ANALYTICAL CHEMISTRY
1056 OPTICALPROPERTIES Uniaxial positive. Refractive Indices (5893 A.). no = 1.965 =k 0.005; no 2.08; geometric mean 2.00. Molecular refraction 31.2 cc. Color, 0 = olive green; E = brownish green.
=
Axial Elements. u : c = 1:0.902 (derived from unit cell dimensions). Habit. Dipyramidal { 101), often with subordinate { O O l 1. X-RAY DIFFRACTION DATA The structure of uranium tetrachloride has been determined by Mooney ( 1 ) . T h e space group is I 4 / u m d (D::). Cell Dimensions. uo = 8.298 =k 0.001 A , ; co = i.486 =t0.001 A. Cell volume 515.5 A? Mooney reported an = 8.296 =t 0.009 A.; co = 7.487 =t0.009 ,4. Formula Weights per Cell. 4. Formula Weight. 379.90. Density. 4.894 grams per cc. (x-ray).
Absorption Spectrum (Band maxima, mp, and relative intensities a s viewed with a Zeiss prism microspectrometric eyepiece) 0 E 680 medium .. 668 weak 668 weak 660 weak 660 weak 649 very strong 634 very strong 628 medium 618 strong }GO3 medium strong !OO weak 597 weak 5'92 strong 592 medium strong 590 weak .. ,582 weak 573 strong wide 573 medium strong, wide ,565 medium weak 565 mecjiuin weak 552 medium weak 553 medium weak 548 strong, wide 543 strong, wide 541 strong, wide 531 strong, \vide 5ii strong, wide 521 strong, wide 521 medium 514 weak ;OS medium strong 508 medium v e a k 505 weak 505 medium
OPTICALPROPERTIES Uniaxial, negative. Refractive Indices (5893 ii.). no = 2.03; n E = 1.92; geometric mean 1.993. Molecular refraction 38.6 cc. Color. 0 = greenish yellow; E = green.
Absorption Spectrum (Absorption maxima and relative intensity of bands as viewed in a Zeiss prism microspectrometer eyepiece) E 0 685 strong 6i0 strong 1 665 very strong 655 medium strong/ 645 medium strong 640 medium weak 608 very strong 608 medium 577 medium 558 medium strong 563 medium 518 strong (very wide) 518 medium weak 495 medium weak 495 medium strong (wide) 483 medium weak 483 medium (wide)
L I T E R 4 T U R E CITED
(1) Zschsriasen, R . €I., Acta Cryst. 1, 265-9 (1948). WORKdone under the auspices of the Atomic Energy Commission.
LITERATURE CITED
(1) Mooney, R. C . L., Acta Cryst. 2, 189-91 (1949).
127. Uranium Tetrachloride, UCI,
WORKdone under the auspices of the Atomic Energy Commission,
EUGENE STARITZKY, The University of California, Loo Alarnos Scientific Laboratory, Los Alarnos, N. M.
128. Uranium Trifluoride, UF,
may be prepared by halogenation U uraniumtetrachloride trichloride with chlorine at 2.50" C. RAKIUM
of
The University of California, Los Alarnos Scientific Laboratory, Los Alarnos, N. M.
CRYSTAL MORPHOLOQY System and Class.
EUGENE STARITZKY and R. M. DOUGLASS
Tetragonal, ditetragonal-dipyramidnl.
~ H E D R A Lcrystals
of uranium trifluoride were prepared by
-4.W. Savage of this laboratory by heating a mixture of uranium tetrafluoride and uranium metal a t 1050" C. in a hydro1.
Partial Powder X-Ray Diffraction Pattern of Uranium Tetrachloride hkl 101
200 211 112 220 202
301
103 321 312 400 213 411 004 420 303 402 332 204 323 422 501, 431 224 413
d, A., C alcd. .5,558
4.149 3.32.:3 , 15.3, 2,9338 2.7792 2,5946 2,3896 2,1998 2.148G 2.0745' 2.0707? 1.9436 1.8715 1.8555 1,8528) 1.8144 1.733.5 1,7060 1,6918 1.6624
d. A., Obsd." R ,53 4.12 3 30 3.14
2.92 2.77 2.38
2.38.5 2.191 2.137 2,064 1.039 1.862 1.847
:
1 730 1.703 1.090
1/1 h IO0 4 r, 35 J0 10 20 70 65 45 85 50
25 50
35
..
30 29
..
