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The pseudo-binary phase diagram Agl-Aul
Journal of the Less-Common Metals, 59 (1978) P65 - P72 El Elsevier Sequoia S.A., Lausanne -- Printed in the Netherlands
THE PSEUDO-BINARY
P65
PHASE DIAGRAM AgI-Au1
E. M. W. JANSSEN Materials Science Centre of the University, Laboratorium Nijen borgh 16, 9 747 AG Groningen (The Netherlands) (Received
November
voor Anorganische
Chemie,
16, 1977)
Summary The pseudo-binary system AgI-Au1 has been studied by differential thermal analysis (DTA); high temperature X-ray diffraction was also applied. Au1 dissolves in a-AgI over a wide temperature range forming a solid solution with disorder of the metal atoms. A eutectic point was found at 86 “C and Age,,, Auo,sOI. The newly discovered compound AgAuI, has three structural modifications. At 55 “C r-AgAuI, transforms into p-AgAuI, and at 127 “C! /3-AgAuIa transforms into ol-AgAuIa.
1. Introduction In recent years there has been considerable interest in materials with fast ion transport, the so-called super-ionic conductors, especially in view of their applications in solid state batteries [ 11. Examples of such materials include several halides and chalcogenides of Ag, e.g. AgI and Ag,S. The high temperature (Yforms of these compounds which are stable above 149 “C and 179 “C, respectively, have crystal structures with a strongly disordered cation lattice; the number of lattice sites is much larger than the number of cations present. The ionic conductivities are high because all the metal ions are free to move, the activation energy being small. The ionic conductivity is much smaller in the ordered low temperature p forms. It is of interest to prepare materials in which fast ion transport occurs at rather low temperatures (0 - 100 “C). One expects that the solution of gold in a silver compound will lead to a decrease in the order-disorder transition temperature from the 0 to the (Yform. Such a decrease has been observed in the system Ag, _ .yAu,S [2]. In this way, the range of temperature in which fast ion transport occurs can be extended considerably. A similar effect would be expected in the system Ag, _ ,Au,I. In this paper we report an investigation of the pseudo-binary phase diagram AgI-AuI. It is indeed found that the disordered (Yphase is stable down to a eutectic temperature of 86 “C for the composition Ag,,,,AuO,soI.
P66 2.
Experimental
The pseudo-binary phase diagram AgI-Au1 was investigated using differential thermal analysis (DTA). For the determination of the phase diagram, samples weighing about 50 mg were prepared in the DTA ampoules. Doubly sublimed iodine was mixed with reactive gold and silver powder in quartz ampoules (with an additional piece of quartz to minimize the dead volume). The metaI:iodine ratio of the samples was not exactly 1:l because of the rapid evaporation of iodine. The samples were heated at 120 “C for one week. The DTA measurements were performed as described previously
131. X-ray power diffraction diagrams and high temperature X-ray diagrams of Ag0,50Au0,501 were taken with a Guinier-Len& camera (Nonius) at a heating rate of about 1 “C h- ’ and a cooling rate of about 5 “C h _’ ; the slit width was 3 mm and the rate of film transport was 1 or 2 mm h’-’ [3] .
3. Results Some characteristic DTA curves are shown in Figs. 1 - 5. DTA curves of samples with the composition Agl_xA~, I (0 < x < 0.3) show four successive transformations (Fig. 1). The first two signals were sharp and occurred at 55 “C and 86 “C, respectively, for all compositions between AgI and Age.,, of the other two signals varied with composition. Au,, I. The temperature These tail-shaped signals can be ascribed to a two-phase region. The signal below 150 “C is due to the two-phase region of p-AgI and the (Yphase, a solid solution of Au1 dissolved in cu-AgI. The high temperature signal is caused by the two-phase region of the Q phase and a liquid phase L. 1 ”
a!;: __,’
----__, +
i‘i[=--.._
II 3jMcm hI<_&_
: 3)iVlcm
__--d
--_/
,:
I 3. // I _---$ml
a
Fig. 1. Heating and cooling DTA curves of 50 AU0.181.
mg samples of &a.ssAUo.esI and &o.sz-
---Mmg
b
fig. 2. Heating
and cooling
Ag,,Auoz
-5Omg Ag,,, Auox6 Sensfttvlty 3p;icm Heattng rote L hn
I I
DTA curves of 50 mg samples
of Ag0.70Au0.2gI
and Ago.61 -
A’Jo.361.
