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The reactions of lanthanide oxides and antimony oxides
J. inorg,nucl.Chem.,1970,Vol.32, pp. 681 to 686. PergamonPress. Printedin Great Britain
NOTES
The reactions of lanthanide oxides and antimony oxides (Received 9 June 1969)
INTRODUCTION Tins paper is concerned with the preparation of rare earth-antimony double oxides. A considerable amount of work has been done on rare earth-A~O3 systems[l], where A stands for trivalent metal ion, however no report has appeared on compounds of the rare earth oxides with antimony oxide. Behavior of antimony oxide at elevated temperatures is complicated. Antimony trioxide Sb20:, for instance, is oxidized to tetraoxide Sb..,O~ (which is double oxide between Sb._,O:~and Sb20~), which decomposes again to Sb203 at higher temperature [2]. There are three crystal systems in sesquioxides of the rare earths, including A-type (hexagonal), B-type (monoclinic) and C-type (cubic) as reported by Warshaw et a/.[3]. The present investigation was undertaken to see the relationships between reactions with antimony oxides and the crystal systems of rare earth oxides, especially lanthanum oxide, praseodymium oxide, neodymium oxide, gadolinium oxide and dysprosium oxide, in some detail. EXPERIMENTAL Rare earth oxides of 99.9 per cent purity (Lindsay Chemical Division, American Potash & Chemical Corporation) which had been pre-purified, were thoroughly mixed with antimony oxides (Sb.,O:~, Sb,,O4 or Sb~O.~) by grinding the fine powders together. Antimony trioxide and Sb=,O~ used were prepared by hydrolyses of SbCI.~ and SbCIs, respectively. Antimony tetraoxide was prepared by thermal decomposition of Sb20~. Each mixture was fired in an alumina crucible in open air for 2.5 hr at a fixed temperature, and then cooled in a furnace. X-ray diffraction patterns of the samples were obtained with a Rigaku Denki diffractometer "Geiger-flex" using Ni-filtered CuKt~ radiation at a scanning speed of 1° (2#)/min. X-ray fluorescent spectrographic analyses of rare earth elements and of antimony were made on a Rigaku Denki X-ray fluorescent spectrograph unit with scintillation counter (NaI:T1), tungsten target X-ray tube and lithium fluoride. Thermogravimetric analyses (TGA) were performed on a Rigaku Denki thermal analytical apparatus "Thermoflex" using a temperature rate of rise of 10°C/ rain. The sample weight was varied between 500 and 600 rag. I.R. spectra of some products and of comparison compounds were recorded on a Hitachi infrared spectrophotometer EPI-2G from 4000 to 400 cm J as a Nujol Mull. Diffuse reflectance spectra of a product were obtained on a Hitachi U V and visible spectrophotometer EpS-3 from 340 to 700 m/z. RESULTS AND DISCUSSION Reactions of La20:~, Pr6011 , Nd203, Gd20.s, Dy~O:~and CeO, with Sb20:~ The result of reactions of equimolar quantities of rare earth oxide and Sb~O:~ is summarized in Table 1.
