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Phase equilibria in TiO2+alkali metal borate systems
Notes
3041
because the complex has a cis square planar structure. The estimated haft-band widths (~lt~) of approximately 30 cm -1 are typical of N-bonded thiocyanate 0'in = 30-40 cm-1); the S-bonded group gives much sharper C - N stretching peaks (v~n ----12-18 cm -1) [5]. Triphenylarsine sulphide appears to have overall class "b" ligand character [6, 10, 11] and the formation of N-bonded thiocyanate complexes is consistent with this observation. EXPERIMENTAL Preparation of complexes Solutions of K~M(SCN)4(M=Pd,Pt) ( - 0.2 mmole) in water (15 ml) were extracted with chloroform solutions (15 ml) of the ligands (0-5-1.0 mmole). The chloroform layers became deep orange-red (Pd) or yellow (Pt). The monomeric PhsAsS complexes were isolated from the concentrated chloroform solutions by t.l.c. (SiOt, 1 : 1 benzene-chloroform) (A), but this method did not yield pure products with the other ligands. The extracts with PhaPS and PhsPSe were evaporated to dryness, boiled with carbon tetrachloride to remove unreacted ligand, and recrystallised from chloroform to separate the soluble dimeric (B) and insoluble trimeric complexes (C). The compound 3Pt(CNS)2,2PhsPS was converted to 2Pt(CNSh,PlhPS by boiling in chloroform for I hr (D). This process would lead ultimately to the formation of the parent thiocyanates M(SCN)2 but the X-ray powder diffraction patterns of our palladium complexes contained no lines characteristic of Pd(SCNh.
Extraction data Extraction of palladium from the aqueous layer was followed spoctrophotometrieally at 400 nm, until no change in palladium concentration was observed over a period of at least 24 hr. Extraction of ligand into the aqueous phase did not occur to a detectable extent. Our thanks are due to SRC for a maintenance grant (to MGK) and to Mrs K. Bull for practical assistance. Department of Chemistry University of A berdeen Old Aberdeen
M. G. K I N G G. P. M c Q U I L L A N R. M I L N E
10. P. E. Nicpon and D. W. Meek, Chem. Comm. 398 (1966). 1 i. A. M. Brodie, S. H. Hunter, G. A. Rodley and C. J. Wilkins, J. chem. Soc. (A), 2039 (1968).
J. inorg, nucl. Chem., 1973, Vol. 35, pp. 3041-3043.
Pergamon Press.
Printed in Great Britain
Phase equilibria in TiO2~ alkali metal borate systems (First received 25 August 1972; in revised form 8 December 1972) IN THE course of a study on extraction of TiOe from TiO2-rich slags, we have investigated solutions of TiO~ in fused alkali metal borates. The solubility of TiOs in a variety of molten salt solvents has been reported, but apparently only four pure alkali metal borate solvents have been studied[l, 2]. It has been established that TiO2 is not always recrystallised from fused alkali borate solutions. In particular, potassium hexatitanate (K~O.6TiO2) is formed in solutions of TiO2 in both potassium diborate (KzO'2B2Oa) [2, 3] and metaborate (KzO'BsOa)[3]. Dissolution of TiOs in Na20-BsO3 similarly yields Na20.6TiO2, but TiO2 is the principal titanium species crystallized from NazO'2B203 solutions of TiO2 [1,3]. 1. I. N. Anlkin, I. I. Naumova and G. V. Rumyantseva, Soy. Phys. Crystallogr. 10, 172 (I 965). 2. I. I. Naumova and I. N. Anikin, Russ. J. inorg. Chem. 11,934 (1966). 3. A.J. Easteal and D. J. Udy, Submitted for publication.
3042
Notes
G
C
I000
900
,.L\/
k"
600
A+B+L O°o
fl
o
°
o
~'~d/o
B+C+L
o
,4+B+C 700
I
I
o
,o
2'0
1o
4'o
I
5o
6'o
K z O ' 6 T I O 2 + K 2 0 " 2 B2 03 ,
7'o
,;o
mole %
Fig. 1. P h a s e diagram for the pseudo-binary s y s t e m K20"B203 + (equimolar K~O'6TiO2/ K20"2B203). ,4 = K 2 0 ' B 2 0 3 ; B = K20"6TiO2; C = K20"2B2Os; L = liquid.
