- Email: [email protected]
Surface tension and density measurements of the molten YCl3-KCl binary system
Journal of the Lees-Common
Metals,
136 (1987)
111
111 - 119
SURFACE TENSION AND DENSITY MEASUREMENTS OF THE MOLTEN YCI,-KC1 BINARY SYSTEM G. LIU, N. M. STUBINA and J. M. TOGURI Department of Metallurgy and Materials Science, University 184 College Street, Toronto, Ontario, M5S IA4 fCanoda,I (Received February 23,1987;
of Toronto,
in revised form March 31,1987)
Summary The surface tension and the density of the YCl,-KC1 system were determined as a function of temperature (1073 - 1248 K) by the maximum bubble pressure technique. These results are represented by linear empirical equations as functions of temperature. At a constant temperature, the surface tensions of YCl,-KC1 melts show a negative deviation from Guggenheim’s equation for ideal solutions.
1. Introduction In recent years there has been an increasing demand for yttrium metal [l]. Yttrium can be used in garnets and ferrites for electronic components, as an alloying element for oxidation-resistant alloys [2 ] and for nuclear applications [ 31. One method of producing yttrium metal is by fused-salt electrolysis of a chloride melt containing yttrium. Also, yttrium has been electrorefined from a molten YCl,-KC1 bath f/i]. Nichkov et af. [5] measured the electrical conductivity of the YCls-KC1 binary system. Tomashov et al. [6] and Mochinaga and Irisawa [7] measured the density of this system. Unfortunately, surface tension data for the YCl,-KC1 melts are not available in the literature. In the present study, surface tensions and densities were simultaneously determined for the YCls-KC1 system using the maximum bubble pressure technique.
2. Experimental details The experimental apparatus and procedure used in the present study have been described in detail elsewhere [ 81 and thus only a brief description is presented here. The well established maximum bubble pressure technique @ Elsevier Se~uoial~rinted in The Netherlands
112
was selected for the simultaneous determination of the surface tension and the density of the YCls-KC1 system. The potassium chloride used in this study was obtained from Fisher Scientific (Fisher ACS grade). It was predried at 425 K under vacuum for three days. The yttrium chloride was purchased from Aldrich Chemical Co. Inc. It was slowly heated under vacuum from room temperature to 675 K over a period of 12 hours. Then, the salt was fused under a continuous flow of hydrogen chloride gas. After cooling, the salt was ground and some NH&I was added to it. The mixture was then kept at 575 K for 2 h. The salt was remelted under a constant flow of hydrogen chloride gas. Finally, chlorine gas and argon gas were in turn passed through the molten salt. The final product was analysed by differential thermal analysis (DTA) and by X-ray diffraction to ensure that the product was pure YCls. The high purity argon (99.999%) used to form the bubbles was passed through a copper getter furnace and through two drying columns (drier&e and phosphoric anhydride) in order to remove any residual water or oxygen. The desired salt mixture was contained in a quartz crucible under a purified argon atmosphere. The crucible had an inner diameter of 20 mm and a height of 60 mm. The quartz capillary was 50 mm in length, with an outer diameter of about 2.2 mm and an inner diameter of about 1.08 mm. The density of the molten salt mixture was calculated from the slope of the maximum pressure us. immersion depth curve. The surface tension could then be calculated using the Schrijdinger equation [8,9]. The effect of temperature on the surface tension and density was determined using both heating and cooling cycles. Since the salts wetted the capillary tip, the inner radius of the tip was used for the surface tension calculation. All measurements were corrected for the thermal expansion of the capillary orifice.