I. R. S. Roth, In The Progress in the Science and Technolo,~,,y o f the Rare Earths (Edited by L. Eyring), Vol. 1, p. 167. Pergamon Press, Oxford (1964). 2. H.W. Foote and E. K. Smith, J. Am. chem. Soc. 30, 1344 (1908). 3. I. Warshaw and R. Roy, J. phys. Chem. 65, 2048 (1961 ). 4. F. A. Myzenkov and D. N. Klushin, J. appl. Chem. USSR., 38, 1673 (1965). 681
682
Notes Table 1.Dataofthe systems Ln2Oz-Sb203 The system La203-Sb203 440-460oc 730-750°C 900-920oc 1090-1110oc 1300-1320oc 1500-1520oc
A-type La203 + Sb203 A-type La203 -1-5b204 A-type LazO3+ Sb204 + small amounts of La antimonate La antimonate La antimonate La antimonate
The system Pr6OH-3Sb203 360-380°C 530-550°C 900-920°C 1000-1020°C 1200-1220°C 1400-1420°C
C-type PrnOH + C-type PrnO~t + C-type Pr6OH + C-type Pr6Oll + Pr antimonate Pr antimonate
Sb203 SbzO4 Pr antimonate + 5b204 Pr antimonate + Sb204
The system Nd203-SbzO3 230-250°C 450-470°C 720-740°C 960-980°C 1200-1220°C 1430-1450°C
A-type Nd203 + Sb203 Unknown type Nd203 + 5b204 Diffuse X-ray patterns (Nd203 + 5b204) C-type NdzO3 solid solution with Sb204 + small amounts of Sb204 C-type Nd203 solid solution with Sb204 C-type NdzO3 solid solution with Sb204
The system Gd203-Sb203 350-370°C 680-700°C 910-930°C 1160-1190°C 1430-1450°C
C-type Gd203 + Sb204 Small amounts of C-type GdzO3 solid solution with Sb204 + 5b204 C-type Gd203 solid solution with 5b204+ small amounts of 5b204 C-type Gd203 solid solution with Sb204 C-type Gd20.~ solid solution with Sb~O4
The system DyeO3-Sb203 350-370°C 680-700°C 910-930°C 1100-1130°C 1370-1390°C 1430-1450°C
C-type Dy2Oa+ Sb203 C-type Dy203 + Sb2Oa C-type Dy203 solid solution with Sb204 + Sb204 C-type Dy203 solid solution with Sb204+ small amounts of Sb204 C-type Dy203 solid solution with Sb204 C-type Dy203 solid solution with Sb204
Rare earth antimonates were successfully accomplished in the systems La~203-Sb20z and Pr6Oll3SbzO3 but in the systems Nd~Oa-Gd203 and Dy203-Sb203 formations of solid solutions were observed only. Thus the antimonate compounds were formed with the "larger rare earth" oxides than praseodymium. By contrast, the solid solution were formed with the "smaller rare earth" oxides than neodymium.
Notes
683
A t t e m p t s to prepare cerium antimonate or cerium oxide-antimony oxide solid solution using ceric oxide or the products from the thermal decomposition of cerous salts for reaction with Sb~():~ in air were unsuccessful. Since ceric oxide CeO2 has a fluorite structure in which each metal ion is surrounded completely by eight o x y g e n atoms, it does not s e e m to form the formation of antimonate or solid solution with antimony oxide. A n t i m o n y trioxide was oxidized to Sb204 on heating the presence of rare earth oxide. A n t i m o n y trioxide itself melts at 625°C and above this temperature it has a considerably high vapour p r e s s u r e T h e vaporization of Sb2Oa, however, was s u p p r e s s e d in the co-existence of rare earth oxide and Sb~Oa was oxidized to Sb204 without the removal from the system. This s u p p r e s s i o n effect was inadequate with the "smaller" rare earth oxide than T b or with C e O > therefore some a m o u n t s of Sb2Oa were sublimated (Fig. 1).
Lo
0
E
:! 2o
o
\
"~.
". . . .
:\
'\
Gd
"
Nd
...... 222"22-: ..... ~.~
Tb a y Er
"" Ce
I
500 Temperature,
I0;0 (°C)
Fig. 1. T G A curves of the s y s t e m lm._,():~-Sb,,O:~. T h e reaction b e t w e e n rare earth oxides and Sb204 took place at t e m p e r a t u r e s of 900 ° to 1000°C. In the case of P r , O , , Pr 4+ contained in this oxide was reduced to Pr a+ when the antimonate formation occurred, this being confirmed by direct c o m p a r i s o n s with a Pr a~ authentic sample, PrCI:, hydrate, aml with the products formed at several t e m p e r a t u r e s using reflectance spectra (Fig. 2).
Chemical composition of hmthanum- tmd praseodymium-antimon~tte It was confirmed by X-ray fluorescent analysis that the atom ratios in these antimonate ([.a/Sb or Pr/Sb) were both 1:1 up to 1300°C. T h e tfiermogravimetric m e a s u r e m e n t indicated that Sb~Oa in the s y s t e m were oxidized to Sb~O, and that the composition of t h e s e a n t i m o n a t e s was Ln::Oa.Sb,.,O4 or Ln2Sb207 (Ln = La or Pr). I.R. spectra of L~zSb._,O7 and of Sb2Oa, SbzO~ and SbeO:, are s h o w n in Fig. 3. T h e portions of the spectra b e t w e e n 4000 and 1000 cm -~ show no characteristic features and have been omitted. T h e absorption m a x i m a in LaeSb,,O7 spectrum were in fair good agreement with the band centers of Sb204. Well-defined, sharp X-ray powder diffraction patterns were obtained on all of the synthesized products. It was possible to index all observed reflections of the L ~ S b 2 0 7 (Table 2) on the basis of tetragonal unit cell and of Nd, G d , and D y products on that of cubic unit cell. Diffraction patterns of PrzSb._,O7 were complex, so that indexing of them could not be done.