// IO00
900
P k"
800 '% •
/
/
/
_ __'_,J__
700 I
0
lio
i
O
.
30
.
.
40
.
50
NO20"6TiO2+No20"2B203,
60
71
O
i
0
mole %
Fig. 2. Phase diagram f o r the pseudo-binary system N a 2 0 . B = O 3 + ( e q u i m o l a r Na~O. 6 T i O 2 / N a 2 0 . 2 B , O3).
Notes
3043
EXPERIMENTAL Na~O'B203 and K20"B203 were prepared by reacting Anala R grade Na~CO3 and K2CO3 respectively, in equimolar ratio with Riedel-De Haen A.G. standard grade BzO3. TiO2 was supplied by British Drug Houses. TiO2 was added in weighed portions to the alkali metaborate contained in a Pt/5% Au crucible, and the mixture equilibrated at ca. 1000°C. Cooling curves were then recorded using a calibrated Pt vs Pt + 13% Rh thermocouple. Components in solidified melts were identified by X-ray powder diffraction as previously described [3]. RESULTS AND DISCUSSION From solutions of 30 mol% TiO2 in Na20"B203 and 20 mol% TiO2 in K20"2B203, at ca. 1000°C, Na20'6TiO2 and K20"6TiO2 respectively were the only titanium compounds detected in the solidified melts at room temperature [3]. The reaction occurring in the melts to produce alkali hexatitanate may thus be formally represented by the equilibrium 2 (M20-B203) + 6TiO2 ~ M20"6TiO2 + M20"2B203.
( 1)
Since no TiO2 was detected in the room temperature solids the equilibrium constant for reaction 1 is assumed to be large. Thus, dissolution of TiOz in M20-B2Oa generates the ternary system M20-B203 + M20-6TiO2 + MzO'2B203. Variation of the initial TiO2 content is equivalent to traversal of a slice of the ternary system, since the components MzO-6TiOz and M20-2B203 have a constant 1 : 1 tool ratio. The results of thermal analysis of the TiOz + K20"BzO3 system are shown in Fig. 1 in the form of a phase diagram for the pseudo-binary system K20'B203 + (equimolar K20"6TiO2/K20"2BzO3). The binary pair K20'B203/K20"2B203 shows only simple eutectic interaction[4]. We assume that the other binary pairs, K~O'B203/K20"6TiOz and KzO'2B2Oa/K20"6TiO2, likewise exhibit simple eutectic interaction. Further, the eutectic compositions for these two binaries are likely to tie in the boraterich region, since the freezing point of K20"6TiO2 (1370°C[5]) is considerably higher than those of KK20-2B20~ (815°C[6]) and K20"BzO3 (915°C [6]). These considerations allow the liquidus curves ab, bc and de of Fig. 1 to be attributed to crystallization of K20"B2Oa, K~O'6TiO2 and K20"2B203 respectively. Detection of phase transitions in the TiO2+ Na~O'B~O3 system was more difficult than in the potassium case, because melts had a greater tendency to supercool without crystallization. By analogy with Fig. 1 the thermal analysis results for the sodium system are represented by the pseudo-binary phase diagram shown in Fig. 2. A c k n o w l e d g e m e n t - W e are indebted to New Zealand Steel Ltd. for a research fellowship and to the New Zealand Universities Research Grants Committee for equipment grants. Department o f Chemistry University o f A uckland Auckland New Zealand
A. J. E A S T E A L D. J. U D Y
4. A. P. Rollett, C. r. hebd. S$anc. Acad. Sci. Paris 200, 1764 (1935); ibid. 202, 1864 (1936). 5. K. L. Berry, V. D. Aftandilian, W. W. Gilbert, E. P. H. Meibohm and H. S. Young, J. inorg, nucl. Chem. 14, 231 (1960). 6. E. M. Levin, C. R. Robbins and H. F. McMurdie, Phase Diagrams for Ceramists. The American Ceramic Society (1964).
