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On the unit cell of γ-UO3
N otes
2065
TABLE I.--RAMAN SPECTRA OF Xe()F4 Assignment
Pure
Liquid*
v9 ~,~ v~ ~'8
161 231 286 364
(vw) (w) (vw) (mw)
v:,
530
(s)
r~
566
ra-v ~
~,,
HF
Soln(0-78 M)
Same Soln ~ H20
Remarks Doubtful
(vs)
233 293 375 420 530 542 572
(~-l)t (1.5) (6.0) (4'5) (5.0) (9.0) (19-0)
818
(w)
735 820
(2-5) (<1)
919
(s)
927 1380
~255 (~-~0.5) 291) (1) 380 (1.5) 420 (1)
(5) (1)
540 (1-25) 572 (2-7-3-5) 740 (1) 850-860
(Several scans at varying conditions) With a wide slit there was some evidence for a band in this region
930 (1) 1380 (0-3)
* Pure liquid based on reports of SMITH et al., CLAASSENet al., etc. summarized in H. H. Science IV. Y. 145, 775 (1964). Cf. also Reference 1. ~ ( ) Intensity Arbitrary Scale.
HYMAN,
from hydrogen fluoride to guarantee that this precipitate did not contain xenon dioxide difluoride at least as a contaminant. The electrical conductivity of the hydrogen fluoride sample was 3 × 10-L The addition of XeOF4 decreased this somewhat (presumably due to reaction with impurities responsible for the conductivity). The conductivity increased slightly on the addition of water, but since the principal conducting species are still most likely impurities, no correlation with the chemistry of XeOF4 seems possible. It does not appear to be possible to prepare massive amounts of XeOaF~ by a controlled hydrolysis either in the gas phase or in a hydrogen fluoride solution. The existence of XeO~F~ as a rather short lived intermediate or unstable insoluble solid is fully compatible with the necessary rather slow time scale of this experiment. H . H . SELIG C/wmistr)' Division Ar~,onne National Laborator), A~gonne, Illinois
L . A . QUARTERMAN H . H . HYMAN
J. inorg, nucl. Chcm,. 1966. Vol. 28, pp. 2065 to 2066. Pergamon Press Ltd. Printed in Northern Ireland
On the unit cell of y-UO 3. (Received 10 March 1966) THE SYMMETRYand cell dimensions of Mallinckrodt or 7-UOa have been studied by a number of observers. PERlOII) deduced an orthorhombic cell with a -- 12.98, b ~ 10.70 and c : 7.49 kX, while DAWSON et al. <2~ reported sin2 0 and line intensity values for the phase and suggested monoclitlic * Based on work performed under the auspices of the U.S. Atomic Energy Commission. ~l) p. PEP,tO, Bull. Soc. chim. Ft. 776 (1953). ,2, j. K. DAWSON, E. WAIT, K. ALCOCK and D. R. CmLTON, J. chem. Soc. 3531 (1956).
2066
Notes
symmetry. CONNOLL¥(3) obtained a monoclinic cell with a = 13-05, b = 15"45, c = 6.89/~ and aft= 89'63 °. DEWOLFE~4) then re-interpreted CONNOLLV'S data in terms of an orthorhombic cell with 9.70, b = 9.80 and c = 19'92 A, ot'a pseudocell with a = b = 6'90, c = 19-92 A and y ~ 90-57 °. ENGMANN and DEWOLEE~5~subsequently reported improved cell constants based on their own measurements and also presented a structure for ~-UO3 based on the pseudo cell but with space group I41/amd. BEKETOV et aL ~8~have suggested that two different forms of y-UO3 may exist, one of which is obtained by thermal decomposition of uranyl nitrate (DAWSON, BEKETOV), and the other by oxidation of U3Os at high oxygen pressures (CONNOLLY). This suggestion cannot be accepted for several reasons: (1) DAWSON et al. state that "anhydrous UO3 samples obtained by thermal decomposition of uranyl nitrate, UO3.2H~O, or UO3.0'8H20 are crystallographically indistinguishable • • • from the product of oxidation of lower uranium oxides with 130 atm of oxygen at 700°." (2) ENGMANN and oEWOLrF arrived at an identical indexing for a sample prepared from UOz(NOa)2.6H20 at 400-600°C in air as from the CONNOLLY sample prepared by the alternative method. We have recently succeeded in growing single crystals of 7-UOa from a ZnCI~ melt. A mixture of ),-UO8 and anhydrous ZnCI2 was heated for several weeks in sealed silica tubes at ~625°C. Some reaction (to form ZnU3010) occurred, but the major portion of the UO3 was recovered as crystals measuring up to 1'0 mm in diameter. Although these crystals exhibit a pronounced polysynthetic twinning, they can be indexed on the basis of the orthorhombic symmetry assigned by DEWOLFF. A comparison of his values with our single crystal measurements is given in Table 1.
