Isotherms of viscosity against molar compositions have been investigated over extended temperature ranges for the systems KCl-LiCl and KCl-NaCl and the activation energy for viscous flow are calculated with Eyring's theory. The activation energy showed negative deviation from additivity in KCl-LiCl system, but in KCl-NaCl system the activation energy showed positive deviation from additivity in the range of 0〜40 mol % NaCl and showed negative deviation in the range of 40〜100 mol % NaCl. These deviations are caused by the interaction between different types of molecules or ion pairs in the liquid mixture

MATSUMURA, Yoshitaka

MIZUNO, Masao

NISHIHARA, Kiyokado

English

Kyoto University Research Information Repository

RIGHT:URL:CITATION:AUTHOR(S):ISSUE DATE:TITLE:The Viscosity of the Fused SaltsMixtures : KCl-LiCl and KCl-NaClSystemsMATSUMURA, Yoshitaka; MIZUNO, Masao;NISHIHARA, KiyokadoMATSUMURA, Yoshitaka ...[et al]. The Viscosity of the Fused Salts Mixtures : KCl-LiCl andKCl-NaCl Systems. Memoirs of the Faculty of Engineering, Kyoto University 1966, 28(4):404-4121966-11-30http://hdl.handle.net/2433/280671404 The Viscosity of the Fused Salts Mixtures (KCl-LiCl and KCl-NaCl Systems) By Yoshitaka MATSUMURA*, Masao MIZUNO* and Kiyokado NISHIHARA** (Received June 28, 1966) Isotherms of viscosity against molar compositions have been investigated over extended temperature ranges for the systems KCI-LiCI and KCI-NaCI and the acti-vation energy for viscous flow are calculated with Eyring's theory. The activation energy showed negative deviation from additivity in KCI-LiCI system, but in KCI-NaCI system the activation energy showed positive deviation from additivity in the range of 0~40 mo! % NaCl and showed negative deviation in the range of40~100 mo!% NaCl. These deviations are caused by the interaction between different types of molecules or ion pairs in the liquid mixture. 1. Introduction The viscosity of the fused salts mixture has been investigated by J. Kendal11), E. Heymann, H. Bloom2) and others3)-6), both from the practical standpoint of wanting to be able to predict the viscosity of fused salts mixture from the properties of the pure components and from the theoretical viewpoint of wishing to gain a clearer insight into the behavior of liquid mixtures. It has been recognized that viscosity-composition curves are not simple func-tions of composition, they may have a maximum, a minimum, neither, or both. One of the early equations, and certainly one of the most popular concerning the viscosity of a liquid to temperature is r; = A exp (Ev;s/RT) . A constant Evis : activation energy for viscous flow R gas constant T absolute temperature r; viscosity of fused salt * Department of Metal Science and Technology. ** Department of Metallurgy. ( 1 ) The Viscosiry of the Fused Saltsffi Mixtures 405 H. Erying7) added theoretical significance in the equation it the following form: ( 2) A distance between two equilibrium positions for viscous flow A1 distance between two layers of molecules A2 mean distance between two adjacent molecules in the moving layer in the direction at a right angle to the direction of the motion A3 distance between neighboring molecules in the same direction of motion h Planck constant JG activation energy Although A is not necessarily equal to A1, the two quantities are of the same order of magnitude, and if, as a first approximation, they are taken to be identical, and the product A1A2A3 is approximately the volume inhabited by a single molecule in the liquid state, equation (2) may be written as; or r; = (Nh/V) exp (JG/RT) = B exp (Evis/RT) r;/p = (Nh/M) exp (JG/RT) = B' exp (Evis/RT) N Avogadro number V molar volume M molar weight /J density of fused salt B,B': constant ( 3) (4) From equation (4) we calculated the values of activation energy for viscous flow of fused salts. We investigated the viscosity of fused KCl-LiCl and KCl-NaCl mixtures which are the basic components of fused salts electrolyte and fluxes for welding or brazing of aluminum and its alloys. The isotherms of viscosity against molar compositions were determined over extended temperature ranges for these systems and the value of activation energy for viscous flow was calculated. 2. Apparatus and Experimental Procedure The viscosity of fused KCl-LiCl and KCl-NaCl systems were measured by the damped oscillating disc methods) at temperatures 700° ,..