167. Potassium Uranyl Vanadate, KU02V04 MARiA J. de ABELEDO, MARiA R. d e BENYACAR, and ROBERTO POLJAK Comisian Nacional d e Energ ' Atbmica, Buenos Aires, Argentina
uranyl vanadate (synthetic anhydrous carnotite) was prepared by melting a mixture of ammonium uranate with twice the stoichiometric amount of potassium vanadate; the technique was fundamentally that OTASSIUM
Table I, Partial Powder X-Ray d, A. hkl d, A. (Calcd.)a (Obsd.)b (6) 6.32 5.04 4.15 3.702 120 3.48 3.281 112 3.196 200 3.19 3.128 013 3.103 113 3.08 122 3.060 202 3.060 2.974 2.700 211 2.689 031 2.69 2.597 113 2.59 229 2.553 2.542 213 2.533 2.474 222 2.464 0;;) 2.465 2.451 2.444 2.155 2.132 2.130 $ ,( 2.142 2.124 (311) 2.064 2.0211 115 2.020 2.018) 213 1.996 140 1.982 1.979 313 1.966 015 042 1.939 1.935 311 1.933 124 1.922 322 1.900 1.902 320 1.886 215 1.810 302 1.824 1.809) 142 1.770 312 1.765 1.766 115 1.764 234 1.754 240 1.685 005 1.670 135 1.669 1,675 233 1.669 206
(;A)
proposed by Canneri and Pestelli ( I ) . After cooling, beautiful yellow plates up to 3 mm. long were obtained. CRYSTAL MoRPHoLoGY
To facilitate the comparison, the set-
Diffraction Patterns of Synthetic Anhydrous Carnotite d, A. hkl d, A, (Calcd.)a (Obsd.)b I C I C (6) 1.654 vs 315 1.653 vw (016) 1.649 333 MW MW 1.646 1.643 402 MW 1.640 1.640 S 1.621 331 I.621 (151) M 313 M 1.603 1.598 400 1.577 152 W 1.576 1.576 413 1.556 226 W 1.530 422 1.532 VW 1.530) 404 S 1.501 1.498 411 MW 340 420 335 vw VW 1.477 126 W 1.454 1.434 vw 1.430 153 1.422 vw 1.416 415 1.409 M 333 1.408 154 vw vw 1,393 1.392 433 1.381 324 W 1.367 vw vw 1.343 W W 1.317 153 413 vw 1.294 MS 1.280 519 1.277 vw 1.278 435 vw 1.264 M 1.259 522 vw 1.249 VW 1.238 W 1.224 vw 1.224 I.223 1,223 vw 1.210 1.193 532 256 533 MW 1.176 362 1.175 452 1.174 (118) 1.174 (451) From values of lo4sin2 B (6). 100-mm. diameter powder camera, (CoK,)A = 1.7902 A. Observed visually.
ting chosen by Sundberg and Sillen (6) has been conserved through the text, although the authors think it preferable to interchange axes a and c-that is, to adopt the setting used by Donnay and Donnay (2). System and class. Monoclinic, prismatic (6) Axial elements. a:b:c = 0.784:1:1.24 [derived from unit cell dimensions (6)I.
w;)
w
(:g)
0
b c
452
ANALYTICAL CHEMISTRY
;:%)
(,g)
;:
i C
Figure 1. Orthographic projection of crystal of potassium uranyl vanadate
Habit. Rhomboidal lates flattened { loo}, bounded by { 0117. The smaller crystals appear less elongated (Figure 2). The thickness of several plates was determined both on the microscope and by measuring the shadow cast by the crystal after shadow-casting with aluminum (Figure 3). Values ranging from 25 to 70 microns was obtained. Many plates were about 30 microns thick. Cleavage. !100} perfect; (001) prominent. ' Interfacial angles. 011 A 011 = 78" (observed optically and measured on electron micrographs). Beta angle. 104.2' (6).
X-RAYAND ELECTRON DIFFRACTION DATA The structure of anhydrous potassium uranyl vanadate has been determined by Sundberg and Sillen (6) on crystals obtained by a technique somewhat dif-
ferent than that described by Canneri and Pestelli. They give the following values: Space group. C h Cell dimensions. a = 6.590 A,; b = 8.403A.; c = 10.430A. Volume of Unit Cell. 560.0 A. Formula units per cell. 4.