Ago~70Auo~2gIshowed only three peaks (Fig. 2); the first two (at 55 “C and 86 “C) are sharp; the third one, occurring at 470 - 485 “C, is tail-shaped. This indicates the existence of a eutectic point at 3c = 0.3 and 86 “C. For Ago,,Au0.3sI, four transformations were observed (Fig. 2). A sample I did not show the transition at 86 “C with the composition Ago,,A~O,W (Fig. 3). This behaviour suggests the existence of a new solid compound AgAuI,. The first transition at 55 “C can be ascribed to a change in the structure of AgAul,; this was confirmed by high temperature X-ray diffraction of AgAuI,. The signal at 127 “C!corresponds to the transition of fl-AgAu12 to the disordered (Yphase. Thus the new compound AgAuI, undergoes the following phase transitions: -Mmg PgIiisAu,, 1 --~
-------___,
I ‘\ t_._ A -----_____
Fig. 3. Heating AUo.%I.
and cooling
4,/ _____-_A\is-- -*’
50mg A~,,,Au~~~
1
I’ -TIC1
DTA curves of 50 mg samples
of Ag0.4gAuO.501
and Ag,-,aa-
P68
7 -A&M,
A
55 *c
-P
P-AgAuI,
127 Oc
01-AgAuIs
The existence of AgAufs as a solid compound and the st~ct~~~al transition at 55 “C were confirmed by DTA runs of samples of Ag, _ XAu,1 (X > 0.5). For Ag,,,Au a.J (Fig, 3) and Ag a.soAu,s,I (Fig. 4), no transition was found at 86 “C although the transition at 55 “C was observed. DTA curves of samples with the composition Ag, _ x Au, I (0.65 < x < 0.8’7) (Figs. 4 and 5) showed transitions at different temperatures from those of A& _ XAu, I (0 < x < 0.5) with the exception of the first transition at 55 “C!.The transition at 122 “C is presumably due to another eutectoid with
2b ---=‘=, -5
__s-----_
Fig. 4. Heating and cooling DTA curves af 50 mg
samples of Ag0.ssA~s5I
and Age.ns-
AUO.I$
R A *_----_
Ocm
,--‘-td
_,?/I
/“+
l2
r7
;
--_
I:
--*_,
-\,
44 i--d
--___-
,x-’ //
\I b
L ltquld
t 1, c ---------_____ ----f I
50
la0
150
200
250
300
Fig. 5. Heating and cooling DTA curves of 50 AUO.871*
TI’CI 3 350
.-.J
I
mg samples af Ago.19Auo.781
and Ag0.12-
P69
a composition between Ag,,, A~c.~e1 and Ages, Auc.s51. For Agas, Aua.s& a third transformation took place at about 136 “C (Fig. 4). After annealing the sample at about 300 “C for one month, this transition was more pronounced. For Ago,,,Auo,,sI a transition was observed at 184 “C during the first run; this transition had disappeared in the second run, presumable because the sample was initially inhomogeneous (Fig. 4). For samples with a larger content of AuI, the transition at 184 “C was always present and did not disappear after annealing (Fig. 5). This transition at 184 “C is probably related to the transition at the same temperature in Au1 [4]. A transformation to a liquid phase coexisting with metallic gold was observed at 310 “C for Ago.,, AuO.87 1. The reactivity of Au1 impeded a detailed study of the phase diagram AgI-Au1 near the composition AuI.
TABLE
1
Powder
pattern
hkl
d talc
001 110
6.424 6.371
111 200 201 211 002 221 310 202 212 400
4.524 4.505 3.689 3.414 3.212 2.854 2.849 2.615 2.512 2.253
TABLE Observed hkl
110 200 211 220 310 222 321
of y-AgAuI2
i
t
I
d obs
I obs
hkl
6.371
st
410 312
4.500
W
3.681 3.408 3.211
vs m
2.848 2.612 2.507 2.251
S S vs W
m
411 420 322 203 421 402 332 431 501 422 004
I
d talc . 2.185 2.132
d ohs
Iohs
2.183 2.129
S
2.069 2.015 1.972 1.934 1.922 1.844 1.772
2.068 2.014 1.972 1.934 1.923 1.845 1.770
1.735
1.735
1.707 1.606
1.707 1.606
m
W
W W W
m W+
m W+ W
W
2 and calculated
powder
pattern
a-AgI
of (Y-AgI and cu-AgAuI2 cl-AgAu12
d
I obs
Icdc
d obs
d talc
I obs
I talc
3.58 2.53 2.066 1.788 1.600 1.457 1.353
vs st st m/w
100 64 84 20 15 4 19
3.615 2.546 2.077 1.802 1.610 _ 1.361
3.600 2.545 2.078 1.800 1.610 _
vs VW st m VW VW
100 4 52 43 13 0 14
W
_ m
1.361
P70 556 11’
?lO 18L
I
_‘.I’
_
__
. -. j3-AgIt $-AgAuI,
2:
,
,
0
-
1
-
_L
_.