Solid solutions o f N d2Oa, G d._,Oa a n d Dy2Oa with antimony oxide T h e rare earth oxides described on the outside formed the " C - t y p e " solid solution with Sb~O~. While Nd~Oa used as a starting material was " A - t y p e " , it was transformed to "'C-type" solid solution during reaction. T h e a unit-cell p a r a m e t e r of C-type Nd2Oa is 11.07 A, but that of the solid solution Nd~Oa • 0.4 Sb~O4 which was formed at 1430°C was 10-81 _+0-01 A. In the s y s t e m Gd._,Oa-Sb._,O~ and DyeO::-
684
Notes
400
i
i
500
600
Wavelength, m~ Fig. 2. Reflectance spectra of the system Pr6Oll-3Sb203 at several temperatures. A, 900°; B, 1200°; C, 1400°; and D, PrCI 3 hydrate.
\".1
" "'.
"\ .~'>4" :'",." / W -- -- - C "...,.""'.,...: \,~..." " ......... O I
800
I
600
I
400
Wove n u m l ~ l ' , c m -I
Fig. 3. I.R. spectra of La~Sb2OT, Sb2Oz, Sb204 and Sb205. A, L~2Sb2OT; B, Sb205; C, Sb203; D, Sb204. Sb204, the solid solution Gd203 • 0"3Sb204 and Dy203 • 0"3SbzO4 were formed at the same temperature. The unit cell parameters of these solid solutions were also shortened as compared with those of pure oxides. (Gd203, a = 10.817 A,; Gd203 • 0.3 Sb204, a = 10.67_+0-03/~ Dy2Oa, a = 10.668 ,~,; Dy20 a - 0.3SbzO4, a = 10.51 _+0-07 ,~,) There are limits in the solubility of antimony oxide in these "C-type" rare earth oxides and antimony contents in the products described above appear to be the upper limits. It was confirmed that "A-type" rare earth oxide at room temperature formed generally antimonate but that "C-type" formed solid solution with antimony oxide.
Notes
685
Table 2. P o w d e r diffraction result for La,,Sb~OT, tetragonal, a = 7.15, A , c = 9 . 5 9 A .
hkl
dou~
d~t~d
1
hkl
d,,b~
d~,~,k.~l I
110
5"111
5-057
m
2.249 2-049
2-240 2.046
w w
002
4.848
4.797
m
1.994
1.992
m
200
3.604
3.576
s
1.855
1.853
s
112
3.507
3-481
s
1.838
1-833
m
210
3.232
3.202
s
1.692
1.691
m
202 022 113 220 300 203 023
2.867
2.867
s
2-700 2.529
2.703 2.529
m s
222 312 132 024 204 105 015 232 322 205 025 006 420 240
1.6(}0
1.599
m
2-386
2-384
w
Table 3. Powder diffraction result for PreSb207 doh~
/
d,,,~
1
3.562 3.520 3.389 3-278 3.209 3.142 3.110 3"028 2-885 2.822 2.755 2.714 2.691 2-660 2.550 2.338
s s m m w s s w w m m s m m m w
2-281 2.036 2.010 1.994 1.969 1.922 1.873 1-838 1.749 1.667 1.653 1.631 1.616 1.608 1-603 1-573
w w w w w s m s w w w w w w w w
Ceric oxide, one of " C - t y p e " oxide, formed neither a n t i m o n a t e nor solid solution be c a us e of its e x t r e m e l y inactive property.
Thermal stabilities of the products T h e relationship b e t w e e n a n t i m o n y c o n t e n t in the products and heating t e mpe ra t ure , that is, ther mal stability of the system, is s h o w n in Fig. 4. L a n t h a n u m - and P r-a nt i mona t e s were very stable and the d e c r e a s e in a n t i m o n y c o n t e n t was very little even at fairly high t e mpe ra t ure , while in the
686
Notes
~.o
~'"~:'~.
--N
~ ~'.