3. Results and discussion Surface tension and density data determined in the present study for pure KCl, pure YCl, and several YCls-KC1 mixtures are listed in Tables 1 and 2 respectively. For this apparatus, the total uncertainty in the surface tension measurements has been estimated to be approximately 3% [ 81. The dependence of surface tension on temperature, over a range from 1048 to 1248 K, for pure KC1 and pure YCls is shown graphically in Fig. 1. For KCl, data recommended by Janz et al. [lo] are included in the figure. Their recommended values are based on an averaged equation generated from several different investigations. The results from this study are in excellent agreement with the previously reported results. For YCls, surface tension results reported by,Igarashi et al. [ll] are included in Fig. 1. There is good agreement between the results from this study and their work for the higher temperature range (above 1175 K). For lower temperatures, however, there is a small difference between the curves. The corresponding density
100 87.5 75 58 40 25 12.5 0
0 12.5 25 42 60 75 87.5 100
84.3 84.0
IO48
(K)
81.6 81.1
95.8
97.4
1098
82.9 82.5
1073
Temperature
system
Surface tension values are given in mN m-*
YCI,
KC1
Composition (mol.%)
Surface tension values for the YClrKCl
TABLE 1
80.2 80.0 79.5 80.3 83.4 88.0 90.6 93.7
1123
78.8 78.6 78.0 78.8 82.1 86.2 89.2 91.8
1148
77.7 76.8 76.7 77‘4 80.4 84.8 87.3 90.0
1173
76.6 75.5 75.3 75.9 79.0 82.8 85.2 88.0
1198
75.1 74.4 73.6 74.7 77.3 81.1 83.6 86.1
1223
73.8 72.8 72.6 72.9 75.7 79.6 81.7 %4*3
1248
138.6 142.3 142.5 145.5 153.2 164.1 172.2 178.8
a
y=a+bT(K)
-5.19 -5.57 -5.61 -5.81 -6.21 -6.78 -7.25 -7.58
b(x 102)
0.13 OS6 0.15 0.14 0.11 0.14 0.18 0.12
Standard error of estimation
100 87.5 75 58 40 25 12.5 0
0 12.5 25 42 60 75 87.5 100
2.50 2.41
(K)
2.48 2.38
1.49
1.51
1098
2.49 2.39
I073
Density values are given in g ml-‘.
YClj
KC1
1048
Temperature
values for the YCIJ-KC1 system
Composition (mol.%)
Density
TABLE 2
2.47 2.36 2.24 2.10 1.95 1.80 1.65 1.48
1123
2.45 2.35 2.23 2.09 1.93 1.78 1.63 1.46
1148
2.44 2.33 2.22 2.07 1.92 1.77 1.61 1.45
1173
2.43 2.32 2.20 2.06 1.90 1.75 1.60 1.44
1198
2.42 2.30 2.18 2.04 1.88 1.73 1.58 1.42
1.223
2.40 2.29 2.17 2.03 1.87 1.71 1.57 1.41
1248
3.02 3.04 2.91 2.76 2.68 2.60 2.37 2.11
c
p=c+dT(K) 104)
-4.93 -6.00 -5.94 -5.83 -6.51 -7.09 -6.40 -5.62
d(X
3.3 3.2 4.1 3.0 3.3 3.2 3.8 3.3
x x x x x x x x
lo-3 1O-3 10-S 10-S 10-S 1O-3 10-S 10-3
Standard error of estimation
115 100.0
95.0
90.0
85.0
80.0
75.0
70.0
' 1025
I 1075
1
1
112s
Temperature
1
I
1175
122S
I 1175
(K)
Fig. 1. Effect of temperature on the surface tension of YCla-KC1 melts: A, 100 mol.% YC13; 0, 40%; 0, 25%; .X, 12.5%; 0, 0%; l, pure KC1 data from Janz et al. [lo]; A, pure YCls data from Igarashi et al. [ 111.
curves for the two pure salts are shown in Fig. 2. Results by Van Artsdalen and Yaffe [12] for pure KC1 and by Tomashov et al. [6] for pure YCls are included for comparison. The results from this study are in excellent agreement with these literature values. In Fig. 1, the surface tension measurements for various YCl,-KC1 mixtures are presented. For the sake of clarity, the lines corresponding to Xv”, = 0.58,0.75 and 0.875 are not included in the diagram. For each mixture, the surface tension of the melt decreases with increasing temperature in the range investigated. The corresponding density values for these melts are shown in Fig. 2. Included in this fii are results obtained by Tomashov et al. [6] and by Mochinaga and Irisawa [ 71. The results by Tomashov et al. [6] are for an Xvci, value of 0.395, wbereas the corresponding line in Fig. 2 is for an XycL, value of 0.40. Nevertheless, good agreement was attained. The results by Mochinaga and Irisawa [7] are for an Xv”, value of 0.158. As expected, their values fall between the lines for Xycl = 0.125 and Xvci = 0.25. For both surface tension and den&y, a decrease in \hese properties with increasing temperature was observed. Moreover, linear relationships of the form r=a+bT(K)
(mN m-l)
(1)
116 I
:,
I
1
I
I
I
:;
-
Y
2.10
-
1.90
-
1.70
-
1.50
-
V
x .?t o-l
k
n
1.30
0
.