3041
because the complex has a cis square planar structure. The estimated haft-band widths (~lt~) of approximately 30 cm -1 are typical of N-bonded thiocyanate 0'in = 30-40 cm-1); the S-bonded group gives much sharper C - N stretching peaks (v~n ----12-18 cm -1) [5]. Triphenylarsine sulphide appears to have overall class "b" ligand character [6, 10, 11] and the formation of N-bonded thiocyanate complexes is consistent with this observation. EXPERIMENTAL Preparation of complexes Solutions of K~M(SCN)4(M=Pd,Pt) ( - 0.2 mmole) in water (15 ml) were extracted with chloroform solutions (15 ml) of the ligands (0-5-1.0 mmole). The chloroform layers became deep orange-red (Pd) or yellow (Pt). The monomeric PhsAsS complexes were isolated from the concentrated chloroform solutions by t.l.c. (SiOt, 1 : 1 benzene-chloroform) (A), but this method did not yield pure products with the other ligands. The extracts with PhaPS and PhsPSe were evaporated to dryness, boiled with carbon tetrachloride to remove unreacted ligand, and recrystallised from chloroform to separate the soluble dimeric (B) and insoluble trimeric complexes (C). The compound 3Pt(CNS)2,2PhsPS was converted to 2Pt(CNSh,PlhPS by boiling in chloroform for I hr (D). This process would lead ultimately to the formation of the parent thiocyanates M(SCN)2 but the X-ray powder diffraction patterns of our palladium complexes contained no lines characteristic of Pd(SCNh.
Extraction data Extraction of palladium from the aqueous layer was followed spoctrophotometrieally at 400 nm, until no change in palladium concentration was observed over a period of at least 24 hr. Extraction of ligand into the aqueous phase did not occur to a detectable extent. Our thanks are due to SRC for a maintenance grant (to MGK) and to Mrs K. Bull for practical assistance. Department of Chemistry University of A berdeen Old Aberdeen
M. G. K I N G G. P. M c Q U I L L A N R. M I L N E
10. P. E. Nicpon and D. W. Meek, Chem. Comm. 398 (1966). 1 i. A. M. Brodie, S. H. Hunter, G. A. Rodley and C. J. Wilkins, J. chem. Soc. (A), 2039 (1968).
J. inorg, nucl. Chem., 1973, Vol. 35, pp. 3041-3043.
Pergamon Press.
Printed in Great Britain
Phase equilibria in TiO2~ alkali metal borate systems (First received 25 August 1972; in revised form 8 December 1972) IN THE course of a study on extraction of TiOe from TiO2-rich slags, we have investigated solutions of TiO~ in fused alkali metal borates. The solubility of TiOs in a variety of molten salt solvents has been reported, but apparently only four pure alkali metal borate solvents have been studied[l, 2]. It has been established that TiO2 is not always recrystallised from fused alkali borate solutions. In particular, potassium hexatitanate (K~O.6TiO2) is formed in solutions of TiO2 in both potassium diborate (KzO'2B2Oa) [2, 3] and metaborate (KzO'BsOa)[3]. Dissolution of TiOs in Na20-BsO3 similarly yields Na20.6TiO2, but TiO2 is the principal titanium species crystallized from NazO'2B203 solutions of TiO2 [1,3]. 1. I. N. Anlkin, I. I. Naumova and G. V. Rumyantseva, Soy. Phys. Crystallogr. 10, 172 (I 965). 2. I. I. Naumova and I. N. Anikin, Russ. J. inorg. Chem. 11,934 (1966). 3. A.J. Easteal and D. J. Udy, Submitted for publication.
3042
Notes
G
C
I000
900
,.L\/
k"
600
A+B+L O°o
fl
o
°
o
~'~d/o
B+C+L
o
,4+B+C 700
I
I
o
,o
2'0
1o
4'o
I
5o
6'o
K z O ' 6 T I O 2 + K 2 0 " 2 B2 03 ,
7'o
,;o
mole %
Fig. 1. P h a s e diagram for the pseudo-binary s y s t e m K20"B203 + (equimolar K~O'6TiO2/ K20"2B203). ,4 = K 2 0 ' B 2 0 3 ; B = K20"6TiO2; C = K20"2B2Os; L = liquid.