From single crystal photographs, Sundherg and Sill& conclude that “the diagonal axis coincides with the diagonal of the acute angles in the plate.” Of
single crystals were obtained in a threestage Philips electron microscope; gold was used for calibration. Those Kikuchi patterns show that the 2 axes lying in the plane of the plate cut at a n angle of 90’. The values obtained from measurements on the electron diffraction patterns are:
b = 8.45A,; e = 10.43A. Formula Weight. 424.12. Density. 5.03 (x-ray); 5.02 (pycnometer).
OPTICAL PROPERTIES Refractive Indices (5893 A,). fl = 1.98 (* 0.02); y = 2.10 (* 0.02) q/aF[calculated from measured density and specific refractive energies (4) using k = 0.340 for V a s as given by Jaffe (S)] 1.925; a, calculated from ’
;/mF=
i
1.71.
Molecular Refraction (based on measured density). 40.0. Optical Orientation. 2 = 6. X nearly vertical, makes an angle of 3” with the normal to the plate. Optic Sign. Negative. Optical Axial Angle (58938.). 49”. Dispersion. r < v. Color. Yellow. Pleochroism not observable. ACKNOWLEDGMENT
Figure 2. Crystals of potassium uranyl vanadate, KUOaVO,
The authors wish to acknowledge the help given by Edehnira Mortola with
Table II. Comparison of Partial Powder X-Ray Diffraction Patterns of Synthetic and Natural Carnotite Natural Carnotite (from Cerro Huemul-MendozaSynthetic AnhyR. Arg.) - drous Carnotite d, A. Z (eat.) d, A. Z (est.) 6.45 10 6.32 vs 5.41 Barely v k 5.04 0.5 5.04 vw 4.17 5 4.15 MW 3.506 6 MW 3.48 3.522 0.5 7 3.211 3.19 S 3.135 6 3.082 9 3.08 M 2.686 2 2.69 W 2.604 Barely via. 2.59 VW 2.540 4 2.533 MW 2.463 Barely vis. 2.464 VW 2.3GO Barely vis. 2.150 8 2.142 M 2.095 Barely vis. 2.064 VW 2.050 Barely vis. 2.021 5 W 2.020 3 1.992 1.977 1.979 W 3 1.934 10 MS 1.939 1.901 3 1.9m M 1.822 1.824 W 2 1.777 2 2 1.765 1.766 vw 1.734 0.5 1.695 0.5 1.675 MW 1.669 10 1.656 3 1.646 MW M 1.607 3 1.603 1.594 3 1.576 W 1.569 2 1.540 2 1.532 W 1.500 4 1.501 S VW 1.474 Barely vis. 1.477 1.454 XV 1.449 4 1.434 VW 1.425 2 1.422 VW (5) Sundherg, I., SillBn, L. C., Arkiu K m i 1, 337-51 (1949). (6) Tavora, E., Conselho Nrtcianal de Pesquisas, Ria de Ja-neiro, personal communication. CONT~ISUTIONS of crystellographic data for this aection should he sent to W. C. McCrone, 500 East 33rd St., Chicago 16, Ill.
Figure 3. Crystals of potassium uronyl vanadate, shadowed with aluminum Angle of shadowing, 10’
the other two axes, one, which they denote by e, lies also in the plane of the plak; the third, a, is at an angle to it. Rotation single crystal photographs indicate that in our crystal the diagonal axis lies in the plane of the plate and bisects the obtuse angle (Figure 1); another ~, e, lies also in the plane of the plate, and the third one, a, is at an angle to it. These results were confirmed in patterns obtained by the precession method (6). Electron diffraction photographs from
the work in the Fedorov stage, and by E. Tavora with the x-ray study by the precession method.
LITERATURE CITED
(1) Canneri, G.,Pestelli, v.,
chim
G ~ Z .
ihl. 54, 641 (1924). ( 2 ) Donnay, G.,Donnay, . I . D. H., Am. M i w a b g i a t 39, 323 (1954). (3) Jaffe, H.N., Zbid., 41, 757 (1956). (4)Lsrsen, E. S., Berman, H., U. 8. Geol. Survey, Bull. 848,31 (1934).
Potentiometric Determination of Amides in Acetic Anhydride -Correction I n the article on “Pot