86
--
~-iqAu12+AuI
I
I
I
'4
A%_xAu,*
1. _I
t
---
55
AU1
AgAuI,
asI
-_,
1
J3-Ag1+P-AsA’
136 127 122
+AuI
f_LAgAu12
j
l&7
,.L--
3k
'12
1
x
Fig. 6. The pseudo-binary phase diagram AgI-AuI. The dots represent DTA observations. The disordered cyphase has a large homogeneity region.
From X-ray powder diffraction data it was found that the low temperature modification y-AgAuI, is tetragonal with a = 9.010 a, c = 6.424 8, and c/a = 1.4026 (Table 1). The tetragonal cell is related to the unit cell of T-AgI (f.c.c. with a = 6.495 a) [ 51. From high temperature X-ray data obtained
P71
with a Guinier-Len& camera it was found that /3-AgAuIa is probably also tetragonal, with a c axis twice as long as that of r-AgAuI,. The high temperature modification a-AgAuIa (a = 5.091 a at about 130 “C) has a disordered structure similar to that of a-AgI. a-AgI has a bodycentred cubic structure with a = 5.048 .& at about 150 “C [ 61. The disordered arrangement of the metal atoms has been described as a statistical distribution over the positions 6(b), 12(d) and 24(h) of space group Im3m; the iodine atoms are at the positions 2(a), i.e. O,O,O and %,%,% of the unit cell [ 71. The intensity sequence of the reflections of a-AgAuI,, especially the intensity ratio of 200 and 220, differ considerably from those of cu-AgI. This can be explained by placing the gold atoms statistically on positions 8(c): (O,O,O; l/2,%,%) + 1/4,%,X; ‘/4,3/4,Y4; 3/4,1/4,%;%,3/4,%. These positions are the centres of the eight octants in the cell. Table 2 compares the powder pattern of a-AgAuIa with that of cr-AgI. It appears that the proposed positions explain the changes in the observed intensities quite well.
4. Discussion The resulting pseudo-binary phase diagram, shown in Fig. 6, is similar to the phase diagram of the pseudo-binary AgaS-AgAy$ system [ 5,8] . The solution of gold in AgI indeed decreases the order-disorder transition temperature from the p to the 01form; a eutectic point was found at 86 “C and Ago.,, Auo.soI. AgAuIa can easily be prepared by heating the elements at 120 “C for one week; it has three structural modifications. The high temperature form a-AgAuIs has a structure related to that of disordered a-AgI. It may be noted that similar changes in intensity were found for the system Ag, _ XAu,S [ 21. In both series of solid solutions the Au atoms are in linear coordination with I and S atoms, respectively.
Acknowledgments I thank Dr. G. A. Wiegers, Professor Jellinek for their interest in this work.
Dr. C. Haas and Professor
Dr. F.
References 1 W. van Go01 (ed.), Fast Ion Transport in Solids, North-Holland Publ. Co., Amsterdam, 1973. 2 J. C. W. Folmer, P. Hofman and G. A. Wiegers, J. Less-Common Met., 48 (1976) 251. 3 E. M. W. Janssen, F. Pohlmann and G. A. Wiegers, J. Less-Common Met., 45 (1976) 261.
P72 4 E. M. W. Janssen, Thesis, Groningen, 1977. 5 H. E. Swanson, M. I. Cook, T. Isaacs and E. H. Evans, Nat]. Bur. Stand. 539,9 (1960) 48. 6 W. Strock, Z. Phys. Chem., 25 (1934) 441. 7 S. Hoshino, J. Phys.Soc. Jpn., 12 (1957) 315. 8 R. B. Graf, Am. Mineral., 53 (1968) 496.