1 ' 620 30 1.8778 1 570 25 1,5665 1.662 20 314 1,523 1,5237 ? .I21 1,6092 1.504 512 25 1.4924 1.489 105 1,4734 1.467 10 1 ,4669} 440 a Philips 114.6-mm.-diameter powder camera, Straumanis mounting.: h(CuKrr) = 1.5418 A . b Relative peak intensities (above background) from densitometer measurements.
I , 13203
gen atmosphere for 2 hours. A crystal structure for rare earth trifluorides, belonging to the noncentrosymmetrical space group P6322 (D:), was proposed by Oftedal ( 2 ) from Laue and powder x-ray diffraction data for the mineral tysonite, (Ce, La,. . . ) F a . From oscillation photographs and piezoelectric tests (results negative) made later, Oftedal (3) proposed a revised structure belonging to centrosymmetrical space group P63/mon (I)&). Both of these structures are based on a unit cell with ao = 7.138, co = 7.295 A. (for tysonite), containing six formular units. As pointed out by Oftedal (2, 3 ) for rare earth trifluorides, and confirmed and extended t o isomorphous actinide trifluorides by Zachariasen (5),powder data from these phases are explicable in terms of a smaller cell containing two formular units, with a0 equal to 1/43 times that of Oftedal's structures, the a axes of the two cells lying a t 30 degrees to one another in the plane normal to the c axis. Thus for uranium trifluoride Zachariasen gave, from poivder data only, ao = 4.146 i= 0.003 A., co = 7.348 f 0.004 A, space group P6s/minc (D&), and cell content 2UF3. As discussed by Wyckoff ( 4 ) , Oftedal's revised structure has atoms in special positions of P6a/mcm with only t x o parameters in the equatorial zone unfixed by symmetry: for tysonite, z (metal atom in position g) = ca. 0.34 and z (fluorine atom in position k ) = ca. 2/3. If these two parameters were exactly 1/3 and 2/3, respectively, this arrangement would reduce to a simpler
1057
V O L U M E 2 8 , N O . 6, J U N E 1 9 5 6
scale.” In the present study no morphological, x-ray, or optical evidence of tn-inning was noted.
Partial Powder X-Ray Diffraction Pattern hkl”
002 100
101
102 110 103 004 112 200 201 104
20%
203 114 105
d , x., Calcd. 3.672 3.589 3.226 2.567 2.072.5 2.0227 1,8362 1.8049 1.7948 1.7435 1,6348 1,6124 1.4475 1.3744 1.3590
d, A., Obsd. b 3.67 3.58 3.21 2.56 2.069 2.022 1.834 1.803 1.796 1.741 1.633 1.611 1.447 1.374 1.359
I/IiC 60 30 100 20 60 90 20 60
15
40 15 10 30 35 35
X-RAYDIFFRACTIOS DATA Diffraction Symbol. 6/i~zinmP-c-. Oftedal’s structure bel,ongs to space group PBs/mcni. Cell Dimensions. a0 = d ( 4 . 1 4 5 ) = 7.179 A,; c g = 7.345 A , ,
all +0.001 11.;c / a = 1.023. Cell volume 3(109.3) = 327.0 A 3 Transformation ILatrix for Hexamolecular Cell in Termr of Dimolecular Cell. 110/120/001. Formula Weights per Cell. 3 ( 2 ) = 6. Formula Weight. 295.07. Density. 8.965 grams per cc. (calculated from authors’ cell dimensions; weight of unit atomic weight, 1.6602 X IO-*‘ gram).
OPTICALPROPERTIES
(29 additional indexable lines observed) Indices refer t o dimolecular pseudocell. b Philips 114.6-mm.-diameter powder camera, Straumanis mounting: X(CuKcr) = 1.5418A. c Relative ueak intensities above background from densitometer measurements
Uniaxial positive. Refractive Indices 15893 A , ) . no = 1.732 ZIC 0.002. R P = 1.738 ZIC 0.003; geometric nidan 11734. Molecular r e h t i o r i 13.2 cc. Color. 0 reddish violet, E brownish violet.