__,900°C. The ex-406 Yoshitaka MATSUMURA, Masao MIZUNO and Kiyodado NISHIHARA perimental apparatus is shown in Fig. 1. The platinum disc (30 mm diameter and 2 mm thickness) is suspended from stainless steel wire (0.3 mm diameter and 1,060 mm long). This platinum disc is immersed into the fused salt, which is con-tained in a platinum dish (95 mm diameter and 45 mm depth). In the several preliminary experiments with aqueous solutions of H2SO 4 in various concentrations, Stainless steel wire / Platinum disc c=;,;;:::;;::::,_, / Furnace / _ -Fused flux Fig. I. Apparatus for determination of viscosity. and fused KCl, we found that the damped oscillation of the disc gave olgarithmic decrement to satisfy the condition for measuring viscosity, and the precision of measurement was found adequate with thin fluid whose number of oscillations (n) is given 20,...,50 between the initial torsion angle of 90° and the final torsion angle of 10°. The relation between the number of oscillation (n) and the viscosity (71) is shown by the following equation. 2.915/(n-l) = 1.ox10- 2 (71p) 1l 2 -3.3x10- 4 ( 71p)+l.3x10- 5 ( 71p) 3l 2 (5) where p is the density of fluid measured by the platinum sinker method. 3. Results The variation in viscosity with both temperature and molar composition for the systems KCl-LiCl and KCl-NaCl are shown in tables 1 and 2. The isotherms of viscosity and molar volume of these systems plotted against molar fraction of KCl in the mixture are shown in Fig. 2 and 3, together with activation energy for viscous flow. The Viscosity of the Fused Salts Mixtures 407 Table I. Viscosity and activation energy for viscous flow of KCI-LiCL system. Composition Activation energy for viscous (mo!%) Temperature Viscosity flow calc. with eq. (4) KC! I LiCI (QC) (centi poise) (Kcal/mo!.) 835 1.21 100 0 5.55 790 1.37 850 1.16 80 20 810 1.23 3.75 790 1.27 I I 830 1.15 I 60 40 810 1.23 2.88 790 1.27 830 1.15 41 59 810 1.19 3.09 790 1.23 810 1.15 30 70 790 1.19 3.16 690 1.44 810 1.17 0 100 790 1.21 3.50 742 1.30 Table 2. Viscosity and the activation energy for viscous flow of KCI-NaCI system. Composition ___ --- -~--Activation energy for viscous (mo!%) Temperature Viscosity flow calc. with eq. (4) KC! I NaCl (QC) (centi poise) (Kcal/mo!) 835 1.21 100 0 5.55 790 1.37 791 1.03 79 21 766 1.13 8.88 727 1.40 787 1.03 59 41 760 1.12 8.57 719 1.39 786 1.02 35 56 762 1.12 9.06 720 1.38 786 I.OJ 27 73 764 8.26 1.11 -845 0 100 829 1.02 13.25 1.12 4o8 Yoshitaka MATSUMURA, Masao MIZUNO and Kiyokado NISHIHARA ..... 0 ~ c 6.0 0 ~ 5.0 ~ Ii i 4.0 .§ 3.0 g n 2.0 ct ..... 1.40 CD u, "&. 0 1.30 >, 'i 1.20 0 0 .!!! > 50 I IO 5 40 .... 0 > e 30 0 ~ -------~--. __ ---------------------- -----------. __ ....__ ....__ 0 20 40 60 80 LiCI (mo1%) Fig. 2. Molar vol7me, viscosity and acti-vation energy for viscous flow of KCl-LiCl system. IQ0 t; 5.0 ct 1.4 --CD .ig 1.3 0. (.) 1.2 >, :~ I. I 790°C [ 0 -~ > 1.0 0 E _,-E 0 0 > ... 0 0 ~ 50 40 30-0 20 40 60 80 NaCl (mol%) Fig. 3. Molar volume, viscosity and acti-vation energy for viscous flow of KCI-NaCI system. IC>0 The isotherms of viscosity of KCl-LiCl system decrease with increasing LiCl m the mixture and a minimum value of viscosity was found at 68 mol % LiCl. The activation energy for viscous flow showed negative deviation from additivity and a minimum value was found in the range of 55,-...,60 mol % LiCl. The isotherms of viscosity against molar composition for the system KCl-NaCl showed negative deviation from additivity and a minimum value of viscosity was found at 70 mol % NaCl. The value of activation energy for viscous flow showed positive deviation from additivity in the range of 0,-...,4Q mol % NaCl and showed negative deviation in the range of 40,-...,J00 mol % NaCl. The Fiscosity of the Fused Salts Mixtures 409 4. Discussion The phase diagrams for these systems91 indicate the simple eutectics. There is no evidence for the formation of complex ion in these systems10), and the molar volume of mixtures indicate a good agreement with the additivity of molar com-positions. In these systems, since there are two types of molecules in a mixture, we consider that the deviation of the activation energy for viscous flow from additivity is caused by the interaction between different types of molecules. We consider a number of different encounters of a mixture, which consists of molecules of types A and B, (in these systems they are ion pairs of K +cl-, Li+Cl-and Na+Cl-) some of which are shown in Fig. 411J. 000 & 000 0 0 0 0-&& 0 0 0 a e 0 0-0 f b 0 0-0 g C d 0 0-0 h Fig. 4. The type of viscosity interaction in