(U.S.),
Circ.,
THE PSEUDO-BINARY
P65
PHASE DIAGRAM AgI-Au1
E. M. W. JANSSEN Materials Science Centre of the University, Laboratorium Nijen borgh 16, 9 747 AG Groningen (The Netherlands) (Received
November
voor Anorganische
Chemie,
16, 1977)
Summary The pseudo-binary system AgI-Au1 has been studied by differential thermal analysis (DTA); high temperature X-ray diffraction was also applied. Au1 dissolves in a-AgI over a wide temperature range forming a solid solution with disorder of the metal atoms. A eutectic point was found at 86 “C and Age,,, Auo,sOI. The newly discovered compound AgAuI, has three structural modifications. At 55 “C r-AgAuI, transforms into p-AgAuI, and at 127 “C! /3-AgAuIa transforms into ol-AgAuIa.
1. Introduction In recent years there has been considerable interest in materials with fast ion transport, the so-called super-ionic conductors, especially in view of their applications in solid state batteries [ 11. Examples of such materials include several halides and chalcogenides of Ag, e.g. AgI and Ag,S. The high temperature (Yforms of these compounds which are stable above 149 “C and 179 “C, respectively, have crystal structures with a strongly disordered cation lattice; the number of lattice sites is much larger than the number of cations present. The ionic conductivities are high because all the metal ions are free to move, the activation energy being small. The ionic conductivity is much smaller in the ordered low temperature p forms. It is of interest to prepare materials in which fast ion transport occurs at rather low temperatures (0 - 100 “C). One expects that the solution of gold in a silver compound will lead to a decrease in the order-disorder transition temperature from the 0 to the (Yform. Such a decrease has been observed in the system Ag, _ .yAu,S [2]. In this way, the range of temperature in which fast ion transport occurs can be extended considerably. A similar effect would be expected in the system Ag, _ ,Au,I. In this paper we report an investigation of the pseudo-binary phase diagram AgI-AuI. It is indeed found that the disordered (Yphase is stable down to a eutectic temperature of 86 “C for the composition Ag,,,,AuO,soI.
P66 2.
Experimental
The pseudo-binary phase diagram AgI-Au1 was investigated using differential thermal analysis (DTA). For the determination of the phase diagram, samples weighing about 50 mg were prepared in the DTA ampoules. Doubly sublimed iodine was mixed with reactive gold and silver powder in quartz ampoules (with an additional piece of quartz to minimize the dead volume). The metaI:iodine ratio of the samples was not exactly 1:l because of the rapid evaporation of iodine. The samples were heated at 120 “C for one week. The DTA measurements were performed as described previously
131. X-ray power diffraction diagrams and high temperature X-ray diagrams of Ag0,50Au0,501 were taken with a Guinier-Len& camera (Nonius) at a heating rate of about 1 “C h- ’ and a cooling rate of about 5 “C h _’ ; the slit width was 3 mm and the rate of film transport was 1 or 2 mm h’-’ [3] .
3. Results Some characteristic DTA curves are shown in Figs. 1 - 5. DTA curves of samples with the composition Agl_xA~, I (0 < x < 0.3) show four successive transformations (Fig. 1). The first two signals were sharp and occurred at 55 “C and 86 “C, respectively, for all compositions between AgI and Age.,, of the other two signals varied with composition. Au,, I. The temperature These tail-shaped signals can be ascribed to a two-phase region. The signal below 150 “C is due to the two-phase region of p-AgI and the (Yphase, a solid solution of Au1 dissolved in cu-AgI. The high temperature signal is caused by the two-phase region of the Q phase and a liquid phase L. 1 ”
a!;: __,’
----__, +
i‘i[=--.._
II 3jMcm hI<_&_
: 3)iVlcm
__--d
--_/
,:
I 3. // I _---$ml
a
Fig. 1. Heating and cooling DTA curves of 50 AU0.181.
mg samples of &a.ssAUo.esI and &o.sz-
---Mmg
b
fig. 2. Heating
and cooling
Ag,,Auoz
-5Omg Ag,,, Auox6 Sensfttvlty 3p;icm Heattng rote L hn
I I
DTA curves of 50 mg samples
of Ag0.70Au0.2gI
and Ago.61 -
A’Jo.361.