4-iiwz
-
+, 1025
1075
1125
Temperature
1225
1175
1275
(K)
Fig. 2, Effect of temperature on the density of YC13-KC1 melts: A, 100 87.5%; *;75%; +, 68%; 0, 40%; 0, 25%; x, 12.5%; 0, 0%; 0, data from [6] (Xycl = 0.395); 0, data from Mochinaga and Irisawa [7] (Xycl,= KC1 data from Van Artsdalen and Yaffe [ 121; A, pure YCl3 data from
mol.% YCl,; q, Tomashov et al. 0.158); ., pure Tomashov et al.
[al. and p=c+dT(K)
(g ml-9
(2)
were obtained. The linear regression coefficients (a, b, c, and d) are summarized in Tables 1 and 2. The standard error of estimation is also included. Molar volumes (V) for the molten YCls-KC1 system can be calculated from the density data using the following relationship: v=
2 XiMi i
P
(3)
where Mi is the molecular weight of component i and Xi represents the mole fraction of component i in the salt. Molar volumes obtained in this study, as well as the values obtained based on a simple additive relationship, are shown in Fig. 3 for a temperature of 1123 K. Throughout the concentration range the experimental results show a positive departure from the additive relationship. This indicates that the structure of the YCl,-KCl mixture is “less cohesive” in comparison with the pure components. The maximum
117
YCI,-KCI
(T= 1123K)
65.0
Mol Fraction
YCI,
(XYC,
) 3
Fig. 3. Molar volume of the YCls-KC1 Mochinaga et al. [ 131.
system at 1123
K: 0, this work; a, data from
deviation between the experimental results and the additive line was approximately 2.7% and this was reached at Xv% = 0.58. This agrees with the results reported by Tomashov et al. [S 1. They found a maximum deviation of 2.8% for melts containing 60 - 65 mol.% yttrium chloride. Ikfochinaga et al. j133 measured the molar volumes of several molten salt systems. Some of their results were represented by empirical equations as functions of both temperature and composition. Their results at 1123 K are also shown in Fig. 3. The molar volumes calculated from their empirical ~uation and the molar volumes determined in this study are in good agreement, A surface tension isotherm for the YCl,-KC1 system at 1123 K is presented in Fig. 4. The surface tensions obtained in this study show a negative departure from Guggenheim’s‘ equation for ideal solutions [14]. In utilizing Guggenheim’s equation, it is assumed that the various components in the mixture have the same molar surface area. The shape of the curve in Fig. 4 is similar to the curve reported by Igarashi et al. [ll] for the YC13NaCl system.
118
YCI, -KCI 99.0
(T= 1123K)
I
I
I
I
I
I
I
90.0
85.0
SO.0
75.0
0.0
0.20
Fro::on
Y;;
1
I
(X,;;)
1.00
Mol 3 Fig. 4. Surface tension isotherm for the YCls-KC1 system at 1123 K: 0, this work.
The considerable negative deviation from Guggenheim’s equation [ 141, as well as the positive departure of the molar volumes from additivity, is
indicative of yttrium-chloro complexes in the melt, in lieu of simple Y3+ ions. Based on a study of the molar conductances of YCl,-KC1 melts, Tomashov et al. [6] have postulated that several yttrium-chloro complexes exist in the molten salt. The existence of these complexes was also reported by Nichkov et al. [ 51. These complex ions may have a larger size and a smaller charge number than the simple Y3+ ion. Therefore, it is to be expected that the interaction between these complex ions and other ions in the melt (e.g. Cl-) is smaller. Consequently, a decrease in the surface tension and an increase in the molar volume may result. Acknowledgment Financial support from the Natural Sciences and Engineering Research Council of Canada (NSERC) is gratefully acknowledged.