TABLE 1
oEWoI_rF Present study
a(A)
Orthorhombic b(A)
9-70 9.71 4- 0.01
9'80 9.77 4- 0.01
c(A) 19"94 19.92 4- 0.02
a = b(A) 6.89 6.88
Pseudo-cell c(A) 19.94 19.92
y 90'34 ° 90'31 °
Our studies on numerous samples of y-UOs prepared by all methods listed lead us to conclude that only one form of y-UO3 exists. Minor differences in number of diffraction lines observed and in line intensities can be ascribed to variations in crystallinity and sample purity.
Chemistry Division Argonne National Laboratory Argonne lllinois t3~ D. (4) p. 15) R. (6~ A.
H. HOEKSTRA S. SIEGEL E. GEBERT
E. CONNOLLY,Acta Crystallogr. 12, 949 (1959). M. DEWOLFF, Avta Crystallogr. 14, 322 (1961). ENGMANN and P. M. DEWOLFE,Acta Crystallogr. 16, 993 (1963). R. BEKETOV,V. N. STREKALOVSKIIand V. G. VLASOV,J. Struct. Chem. 6, 150 (1965) (Translation).
2065
TABLE I.--RAMAN SPECTRA OF Xe()F4 Assignment
Pure
Liquid*
v9 ~,~ v~ ~'8
161 231 286 364
(vw) (w) (vw) (mw)
v:,
530
(s)
r~
566
ra-v ~
~,,
HF
Soln(0-78 M)
Same Soln ~ H20
Remarks Doubtful
(vs)
233 293 375 420 530 542 572
(~-l)t (1.5) (6.0) (4'5) (5.0) (9.0) (19-0)
818
(w)
735 820
(2-5) (<1)
919
(s)
927 1380
~255 (~-~0.5) 291) (1) 380 (1.5) 420 (1)
(5) (1)
540 (1-25) 572 (2-7-3-5) 740 (1) 850-860
(Several scans at varying conditions) With a wide slit there was some evidence for a band in this region
930 (1) 1380 (0-3)
* Pure liquid based on reports of SMITH et al., CLAASSENet al., etc. summarized in H. H. Science IV. Y. 145, 775 (1964). Cf. also Reference 1. ~ ( ) Intensity Arbitrary Scale.