// IO00
900
P k"
800 '% •
/
/
/
_ __'_,J__
700 I
0
lio
i
O
.
30
.
.
40
.
50
NO20"6TiO2+No20"2B203,
60
71
O
i
0
mole %
Fig. 2. Phase diagram f o r the pseudo-binary system N a 2 0 . B = O 3 + ( e q u i m o l a r Na~O. 6 T i O 2 / N a 2 0 . 2 B , O3).
Notes
3043
EXPERIMENTAL Na~O'B203 and K20"B203 were prepared by reacting Anala R grade Na~CO3 and K2CO3 respectively, in equimolar ratio with Riedel-De Haen A.G. standard grade BzO3. TiO2 was supplied by British Drug Houses. TiO2 was added in weighed portions to the alkali metaborate contained in a Pt/5% Au crucible, and the mixture equilibrated at ca. 1000°C. Cooling curves were then recorded using a calibrated Pt vs Pt + 13% Rh thermocouple. Components in solidified melts were identified by X-ray powder diffraction as previously described [3]. RESULTS AND DISCUSSION From solutions of 30 mol% TiO2 in Na20"B203 and 20 mol% TiO2 in K20"2B203, at ca. 1000°C, Na20'6TiO2 and K20"6TiO2 respectively were the only titanium compounds detected in the solidified melts at room temperature [3]. The reaction occurring in the melts to produce alkali hexatitanate may thus be formally represented by the equilibrium 2 (M20-B203) + 6TiO2 ~ M20"6TiO2 + M20"2B203.
( 1)
Since no TiO2 was detected in the room temperature solids the equilibrium constant for reaction 1 is assumed to be large. Thus, dissolution of TiOz in M20-B2Oa generates the ternary system M20-B203 + M20-6TiO2 + MzO'2B203. Variation of the initial TiO2 content is equivalent to traversal of a slice of the ternary system, since the components MzO-6TiOz and M20-2B203 have a constant 1 : 1 tool ratio. The results of thermal analysis of the TiOz + K20"BzO3 system are shown in Fig. 1 in the form of a phase diagram for the pseudo-binary system K20'B203 + (equimolar K20"6TiO2/K20"2BzO3). The binary pair K20'B203/K20"2B203 shows only simple eutectic interaction[4]. We assume that the other binary pairs, K~O'B203/K20"6TiOz and KzO'2B2Oa/K20"6TiO2, likewise exhibit simple eutectic interaction. Further, the eutectic compositions for these two binaries are likely to tie in the boraterich region, since the freezing point of K20"6TiO2 (1370°C[5]) is considerably higher than those of KK20-2B20~ (815°C[6]) and K20"BzO3 (915°C [6]). These considerations allow the liquidus curves ab, bc and de of Fig. 1 to be attributed to crystallization of K20"B2Oa, K~O'6TiO2 and K20"2B203 respectively. Detection of phase transitions in the TiO2+ Na~O'B~O3 system was more difficult than in the potassium case, because melts had a greater tendency to supercool without crystallization. By analogy with Fig. 1 the thermal analysis results for the sodium system are represented by the pseudo-binary phase diagram shown in Fig. 2. A c k n o w l e d g e m e n t - W e are indebted to New Zealand Steel Ltd. for a research fellowship and to the New Zealand Universities Research Grants Committee for equipment grants. Department o f Chemistry University o f A uckland Auckland New Zealand
A. J. E A S T E A L D. J. U D Y
4. A. P. Rollett, C. r. hebd. S$anc. Acad. Sci. Paris 200, 1764 (1935); ibid. 202, 1864 (1936). 5. K. L. Berry, V. D. Aftandilian, W. W. Gilbert, E. P. H. Meibohm and H. S. Young, J. inorg, nucl. Chem. 14, 231 (1960). 6. E. M. Levin, C. R. Robbins and H. F. McMurdie, Phase Diagrams for Ceramists. The American Ceramic Society (1964).