119
References
4
5 6 I 8 9 10 11 12 13 14
E. Morrice and M. M. Wong, Miner. Sci. Eng., 11(3) (1979) 125 - 136. H. E. Boyer and T. L. Gall (eds.), Metals Handbook@, Desk Edition, American Society for Metals, Metals Park, OH, 1985, p. 14.12. W. K. Anderson, Nuclear Applications of Yttrium and the Lanthanons, in F. H. Spedding and A. H. Daane (eds.), The Rare Earths, Wiley, New York, 1961, pp. 522 569. E. Morrice and R. G. Knickerbocker, Rare-Earth Electrolytic Metals, in F. H. Spedding and A. H. Daane (eds.), The Rare Earths, Wiley, New York, 1961, pp. 126 144. I. F. Nichkov, V. A. Tomashov and A. E. Mordovin, Russ. J. Znorg. Chem., 19(3), (1974) 448 - 450. V. A. Tomashov. I. F. Nichkov and A. E. Mordovin, Russ. J. Znorg. Chem., 20(11) (1975) 1696 - 1698. J. Mochinaga and K. Irisawa, Bull. Chem. Sot. Jpn., 47(2) (1974) 364 - 367. T. Fujisawa, T. Utigard and J. M. Toguri, Can. J. Chem., 63(5) (1985) 1132 - 1138. E. Schrijdinger, Ann. Phys. (Leipzig), 46 (1917) 488. G. J. Janz, R. P. T. Tomkins, C. B. Allen, J. R. Downey, Jr., G. L. Gardner, U. Krebs and S. K. Singer, J. Phys. Chem. Ref. Data, 4(4) (1975) 871 - 1178. K. Igarashi, J. Mochinaga and S. Ueda, Bull. Chem. Sot. Jpn., 51(5) (1978) 1551 1552. E. R. Van Artsdalen and I. S. Yaffe, J. Phys. Chem., 59(2) (1955) 118 - 127. J. Mochinaga, K. Igarashi, H. Kuroda and H. Iwasaki, Bull. Chem. Sot. Jpn., 49(9) (1976) 2625 - 2626. E. A. Guggenheim, Mixtures, Oxford University Press, London, 1952, p. 176.
Metals,
136 (1987)
111
111 - 119
SURFACE TENSION AND DENSITY MEASUREMENTS OF THE MOLTEN YCI,-KC1 BINARY SYSTEM G. LIU, N. M. STUBINA and J. M. TOGURI Department of Metallurgy and Materials Science, University 184 College Street, Toronto, Ontario, M5S IA4 fCanoda,I (Received February 23,1987;
of Toronto,
in revised form March 31,1987)
Summary The surface tension and the density of the YCl,-KC1 system were determined as a function of temperature (1073 - 1248 K) by the maximum bubble pressure technique. These results are represented by linear empirical equations as functions of temperature. At a constant temperature, the surface tensions of YCl,-KC1 melts show a negative deviation from Guggenheim’s equation for ideal solutions.
1. Introduction In recent years there has been an increasing demand for yttrium metal [l]. Yttrium can be used in garnets and ferrites for electronic components, as an alloying element for oxidation-resistant alloys [2 ] and for nuclear applications [ 31. One method of producing yttrium metal is by fused-salt electrolysis of a chloride melt containing yttrium. Also, yttrium has been electrorefined from a molten YCl,-KC1 bath f/i]. Nichkov et af. [5] measured the electrical conductivity of the YCls-KC1 binary system. Tomashov et al. [6] and Mochinaga and Irisawa [7] measured the density of this system. Unfortunately, surface tension data for the YCl,-KC1 melts are not available in the literature. In the present study, surface tensions and densities were simultaneously determined for the YCls-KC1 system using the maximum bubble pressure technique.