Ago~70Auo~2gIshowed only three peaks (Fig. 2); the first two (at 55 “C and 86 “C) are sharp; the third one, occurring at 470 - 485 “C, is tail-shaped. This indicates the existence of a eutectic point at 3c = 0.3 and 86 “C. For Ago,,Au0.3sI, four transformations were observed (Fig. 2). A sample I did not show the transition at 86 “C with the composition Ago,,A~O,W (Fig. 3). This behaviour suggests the existence of a new solid compound AgAuI,. The first transition at 55 “C can be ascribed to a change in the structure of AgAul,; this was confirmed by high temperature X-ray diffraction of AgAuI,. The signal at 127 “C!corresponds to the transition of fl-AgAu12 to the disordered (Yphase. Thus the new compound AgAuI, undergoes the following phase transitions: -Mmg PgIiisAu,, 1 --~
-------___,
I ‘\ t_._ A -----_____
Fig. 3. Heating AUo.%I.
and cooling
4,/ _____-_A\is-- -*’
50mg A~,,,Au~~~
1
I’ -TIC1
DTA curves of 50 mg samples
of Ag0.4gAuO.501
and Ag,-,aa-
P68
7 -A&M,
A
55 *c
-P
P-AgAuI,
127 Oc
01-AgAuIs
The existence of AgAufs as a solid compound and the st~ct~~~al transition at 55 “C were confirmed by DTA runs of samples of Ag, _ XAu,1 (X > 0.5). For Ag,,,Au a.J (Fig, 3) and Ag a.soAu,s,I (Fig. 4), no transition was found at 86 “C although the transition at 55 “C was observed. DTA curves of samples with the composition Ag, _ x Au, I (0.65 < x < 0.8’7) (Figs. 4 and 5) showed transitions at different temperatures from those of A& _ XAu, I (0 < x < 0.5) with the exception of the first transition at 55 “C!.The transition at 122 “C is presumably due to another eutectoid with
2b ---=‘=, -5
__s-----_
Fig. 4. Heating and cooling DTA curves af 50 mg
samples of Ag0.ssA~s5I
and Age.ns-
AUO.I$
R A *_----_
Ocm
,--‘-td
_,?/I
/“+
l2
r7
;
--_
I:
--*_,
-\,
44 i--d
--___-
,x-’ //
\I b
L ltquld
t 1, c ---------_____ ----f I
50
la0
150
200
250
300
Fig. 5. Heating and cooling DTA curves of 50 AUO.871*
TI’CI 3 350
.-.J
I
mg samples af Ago.19Auo.781
and Ag0.12-
P69
a composition between Ag,,, A~c.~e1 and Ages, Auc.s51. For Agas, Aua.s& a third transformation took place at about 136 “C (Fig. 4). After annealing the sample at about 300 “C for one month, this transition was more pronounced. For Ago,,,Auo,,sI a transition was observed at 184 “C during the first run; this transition had disappeared in the second run, presumable because the sample was initially inhomogeneous (Fig. 4). For samples with a larger content of AuI, the transition at 184 “C was always present and did not disappear after annealing (Fig. 5). This transition at 184 “C is probably related to the transition at the same temperature in Au1 [4]. A transformation to a liquid phase coexisting with metallic gold was observed at 310 “C for Ago.,, AuO.87 1. The reactivity of Au1 impeded a detailed study of the phase diagram AgI-Au1 near the composition AuI.
TABLE
1
Powder
pattern
hkl
d talc
001 110
6.424 6.371
111 200 201 211 002 221 310 202 212 400
4.524 4.505 3.689 3.414 3.212 2.854 2.849 2.615 2.512 2.253
TABLE Observed hkl
110 200 211 220 310 222 321
of y-AgAuI2
i
t
I
d obs
I obs
hkl
6.371
st
410 312
4.500
W
3.681 3.408 3.211
vs m
2.848 2.612 2.507 2.251
S S vs W
m
411 420 322 203 421 402 332 431 501 422 004
I
d talc . 2.185 2.132
d ohs
Iohs
2.183 2.129
S
2.069 2.015 1.972 1.934 1.922 1.844 1.772
2.068 2.014 1.972 1.934 1.923 1.845 1.770
1.735
1.735
1.707 1.606
1.707 1.606
m
W
W W W
m W+
m W+ W
W
2 and calculated
powder
pattern
a-AgI
of (Y-AgI and cu-AgAuI2 cl-AgAu12
d
I obs
Icdc
d obs
d talc
I obs
I talc
3.58 2.53 2.066 1.788 1.600 1.457 1.353
vs st st m/w
100 64 84 20 15 4 19
3.615 2.546 2.077 1.802 1.610 _ 1.361
3.600 2.545 2.078 1.800 1.610 _
vs VW st m VW VW
100 4 52 43 13 0 14
W
_ m
1.361
P70 556 11’
?lO 18L
I
_‘.I’
_
__
. -. j3-AgIt $-AgAuI,
2:
,
,
0
-
1
-
_L
_.