.
t.a
"._"x
Pr
..'-%,.,.
_5 o.5
Dy Gd
,I I000
5 0
Ce
I 1500
Temperature, °C
Fig. 4. Temperature dependence of antimony content in the products. system CeO~-Sb~Oa in which the reaction did not take place, vaporization of antimony oxide was drastic. In the systems where take out solid solutions were formed, the intermediate of the both behaviors described above was observed.
Department of Applied Chemist~ Faculty of Engineering Osaka University Osaka-fu, Japan
G. A D A C H I T. KAWAHITO H. MATSUMOTO J. SHIOKAWA
J. inorg, nucL Chem., 1970, Vol. 32, pp. 686 to 688.
Pergamon Press.
Printed in G r e a t Britain
A spectrophotometric determination of the stability constants of the iron(III)-8-hydroxyquinoline-7-sulfonic acid chelate (Received 6 May 1969) THE ~NTRODUCTION of 8-hydroxyquinoline as a reagent for the analysis of metal ions[l] opened a new field in analytical chemistry. By condensation and substitution reactions, certain groups can be introduced into the molecule so as to modify its complex forming properties. It has been shown that many metal ions do not form a precipitate with 8-hydroxyquinoline-5-sulfonic acid although colour changes are observed in many cases [2]. Banerji and Srivastava[3] have studied the reactions of 8-hydroxyquinoline-7-sulfonic acid with different metals and found that iron 01D develops a green colour in acidic media. Complex formation is instantaneous and the reaction is very sensitive. The composition of the complex has been determined[4] and we now report the determination of the first stability constant using a spectrophotometric method described previously by Anderson and Nickless [5]. EXPERIMENTAL A standard solution ofiron(lll) was prepared from a sample of ferric chloride (B.D.H.). 8-hydroxyl. 2. 3. 4. 5.
F. A. K. K. R.
L. Hahn, dngew. Chem. 39, 1198 (1926). Albert and D. Magrath, Biochem. J. 41,534 (1947). C. Srivastava and Samir K. Banerji, Chem. Age India 18, 351 (1967). Balachandran and Samir K. Banerji, J. prakt. Chem. 4, 37 (1968). G. Anderson and G. Nickless, Analytica chim. Acta 39, 469 (1967).
NOTES
The reactions of lanthanide oxides and antimony oxides (Received 9 June 1969)
INTRODUCTION Tins paper is concerned with the preparation of rare earth-antimony double oxides. A considerable amount of work has been done on rare earth-A~O3 systems[l], where A stands for trivalent metal ion, however no report has appeared on compounds of the rare earth oxides with antimony oxide. Behavior of antimony oxide at elevated temperatures is complicated. Antimony trioxide Sb20:, for instance, is oxidized to tetraoxide Sb..,O~ (which is double oxide between Sb._,O:~and Sb20~), which decomposes again to Sb203 at higher temperature [2]. There are three crystal systems in sesquioxides of the rare earths, including A-type (hexagonal), B-type (monoclinic) and C-type (cubic) as reported by Warshaw et a/.[3]. The present investigation was undertaken to see the relationships between reactions with antimony oxides and the crystal systems of rare earth oxides, especially lanthanum oxide, praseodymium oxide, neodymium oxide, gadolinium oxide and dysprosium oxide, in some detail. EXPERIMENTAL Rare earth oxides of 99.9 per cent purity (Lindsay Chemical Division, American Potash & Chemical Corporation) which had been pre-purified, were thoroughly mixed with antimony oxides (Sb.,O:~, Sb,,O4 or Sb~O.~) by grinding the fine powders together. Antimony trioxide and Sb=,O~ used were prepared by hydrolyses of SbCI.~ and SbCIs, respectively. Antimony tetraoxide was prepared by thermal decomposition of Sb20~. Each mixture was fired in an alumina crucible in open air for 2.5 hr at a fixed temperature, and then cooled in a furnace. X-ray diffraction patterns of the samples were obtained with a Rigaku Denki diffractometer "Geiger-flex" using Ni-filtered CuKt~ radiation at a scanning speed of 1° (2#)/min. X-ray fluorescent spectrographic analyses of rare earth elements and of antimony were made on a Rigaku Denki X-ray fluorescent spectrograph unit with scintillation counter (NaI:T1), tungsten target X-ray tube and lithium fluoride. Thermogravimetric analyses (TGA) were performed on a Rigaku Denki thermal analytical apparatus "Thermoflex" using a temperature rate of rise of 10°C/ rain. The sample weight was varied between 500 and 600 rag. I.R. spectra of some products and of comparison compounds were recorded on a Hitachi infrared spectrophotometer EPI-2G from 4000 to 400 cm J as a Nujol Mull. Diffuse reflectance spectra of a product were obtained on a Hitachi U V and visible spectrophotometer EpS-3 from 340 to 700 m/z. RESULTS AND DISCUSSION Reactions of La20:~, Pr6011 , Nd203, Gd20.s, Dy~O:~and CeO, with Sb20:~ The result of reactions of equimolar quantities of rare earth oxide and Sb~O:~ is summarized in Table 1.