2. Experimental details The experimental apparatus and procedure used in the present study have been described in detail elsewhere [ 81 and thus only a brief description is presented here. The well established maximum bubble pressure technique @ Elsevier Se~uoial~rinted in The Netherlands
112
was selected for the simultaneous determination of the surface tension and the density of the YCls-KC1 system. The potassium chloride used in this study was obtained from Fisher Scientific (Fisher ACS grade). It was predried at 425 K under vacuum for three days. The yttrium chloride was purchased from Aldrich Chemical Co. Inc. It was slowly heated under vacuum from room temperature to 675 K over a period of 12 hours. Then, the salt was fused under a continuous flow of hydrogen chloride gas. After cooling, the salt was ground and some NH&I was added to it. The mixture was then kept at 575 K for 2 h. The salt was remelted under a constant flow of hydrogen chloride gas. Finally, chlorine gas and argon gas were in turn passed through the molten salt. The final product was analysed by differential thermal analysis (DTA) and by X-ray diffraction to ensure that the product was pure YCls. The high purity argon (99.999%) used to form the bubbles was passed through a copper getter furnace and through two drying columns (drier&e and phosphoric anhydride) in order to remove any residual water or oxygen. The desired salt mixture was contained in a quartz crucible under a purified argon atmosphere. The crucible had an inner diameter of 20 mm and a height of 60 mm. The quartz capillary was 50 mm in length, with an outer diameter of about 2.2 mm and an inner diameter of about 1.08 mm. The density of the molten salt mixture was calculated from the slope of the maximum pressure us. immersion depth curve. The surface tension could then be calculated using the Schrijdinger equation [8,9]. The effect of temperature on the surface tension and density was determined using both heating and cooling cycles. Since the salts wetted the capillary tip, the inner radius of the tip was used for the surface tension calculation. All measurements were corrected for the thermal expansion of the capillary orifice.
3. Results and discussion Surface tension and density data determined in the present study for pure KCl, pure YCl, and several YCls-KC1 mixtures are listed in Tables 1 and 2 respectively. For this apparatus, the total uncertainty in the surface tension measurements has been estimated to be approximately 3% [ 81. The dependence of surface tension on temperature, over a range from 1048 to 1248 K, for pure KC1 and pure YCls is shown graphically in Fig. 1. For KCl, data recommended by Janz et al. [lo] are included in the figure. Their recommended values are based on an averaged equation generated from several different investigations. The results from this study are in excellent agreement with the previously reported results. For YCls, surface tension results reported by,Igarashi et al. [ll] are included in Fig. 1. There is good agreement between the results from this study and their work for the higher temperature range (above 1175 K). For lower temperatures, however, there is a small difference between the curves. The corresponding density
100 87.5 75 58 40 25 12.5 0
0 12.5 25 42 60 75 87.5 100
84.3 84.0
IO48
(K)
81.6 81.1
95.8
97.4
1098
82.9 82.5
1073
Temperature
system
Surface tension values are given in mN m-*
YCI,
KC1
Composition (mol.%)
Surface tension values for the YClrKCl
TABLE 1
80.2 80.0 79.5 80.3 83.4 88.0 90.6 93.7
1123
78.8 78.6 78.0 78.8 82.1 86.2 89.2 91.8
1148
77.7 76.8 76.7 77‘4 80.4 84.8 87.3 90.0
1173
76.6 75.5 75.3 75.9 79.0 82.8 85.2 88.0
1198
75.1 74.4 73.6 74.7 77.3 81.1 83.6 86.1
1223
73.8 72.8 72.6 72.9 75.7 79.6 81.7 %4*3
1248
138.6 142.3 142.5 145.5 153.2 164.1 172.2 178.8
a
y=a+bT(K)
-5.19 -5.57 -5.61 -5.81 -6.21 -6.78 -7.25 -7.58
b(x 102)
0.13 OS6 0.15 0.14 0.11 0.14 0.18 0.12
Standard error of estimation
100 87.5 75 58 40 25 12.5 0
0 12.5 25 42 60 75 87.5 100
2.50 2.41
(K)
2.48 2.38
1.49
1.51
1098
2.49 2.39
I073
Density values are given in g ml-‘.