HYMAN,
from hydrogen fluoride to guarantee that this precipitate did not contain xenon dioxide difluoride at least as a contaminant. The electrical conductivity of the hydrogen fluoride sample was 3 × 10-L The addition of XeOF4 decreased this somewhat (presumably due to reaction with impurities responsible for the conductivity). The conductivity increased slightly on the addition of water, but since the principal conducting species are still most likely impurities, no correlation with the chemistry of XeOF4 seems possible. It does not appear to be possible to prepare massive amounts of XeOaF~ by a controlled hydrolysis either in the gas phase or in a hydrogen fluoride solution. The existence of XeO~F~ as a rather short lived intermediate or unstable insoluble solid is fully compatible with the necessary rather slow time scale of this experiment. H . H . SELIG C/wmistr)' Division Ar~,onne National Laborator), A~gonne, Illinois
L . A . QUARTERMAN H . H . HYMAN
J. inorg, nucl. Chcm,. 1966. Vol. 28, pp. 2065 to 2066. Pergamon Press Ltd. Printed in Northern Ireland
On the unit cell of y-UO 3. (Received 10 March 1966) THE SYMMETRYand cell dimensions of Mallinckrodt or 7-UOa have been studied by a number of observers. PERlOII) deduced an orthorhombic cell with a -- 12.98, b ~ 10.70 and c : 7.49 kX, while DAWSON et al. <2~ reported sin2 0 and line intensity values for the phase and suggested monoclitlic * Based on work performed under the auspices of the U.S. Atomic Energy Commission. ~l) p. PEP,tO, Bull. Soc. chim. Ft. 776 (1953). ,2, j. K. DAWSON, E. WAIT, K. ALCOCK and D. R. CmLTON, J. chem. Soc. 3531 (1956).
2066
Notes
symmetry. CONNOLL¥(3) obtained a monoclinic cell with a = 13-05, b = 15"45, c = 6.89/~ and aft= 89'63 °. DEWOLFE~4) then re-interpreted CONNOLLV'S data in terms of an orthorhombic cell with 9.70, b = 9.80 and c = 19'92 A, ot'a pseudocell with a = b = 6'90, c = 19-92 A and y ~ 90-57 °. ENGMANN and DEWOLEE~5~subsequently reported improved cell constants based on their own measurements and also presented a structure for ~-UO3 based on the pseudo cell but with space group I41/amd. BEKETOV et aL ~8~have suggested that two different forms of y-UO3 may exist, one of which is obtained by thermal decomposition of uranyl nitrate (DAWSON, BEKETOV), and the other by oxidation of U3Os at high oxygen pressures (CONNOLLY). This suggestion cannot be accepted for several reasons: (1) DAWSON et al. state that "anhydrous UO3 samples obtained by thermal decomposition of uranyl nitrate, UO3.2H~O, or UO3.0'8H20 are crystallographically indistinguishable • • • from the product of oxidation of lower uranium oxides with 130 atm of oxygen at 700°." (2) ENGMANN and oEWOLrF arrived at an identical indexing for a sample prepared from UOz(NOa)2.6H20 at 400-600°C in air as from the CONNOLLY sample prepared by the alternative method. We have recently succeeded in growing single crystals of 7-UOa from a ZnCI~ melt. A mixture of ),-UO8 and anhydrous ZnCI2 was heated for several weeks in sealed silica tubes at ~625°C. Some reaction (to form ZnU3010) occurred, but the major portion of the UO3 was recovered as crystals measuring up to 1'0 mm in diameter. Although these crystals exhibit a pronounced polysynthetic twinning, they can be indexed on the basis of the orthorhombic symmetry assigned by DEWOLFF. A comparison of his values with our single crystal measurements is given in Table 1.
TABLE 1
oEWoI_rF Present study
a(A)
Orthorhombic b(A)
9-70 9.71 4- 0.01
9'80 9.77 4- 0.01
c(A) 19"94 19.92 4- 0.02
a = b(A) 6.89 6.88
Pseudo-cell c(A) 19.94 19.92
y 90'34 ° 90'31 °
Our studies on numerous samples of y-UOs prepared by all methods listed lead us to conclude that only one form of y-UO3 exists. Minor differences in number of diffraction lines observed and in line intensities can be ascribed to variations in crystallinity and sample purity.
Chemistry Division Argonne National Laboratory Argonne lllinois t3~ D. (4) p. 15) R. (6~ A.
H. HOEKSTRA S. SIEGEL E. GEBERT
E. CONNOLLY,Acta Crystallogr. 12, 949 (1959). M. DEWOLFF, Avta Crystallogr. 14, 322 (1961). ENGMANN and P. M. DEWOLFE,Acta Crystallogr. 16, 993 (1963). R. BEKETOV,V. N. STREKALOVSKIIand V. G. VLASOV,J. Struct. Chem. 6, 150 (1965) (Translation).