I. R. S. Roth, In The Progress in the Science and Technolo,~,,y o f the Rare Earths (Edited by L. Eyring), Vol. 1, p. 167. Pergamon Press, Oxford (1964). 2. H.W. Foote and E. K. Smith, J. Am. chem. Soc. 30, 1344 (1908). 3. I. Warshaw and R. Roy, J. phys. Chem. 65, 2048 (1961 ). 4. F. A. Myzenkov and D. N. Klushin, J. appl. Chem. USSR., 38, 1673 (1965). 681
682
Notes Table 1.Dataofthe systems Ln2Oz-Sb203 The system La203-Sb203 440-460oc 730-750°C 900-920oc 1090-1110oc 1300-1320oc 1500-1520oc
A-type La203 + Sb203 A-type La203 -1-5b204 A-type LazO3+ Sb204 + small amounts of La antimonate La antimonate La antimonate La antimonate
The system Pr6OH-3Sb203 360-380°C 530-550°C 900-920°C 1000-1020°C 1200-1220°C 1400-1420°C
C-type PrnOH + C-type PrnO~t + C-type Pr6OH + C-type Pr6Oll + Pr antimonate Pr antimonate
Sb203 SbzO4 Pr antimonate + 5b204 Pr antimonate + Sb204
The system Nd203-SbzO3 230-250°C 450-470°C 720-740°C 960-980°C 1200-1220°C 1430-1450°C
A-type Nd203 + Sb203 Unknown type Nd203 + 5b204 Diffuse X-ray patterns (Nd203 + 5b204) C-type NdzO3 solid solution with Sb204 + small amounts of Sb204 C-type Nd203 solid solution with Sb204 C-type NdzO3 solid solution with Sb204
The system Gd203-Sb203 350-370°C 680-700°C 910-930°C 1160-1190°C 1430-1450°C
C-type Gd203 + Sb204 Small amounts of C-type GdzO3 solid solution with Sb204 + 5b204 C-type Gd203 solid solution with 5b204+ small amounts of 5b204 C-type Gd203 solid solution with Sb204 C-type Gd20.~ solid solution with Sb~O4
The system DyeO3-Sb203 350-370°C 680-700°C 910-930°C 1100-1130°C 1370-1390°C 1430-1450°C
C-type Dy2Oa+ Sb203 C-type Dy203 + Sb2Oa C-type Dy203 solid solution with Sb204 + Sb204 C-type Dy203 solid solution with Sb204+ small amounts of Sb204 C-type Dy203 solid solution with Sb204 C-type Dy203 solid solution with Sb204
Rare earth antimonates were successfully accomplished in the systems La~203-Sb20z and Pr6Oll3SbzO3 but in the systems Nd~Oa-Gd203 and Dy203-Sb203 formations of solid solutions were observed only. Thus the antimonate compounds were formed with the "larger rare earth" oxides than praseodymium. By contrast, the solid solution were formed with the "smaller rare earth" oxides than neodymium.
Notes
683
A t t e m p t s to prepare cerium antimonate or cerium oxide-antimony oxide solid solution using ceric oxide or the products from the thermal decomposition of cerous salts for reaction with Sb~():~ in air were unsuccessful. Since ceric oxide CeO2 has a fluorite structure in which each metal ion is surrounded completely by eight o x y g e n atoms, it does not s e e m to form the formation of antimonate or solid solution with antimony oxide. A n t i m o n y trioxide was oxidized to Sb204 on heating the presence of rare earth oxide. A n t i m o n y trioxide itself melts at 625°C and above this temperature it has a considerably high vapour p r e s s u r e T h e vaporization of Sb2Oa, however, was s u p p r e s s e d in the co-existence of rare earth oxide and Sb~Oa was oxidized to Sb204 without the removal from the system. This s u p p r e s s i o n effect was inadequate with the "smaller" rare earth oxide than T b or with C e O > therefore some a m o u n t s of Sb2Oa were sublimated (Fig. 1).