86
--
~-iqAu12+AuI
I
I
I
'4
A%_xAu,*
1. _I
t
---
55
AU1
AgAuI,
asI
-_,
1
J3-Ag1+P-AsA’
136 127 122
+AuI
f_LAgAu12
j
l&7
,.L--
3k
'12
1
x
Fig. 6. The pseudo-binary phase diagram AgI-AuI. The dots represent DTA observations. The disordered cyphase has a large homogeneity region.
From X-ray powder diffraction data it was found that the low temperature modification y-AgAuI, is tetragonal with a = 9.010 a, c = 6.424 8, and c/a = 1.4026 (Table 1). The tetragonal cell is related to the unit cell of T-AgI (f.c.c. with a = 6.495 a) [ 51. From high temperature X-ray data obtained
P71
with a Guinier-Len& camera it was found that /3-AgAuIa is probably also tetragonal, with a c axis twice as long as that of r-AgAuI,. The high temperature modification a-AgAuIa (a = 5.091 a at about 130 “C) has a disordered structure similar to that of a-AgI. a-AgI has a bodycentred cubic structure with a = 5.048 .& at about 150 “C [ 61. The disordered arrangement of the metal atoms has been described as a statistical distribution over the positions 6(b), 12(d) and 24(h) of space group Im3m; the iodine atoms are at the positions 2(a), i.e. O,O,O and %,%,% of the unit cell [ 71. The intensity sequence of the reflections of a-AgAuI,, especially the intensity ratio of 200 and 220, differ considerably from those of cu-AgI. This can be explained by placing the gold atoms statistically on positions 8(c): (O,O,O; l/2,%,%) + 1/4,%,X; ‘/4,3/4,Y4; 3/4,1/4,%;%,3/4,%. These positions are the centres of the eight octants in the cell. Table 2 compares the powder pattern of a-AgAuIa with that of cr-AgI. It appears that the proposed positions explain the changes in the observed intensities quite well.
4. Discussion The resulting pseudo-binary phase diagram, shown in Fig. 6, is similar to the phase diagram of the pseudo-binary AgaS-AgAy$ system [ 5,8] . The solution of gold in AgI indeed decreases the order-disorder transition temperature from the p to the 01form; a eutectic point was found at 86 “C and Ago.,, Auo.soI. AgAuIa can easily be prepared by heating the elements at 120 “C for one week; it has three structural modifications. The high temperature form a-AgAuIs has a structure related to that of disordered a-AgI. It may be noted that similar changes in intensity were found for the system Ag, _ XAu,S [ 21. In both series of solid solutions the Au atoms are in linear coordination with I and S atoms, respectively.
Acknowledgments I thank Dr. G. A. Wiegers, Professor Jellinek for their interest in this work.
Dr. C. Haas and Professor
Dr. F.
References 1 W. van Go01 (ed.), Fast Ion Transport in Solids, North-Holland Publ. Co., Amsterdam, 1973. 2 J. C. W. Folmer, P. Hofman and G. A. Wiegers, J. Less-Common Met., 48 (1976) 251. 3 E. M. W. Janssen, F. Pohlmann and G. A. Wiegers, J. Less-Common Met., 45 (1976) 261.
P72 4 E. M. W. Janssen, Thesis, Groningen, 1977. 5 H. E. Swanson, M. I. Cook, T. Isaacs and E. H. Evans, Nat]. Bur. Stand. 539,9 (1960) 48. 6 W. Strock, Z. Phys. Chem., 25 (1934) 441. 7 S. Hoshino, J. Phys.Soc. Jpn., 12 (1957) 315. 8 R. B. Graf, Am. Mineral., 53 (1968) 496.
(U.S.),
Circ.,