a
one based on the smaller cell indicated b y powder data, spare group P6r/mmc. Keissenberg, precession, and powder photographs obtained in the present study, using customary exposure times, indicate the smaller, dimolecular cell. However, long-exposure oscillation photographs from a crystal rotated about a n a axis of the dimolecular cell (normal to a n u axis of Oftedal’s hexamolecular cell) show tn-o faint layer lines intercalated between each pair of intense layer lines. T h e intense layer lines correspond to a strong pseudo identity distance of 4.145 A,, the faint layer lines to a true i[lentity distance of 3(4.145 A , ) = 12.435 A,, thus confirming Oftedal’s cell. [According to Katz and Rabinowitch ( I ) , “Oftedal stated t h a t t h e true unit cell, as determined by Laue photographs, is orthorhombic. . .” T h e source of this idea is not clear. “In agreement with this view, British Forkers found by goniometric measurements t h a t the crystals of UFa are probably orthorhombic.” An orthorhombic form of rare earth trifluorides hits been described by Zalkin ( 6 ) . ] CRYSTAL blORPHOLOGY
Only anhedral crystals were obtained. Twinning. Katz and Rabinowitch (1) state t h a t “all thcz crystals seem t o exist as triplrts, t,winne:d on a sntimirroscopic-
Absorption Spectrum (Band maxima in millimicrons and relative intensities a s viewed in a Zeiss prism iiiicrospectronietric eyepiece) Parallel t o 0 Parallel to E fi55 weak 652 strong 652 very strong 642 weak 030 medium weak 830 strong 018 weak 619 medium weak 612 medium weak, wide 590-609 medium s t r o n e 392 medium strong, wide 372 medium weak .5?2 medium strong 558 medium strong .lo8 medium weak 539 weak 528 medium weak, wide 528 medium weak 510 medium strong 510 medium strong, wide 493 strong, wide 493 medium strong, wide I
LITERATURE CITED
Katz, J. J., Rabinowitch, E., “Chemistry of Uranium. Part I. The Element, Its Binary and Related Compounds” ( S X E S VIII-5). n. 353. 3IrGran~-Hill.Sew York. 1951. Oftedal, I.,.Z.p h y s . Chem. B5, 272-91 (1929). I b i d . , B13, 190-200 (1931). Wyckoff, R. IT.G., “Crystal Structures,” vol. I, chap. V, p. 21 table pp. 17c, 23a, Interscience, New York, 1951. Zachariasen, W. H., Acta Crust. 2, 388-90 (1949). Zalkin, A., Tenrpleton, D. IT., J . Am. Chem. SOC.75, 2453-8 (1953). WORKdone under the auspices of t h e Atomic Energy Commission. Contribntions of crystallographic d a t a for this section should he sent to TTn1ti.i C . X r r r o n e , 3140 Suiitli Ilichignn Ave., Chicago 10, Ill.
MEETING REPORTS
Research Methods and Instrumentation SYMPOSIUM on Recent Developments in Research Methods
A and Instrumentation was held a t the Xational Institutes of
Health, Bethesda, N d . , May 14 to 16, in conjunction with the Sixth Annual Research Equipment Exhibit. T h e following papers were presented.
Use of the optical diffractometer [A. W. Hanson, H. Lipson. C. A. Taylor, Proc. Roy. SOC.AZ18, 371 (1953)] permits direct a n d detailed comparisons of the diffraction patterns of given models wit 11 the observed x-ray diffraction patterns. This study of optical transforms will be employed at several different levels of resolution. It can be employed to establish the molecular shape and orientation. t o recognize the presence and establish the orientation of regions of regular polypeptide chain configuration in the molecule, and to study the detailed molecular stereochemistry. The correlation of these and other studies was described.
Protein Structure by Physical Methods Approach to the X-Ray Crystal Structure Study of Proteins. BARBARA W. Low, Harvard University, Cambridge, Mass.
Amino Acid Composition of Tropomyosins from Various Animal National Institutes of Health. Sources. K. LAKIAND D. R. KOMISZ, Bethesda, Md.
The complete structural formulas of the insulins of beef, sheep, and pig have been established by Sanger and his associates. The x-ray crystal structure study of this protein is based on the correlation of several interrelated procedures. These include an extensive organic chemical study of a series of “heavy-atom” reagents in which the heavy atoms are attached at known specific sites in the molecule. Scale model studies of the insulin molecule have been carried out.
The amino acid composition of tropomyosins isolated from variouanimals was determined by using the Moore and Stein ion exchange chromatographic technique supplemented with other metho(l-. Tropomyosins from human uterus, calf heart, rabbit skeletal and uterus muscles, carp muscle, lobster, earthworm, and flatworni exhibited the characteristic uneven amino acid distribution first found in rabbit tropomyosin. Nevertheless, there is a noticeable
