerium. No other rare earth elements were detected. Oftedal (9) proposed a structure for hexagonal rare earth fluorides belonging to the space group PG8/mcm - D ~ with B a cell containing six formula units. Cell dimensions reported by Oftedal (1) for lanthanum fluoride are, after converting from ICX to Angstrom units, aa = 7.117 zt 0.007 A,, co = 7.344 0.007 A.; for neodymium fluoride corresponding figures are a. = 7.035 i. 0.007 A., co = 7.210 5 0.007 A.
*
X-RAY DIFFRACTION DATA. LaFr Cell dimensions ao, A. eo,
A.
da,
NdFt
7.186 zt 7.030 f 0.001 0.001 7.352 zt 7.200 i 0.001 0.001 1.023 1.024
Volume per formula unit, A.8 54.80 Formula weight 195.92 Density, grams per CC. 5.936
51.36 201.27 6.506
The above cell dimensions were determined hy linear extrapolation against the function (eos%/sin8 Cos28/8) to the zero value of that func-
+
Table 1.
Partial Powder X-Ray Diffraction Patterns of Lanthanum Trifluoride and Neodymium Trifluoride
hk.1
00.2 11-0 11.1
20.0 11.2 20.2 12.1 30.0 11* 3 00.4 30.2 22.1 11.4 22.2
41.1 22.4 41.2 00.6
33.0 41.3 11a6
Lanthanum Fluoride d, A., d , A., calcd. obsd: 3.676 3.593 3.228 3.112 2.570 2.375 2.240 2.074 2.025 1.838 1.807 1.745 1.636
3.66 3.58 3.21
Neodymium Fluoride d, A., d, A., calcd. obsd.a
Ih
2.236 2.070 2.020 1.834 1.803 1.741 1.632
3.600 3.515 3.159 3.044 2.515 2.324 2. i92 2.029 1.982 1.800 1.768 1.707 1.602
3.58 3.49 3.14 3.03 2,515 2.310 2. is9 2.022 1.974 1.795 1.764 1.703 1.600
50 15 95 < 5 10 < 5 5 65 100
1.614
1 610
1 579
i
577
5
1.335 1.2847 1.2739 1.2253 1.1977 1.1878 1.1597
1.283 1,273 1.224 1,197 1.187 1.159
1.2575 1.2464 1.2000 1.1717 1.1623 1.1356
1.255 1 245 1.199 1.171 1.161 1.134
2: 562
I
15
50 35 10
< 5 10 10 15 30 10
More than 20 additional lines 17-eremeasured in each pattern.
Philips 114.6-mm.-diameter powder camera, Straumanis mounting; X(CuKa) = 1.5418 A. * Relative peak intensities above background from densitometer measurements. Intensities of Ianthanum trifluoride pattern were not significantly different.
Table II. Absorption Spectrum of Neodymium Trifluoride
(Band maxima in mp and relative intensities as viewed with a Zeiss microspectrometer eyepiece) Parallel to E Parallel t o 0 ... 667 medium ... 628 very weak 595 very weak 595 weak 582 medium strong 586 weak 578 very strong (578 very strong 570 medium strong 532 weak 524 mediiim 524 weak 521 strong 521 very strong 518 medium strong 512 weak 513 meditim weak 505 medium weak 509 weak 470 weak 470 \leak
iii zitm
tion of a. and co values calculated from several groups of diffraction lines in restricted angular ranges I n all some 30 cy1 and cy; lines in the angular range 40' to 84' were used in each case.
OPTICAL PROPERTIES. Uniaxial negative. Refractive indices (5893 A , ) no %E
Geometric mean Lorente-Lorenz refraction, cc. Color
LaFa
SdF,
1.603 1.597 1.601
1.628 1 621 1.625;
11.31 10 95 Colorless Brown
The above figures for molecular refraction have been plotted as a function of the atomic number of the metal on Figure 1, together with corresponding data for the orthorhombic trifluorides of samarium and ytterbium. This property of trifluorides of lanthanide elements appears to be approximated by a linear function of the atomic number, not markedly affected by structural differences. LITERATURE CITED
(1) Oftedal, I., 2.phys. Chem. (B) 5 , 272I
9
57
Figure 1 . fluorides
de
J9 $0 611
&h
ATOMIC
6Ci h d8
64 65 NUMBER
91 (1929). (2) Ibid.,(B) 13, 190-200 (1931).
d9 7'0 7\
Molecular refraction of some rare earth tri-
~ O R Kdone under auspices of Atomic Energy Commission. Crystallographic data for publication in this section should be sent to W.C. -MMcCrone, 500 East 33rd St.. Chicago 16, Ill.
Society for Analytical Chemistry of the Society for AnalytA ical Chemistry was held November MEETING
7 in London, at which the following paper waa presented and discussed. Structure of Dithizone and Its Metal Complexes. H. M. N. H. IRVING, In-
organic Chemistry Laboratories, South Parks Road, Oxford. Diphenylthiocarbazone (dithizone, I and 11, X = SH) was first prepared by Emil Fischer in 1878, but i t was not introduced into analysis until 30 years ago. About this time, and on the basis of exiguous experimental evidence, struc-
tural formulas were ascribed to a number of the metal dithizonates, and Helmuth Fischer postulated that the imino-hydrogen of I could be replaced to form the so-called keto complexes-e.g., 111-and that the hydrogen of the thiol form, 11, X = SH, could in certain circumstances be removed also to give enol complexese.g., IV. VOL. 2 9 , NO. 5, M A Y 1957
a
857