YClj
KC1
1048
Temperature
values for the YCIJ-KC1 system
Composition (mol.%)
Density
TABLE 2
2.47 2.36 2.24 2.10 1.95 1.80 1.65 1.48
1123
2.45 2.35 2.23 2.09 1.93 1.78 1.63 1.46
1148
2.44 2.33 2.22 2.07 1.92 1.77 1.61 1.45
1173
2.43 2.32 2.20 2.06 1.90 1.75 1.60 1.44
1198
2.42 2.30 2.18 2.04 1.88 1.73 1.58 1.42
1.223
2.40 2.29 2.17 2.03 1.87 1.71 1.57 1.41
1248
3.02 3.04 2.91 2.76 2.68 2.60 2.37 2.11
c
p=c+dT(K) 104)
-4.93 -6.00 -5.94 -5.83 -6.51 -7.09 -6.40 -5.62
d(X
3.3 3.2 4.1 3.0 3.3 3.2 3.8 3.3
x x x x x x x x
lo-3 1O-3 10-S 10-S 10-S 1O-3 10-S 10-3
Standard error of estimation
115 100.0
95.0
90.0
85.0
80.0
75.0
70.0
' 1025
I 1075
1
1
112s
Temperature
1
I
1175
122S
I 1175
(K)
Fig. 1. Effect of temperature on the surface tension of YCla-KC1 melts: A, 100 mol.% YC13; 0, 40%; 0, 25%; .X, 12.5%; 0, 0%; l, pure KC1 data from Janz et al. [lo]; A, pure YCls data from Igarashi et al. [ 111.
curves for the two pure salts are shown in Fig. 2. Results by Van Artsdalen and Yaffe [12] for pure KC1 and by Tomashov et al. [6] for pure YCls are included for comparison. The results from this study are in excellent agreement with these literature values. In Fig. 1, the surface tension measurements for various YCl,-KC1 mixtures are presented. For the sake of clarity, the lines corresponding to Xv”, = 0.58,0.75 and 0.875 are not included in the diagram. For each mixture, the surface tension of the melt decreases with increasing temperature in the range investigated. The corresponding density values for these melts are shown in Fig. 2. Included in this fii are results obtained by Tomashov et al. [6] and by Mochinaga and Irisawa [ 71. The results by Tomashov et al. [6] are for an Xvci, value of 0.395, wbereas the corresponding line in Fig. 2 is for an XycL, value of 0.40. Nevertheless, good agreement was attained. The results by Mochinaga and Irisawa [7] are for an Xv”, value of 0.158. As expected, their values fall between the lines for Xycl = 0.125 and Xvci = 0.25. For both surface tension and den&y, a decrease in \hese properties with increasing temperature was observed. Moreover, linear relationships of the form r=a+bT(K)
(mN m-l)
(1)
116 I
:,
I
1
I
I
I
:;
-
Y
2.10
-
1.90
-
1.70
-
1.50
-
V
x .?t o-l
k
n
1.30
0
.
4-iiwz
-
+, 1025
1075
1125
Temperature
1225
1175
1275
(K)
Fig. 2, Effect of temperature on the density of YC13-KC1 melts: A, 100 87.5%; *;75%; +, 68%; 0, 40%; 0, 25%; x, 12.5%; 0, 0%; 0, data from [6] (Xycl = 0.395); 0, data from Mochinaga and Irisawa [7] (Xycl,= KC1 data from Van Artsdalen and Yaffe [ 121; A, pure YCl3 data from
mol.% YCl,; q, Tomashov et al. 0.158); ., pure Tomashov et al.
[al. and p=c+dT(K)
(g ml-9
(2)
were obtained. The linear regression coefficients (a, b, c, and d) are summarized in Tables 1 and 2. The standard error of estimation is also included. Molar volumes (V) for the molten YCls-KC1 system can be calculated from the density data using the following relationship: v=
2 XiMi i
P
(3)
where Mi is the molecular weight of component i and Xi represents the mole fraction of component i in the salt. Molar volumes obtained in this study, as well as the values obtained based on a simple additive relationship, are shown in Fig. 3 for a temperature of 1123 K. Throughout the concentration range the experimental results show a positive departure from the additive relationship. This indicates that the structure of the YCl,-KCl mixture is “less cohesive” in comparison with the pure components. The maximum
117
YCI,-KCI
(T= 1123K)
65.0
Mol Fraction
YCI,
(XYC,
) 3
Fig. 3. Molar volume of the YCls-KC1 Mochinaga et al. [ 131.