Lo
0
E
:! 2o
o
\
"~.
". . . .
:\
'\
Gd
"
Nd
...... 222"22-: ..... ~.~
Tb a y Er
"" Ce
I
500 Temperature,
I0;0 (°C)
Fig. 1. T G A curves of the s y s t e m lm._,():~-Sb,,O:~. T h e reaction b e t w e e n rare earth oxides and Sb204 took place at t e m p e r a t u r e s of 900 ° to 1000°C. In the case of P r , O , , Pr 4+ contained in this oxide was reduced to Pr a+ when the antimonate formation occurred, this being confirmed by direct c o m p a r i s o n s with a Pr a~ authentic sample, PrCI:, hydrate, aml with the products formed at several t e m p e r a t u r e s using reflectance spectra (Fig. 2).
Chemical composition of hmthanum- tmd praseodymium-antimon~tte It was confirmed by X-ray fluorescent analysis that the atom ratios in these antimonate ([.a/Sb or Pr/Sb) were both 1:1 up to 1300°C. T h e tfiermogravimetric m e a s u r e m e n t indicated that Sb~Oa in the s y s t e m were oxidized to Sb~O, and that the composition of t h e s e a n t i m o n a t e s was Ln::Oa.Sb,.,O4 or Ln2Sb207 (Ln = La or Pr). I.R. spectra of L~zSb._,O7 and of Sb2Oa, SbzO~ and SbeO:, are s h o w n in Fig. 3. T h e portions of the spectra b e t w e e n 4000 and 1000 cm -~ show no characteristic features and have been omitted. T h e absorption m a x i m a in LaeSb,,O7 spectrum were in fair good agreement with the band centers of Sb204. Well-defined, sharp X-ray powder diffraction patterns were obtained on all of the synthesized products. It was possible to index all observed reflections of the L ~ S b 2 0 7 (Table 2) on the basis of tetragonal unit cell and of Nd, G d , and D y products on that of cubic unit cell. Diffraction patterns of PrzSb._,O7 were complex, so that indexing of them could not be done.
Solid solutions o f N d2Oa, G d._,Oa a n d Dy2Oa with antimony oxide T h e rare earth oxides described on the outside formed the " C - t y p e " solid solution with Sb~O~. While Nd~Oa used as a starting material was " A - t y p e " , it was transformed to "'C-type" solid solution during reaction. T h e a unit-cell p a r a m e t e r of C-type Nd2Oa is 11.07 A, but that of the solid solution Nd~Oa • 0.4 Sb~O4 which was formed at 1430°C was 10-81 _+0-01 A. In the s y s t e m Gd._,Oa-Sb._,O~ and DyeO::-
684
Notes
400
i
i
500
600
Wavelength, m~ Fig. 2. Reflectance spectra of the system Pr6Oll-3Sb203 at several temperatures. A, 900°; B, 1200°; C, 1400°; and D, PrCI 3 hydrate.
\".1
" "'.
"\ .~'>4" :'",." / W -- -- - C "...,.""'.,...: \,~..." " ......... O I
800
I
600
I
400
Wove n u m l ~ l ' , c m -I
Fig. 3. I.R. spectra of La~Sb2OT, Sb2Oz, Sb204 and Sb205. A, L~2Sb2OT; B, Sb205; C, Sb203; D, Sb204. Sb204, the solid solution Gd203 • 0"3Sb204 and Dy203 • 0"3SbzO4 were formed at the same temperature. The unit cell parameters of these solid solutions were also shortened as compared with those of pure oxides. (Gd203, a = 10.817 A,; Gd203 • 0.3 Sb204, a = 10.67_+0-03/~ Dy2Oa, a = 10.668 ,~,; Dy20 a - 0.3SbzO4, a = 10.51 _+0-07 ,~,) There are limits in the solubility of antimony oxide in these "C-type" rare earth oxides and antimony contents in the products described above appear to be the upper limits. It was confirmed that "A-type" rare earth oxide at room temperature formed generally antimonate but that "C-type" formed solid solution with antimony oxide.
Notes
685
Table 2. P o w d e r diffraction result for La,,Sb~OT, tetragonal, a = 7.15, A , c = 9 . 5 9 A .
hkl
dou~
d~t~d
1
hkl
d,,b~
d~,~,k.~l I
110
5"111
5-057
m
2.249 2-049
2-240 2.046
w w
002
4.848
4.797
m
1.994
1.992
m
200
3.604
3.576
s
1.855
1.853
s
112
3.507
3-481
s
1.838
1-833
m
210
3.232
3.202
s
1.692
1.691
m
202 022 113 220 300 203 023
2.867
2.867
s
2-700 2.529
2.703 2.529
m s
222 312 132 024 204 105 015 232 322 205 025 006 420 240
1.6(}0
1.599
m
2-386
2-384
w
Table 3. Powder diffraction result for PreSb207 doh~
/
d,,,~
1
3.562 3.520 3.389 3-278 3.209 3.142 3.110 3"028 2-885 2.822 2.755 2.714 2.691 2-660 2.550 2.338
s s m m w s s w w m m s m m m w
2-281 2.036 2.010 1.994 1.969 1.922 1.873 1-838 1.749 1.667 1.653 1.631 1.616 1.608 1-603 1-573
w w w w w s m s w w w w w w w w
Ceric oxide, one of " C - t y p e " oxide, formed neither a n t i m o n a t e nor solid solution be c a us e of its e x t r e m e l y inactive property.
Thermal stabilities of the products T h e relationship b e t w e e n a n t i m o n y c o n t e n t in the products and heating t e mpe ra t ure , that is, ther mal stability of the system, is s h o w n in Fig. 4. L a n t h a n u m - and P r-a nt i mona t e s were very stable and the d e c r e a s e in a n t i m o n y c o n t e n t was very little even at fairly high t e mpe ra t ure , while in the
686
Notes
~.o
~'"~:'~.
--N
~ ~'.
.
t.a
"._"x
Pr
..'-%,.,.
_5 o.5
Dy Gd
,I I000
5 0
Ce
I 1500
Temperature, °C
Fig. 4. Temperature dependence of antimony content in the products. system CeO~-Sb~Oa in which the reaction did not take place, vaporization of antimony oxide was drastic. In the systems where take out solid solutions were formed, the intermediate of the both behaviors described above was observed.
Department of Applied Chemist~ Faculty of Engineering Osaka University Osaka-fu, Japan
G. A D A C H I T. KAWAHITO H. MATSUMOTO J. SHIOKAWA
J. inorg, nucL Chem., 1970, Vol. 32, pp. 686 to 688.
Pergamon Press.
Printed in G r e a t Britain
A spectrophotometric determination of the stability constants of the iron(III)-8-hydroxyquinoline-7-sulfonic acid chelate (Received 6 May 1969) THE ~NTRODUCTION of 8-hydroxyquinoline as a reagent for the analysis of metal ions[l] opened a new field in analytical chemistry. By condensation and substitution reactions, certain groups can be introduced into the molecule so as to modify its complex forming properties. It has been shown that many metal ions do not form a precipitate with 8-hydroxyquinoline-5-sulfonic acid although colour changes are observed in many cases [2]. Banerji and Srivastava[3] have studied the reactions of 8-hydroxyquinoline-7-sulfonic acid with different metals and found that iron 01D develops a green colour in acidic media. Complex formation is instantaneous and the reaction is very sensitive. The composition of the complex has been determined[4] and we now report the determination of the first stability constant using a spectrophotometric method described previously by Anderson and Nickless [5]. EXPERIMENTAL A standard solution ofiron(lll) was prepared from a sample of ferric chloride (B.D.H.). 8-hydroxyl. 2. 3. 4. 5.
F. A. K. K. R.
L. Hahn, dngew. Chem. 39, 1198 (1926). Albert and D. Magrath, Biochem. J. 41,534 (1947). C. Srivastava and Samir K. Banerji, Chem. Age India 18, 351 (1967). Balachandran and Samir K. Banerji, J. prakt. Chem. 4, 37 (1968). G. Anderson and G. Nickless, Analytica chim. Acta 39, 469 (1967).