system at 1123
K: 0, this work; a, data from
deviation between the experimental results and the additive line was approximately 2.7% and this was reached at Xv% = 0.58. This agrees with the results reported by Tomashov et al. [S 1. They found a maximum deviation of 2.8% for melts containing 60 - 65 mol.% yttrium chloride. Ikfochinaga et al. j133 measured the molar volumes of several molten salt systems. Some of their results were represented by empirical equations as functions of both temperature and composition. Their results at 1123 K are also shown in Fig. 3. The molar volumes calculated from their empirical ~uation and the molar volumes determined in this study are in good agreement, A surface tension isotherm for the YCl,-KC1 system at 1123 K is presented in Fig. 4. The surface tensions obtained in this study show a negative departure from Guggenheim’s‘ equation for ideal solutions [14]. In utilizing Guggenheim’s equation, it is assumed that the various components in the mixture have the same molar surface area. The shape of the curve in Fig. 4 is similar to the curve reported by Igarashi et al. [ll] for the YC13NaCl system.
118
YCI, -KCI 99.0
(T= 1123K)
I
I
I
I
I
I
I
90.0
85.0
SO.0
75.0
0.0
0.20
Fro::on
Y;;
1
I
(X,;;)
1.00
Mol 3 Fig. 4. Surface tension isotherm for the YCls-KC1 system at 1123 K: 0, this work.
The considerable negative deviation from Guggenheim’s equation [ 141, as well as the positive departure of the molar volumes from additivity, is
indicative of yttrium-chloro complexes in the melt, in lieu of simple Y3+ ions. Based on a study of the molar conductances of YCl,-KC1 melts, Tomashov et al. [6] have postulated that several yttrium-chloro complexes exist in the molten salt. The existence of these complexes was also reported by Nichkov et al. [ 51. These complex ions may have a larger size and a smaller charge number than the simple Y3+ ion. Therefore, it is to be expected that the interaction between these complex ions and other ions in the melt (e.g. Cl-) is smaller. Consequently, a decrease in the surface tension and an increase in the molar volume may result. Acknowledgment Financial support from the Natural Sciences and Engineering Research Council of Canada (NSERC) is gratefully acknowledged.
119
References
4
5 6 I 8 9 10 11 12 13 14
E. Morrice and M. M. Wong, Miner. Sci. Eng., 11(3) (1979) 125 - 136. H. E. Boyer and T. L. Gall (eds.), Metals Handbook@, Desk Edition, American Society for Metals, Metals Park, OH, 1985, p. 14.12. W. K. Anderson, Nuclear Applications of Yttrium and the Lanthanons, in F. H. Spedding and A. H. Daane (eds.), The Rare Earths, Wiley, New York, 1961, pp. 522 569. E. Morrice and R. G. Knickerbocker, Rare-Earth Electrolytic Metals, in F. H. Spedding and A. H. Daane (eds.), The Rare Earths, Wiley, New York, 1961, pp. 126 144. I. F. Nichkov, V. A. Tomashov and A. E. Mordovin, Russ. J. Znorg. Chem., 19(3), (1974) 448 - 450. V. A. Tomashov. I. F. Nichkov and A. E. Mordovin, Russ. J. Znorg. Chem., 20(11) (1975) 1696 - 1698. J. Mochinaga and K. Irisawa, Bull. Chem. Sot. Jpn., 47(2) (1974) 364 - 367. T. Fujisawa, T. Utigard and J. M. Toguri, Can. J. Chem., 63(5) (1985) 1132 - 1138. E. Schrijdinger, Ann. Phys. (Leipzig), 46 (1917) 488. G. J. Janz, R. P. T. Tomkins, C. B. Allen, J. R. Downey, Jr., G. L. Gardner, U. Krebs and S. K. Singer, J. Phys. Chem. Ref. Data, 4(4) (1975) 871 - 1178. K. Igarashi, J. Mochinaga and S. Ueda, Bull. Chem. Sot. Jpn., 51(5) (1978) 1551 1552. E. R. Van Artsdalen and I. S. Yaffe, J. Phys. Chem., 59(2) (1955) 118 - 127. J. Mochinaga, K. Igarashi, H. Kuroda and H. Iwasaki, Bull. Chem. Sot. Jpn., 49(9) (1976) 2625 - 2626. E. A. Guggenheim, Mixtures, Oxford University Press, London, 1952, p. 176.