a binary mixture (three body model) The types of intersaction considered in these cases are only three bodied and are all in one plane. The type of interaction shown in Fig. 4(a) would correspond to the activation energy EA, that is, for pure component A, the interaction 4 (h) would correspond to the activation energy E8 , that is, for pure component B, interactions of types (b), ( c) and ( d) all correspond to two molecules of type A and 410 Yoshitaka MATSUMURA, Masao M1zuNotand Kiyokado N1sHIHARA one of type B. One would expect the activation energy of types ( c) and ( d) to be identical. They will be referd to as E AAB, the activation energy for interaction (b) will be referd to as EABA· The interactions of types (f), (g) and (e) all correspond to one molecule of type A and two of type B, and activation energy for types (f) and (g) would be equal and designated by EABB' whereas type (e) may designated by EBAB" In any binary mixture of mol fraction x1 the fraction of type (a) in total oc-currences would be xf, as long as the number of molecules of type A and B are distributed at random in the liquid. Corresponding occurrences of the various type of interactions are listed in table 3; Table 3. Type of interaction and its fraction of total occurrences. Type of interaction A-A-A I A-B-A I A-A-B B-A-B I A-B-B I B-B-B B-A-A B-B-A Fraction of total occur-xf I xix2 I 2xix2 X14 I 2X1X~ x3 rences 2 Acitvation energy for I EA I EABA I EAAB I EBAB I EABB EB viscous flow The assumption made here of course is that probability for the interaction is dependent only on the concentration and not on the activation energy for viscous flow. It may be assumed that an activation energy for viscous flow in mixture may be shown as follows; Two additional assumptions are made at this point; EA= (EABA+2EAAB)/3, EB= (EBAB+2EABB)/3 · From these assumptions equation (6) can be written as; ( 7 ) We calculated the activation energy for viscous flow in the systems with Eq. (7) and from additivity of molar compositions. Similarly using experimental data, the activation energy was calculated with Eq. (4). The results are shown in Table 4 and 5. The Viscosi!)! of the Fused Salts Mixtures 411 Table 4. Activation energy for viscous flow of KCI-LiCI system. mol fraction calc. from additivity calc. with eq. (7) calc. with eq. (4) KCI I LiCI (Kcal/mo!) (Kcal/mo!) (Kcal/mo!) 1.00 0.00 5.55 5.55 5.55 0.80 0.20 5.15 3.75 3.75 0.60 0.40 4.75 2.98 2.88 0.41 0.59 4.32 3.03 3.09 0.30 0.70 4.08 3.16 3.16 0.00 1.00 3.50 3.50 3.50 Table 5. Activation energy for viscous flow of KCI-NaCI system. mo! fraction calc. from additivity calc. with eq. (7) calc. with eq. (4) KCI NaCl (Kcal/mo!) (Kcal/mo!) . (Kcal/mo!) 1.00 0.00 5.55 5.55 5.55 0.79 0.21 7.08 8.88 8.88 0.59 0.41 9.50 8.48 8.57 0.35 0.65 10.53 8.08 8.06 0.27 0.73 11.20 8.26 8.26 0.00 1.00 13.25 13.25 13.25 It can easily be seen that the values calculated with Eq. (7) are all in close agreement with those calculated with Eq. (4). It may be therefore concluded that, the deviation of the values of activation energy for viscous flow from additivity of the molar compositions are caused by the interaction between different types of moleucles or ion pairs in the liquid mixture. 5. Summary We measured the viscosity of KCl-LiCl and KCl-NaCl systems by the damped oscillation method with platinum disc. In the KCl-LiCl system, the isotherms of viscosity against molar compositions showed negative deviation from additivity and a minimum value of viscosity was found at 68 mol % LiCl. The aC;tivation energy for viscous flow showed negative deviation from additivity. In the KCl-NaCl system, the isotherms of viscosity against molar compositions showed negative deviation from additivity and a minimum value of viscosity was found at 70 mol % NaCl. The activation energy showed positive deviation from additivity in the range of o,..._,40 mol % NaCl and showed negative deviation in the range of 40,...._,J00 mol % NaCl. These deviations are caused by the interaction between different types of 412 Yoshitaka MATSUMURA, Masao MIZUNO and Kiyokado NISHIHARA molecules or ion pairs in the liquid mixture, and the activation energy for viscous flow of fused KCl-LiCl and KCl-NaCl mixtures may be represented by Eq. (7). References 1) J. Kendall, Medd. Ventenskapskad. Nobelinst., 2, 25 (1953). 2) E. Heymann & H. Bloom, Proc. Roy. Soc., 100, 11 (1953). 3) · J. Frenkel, "Kinetic Theory of Liquids" Dover, (1955). 4) B.F. Markov & K. Delimarskii, "Electrochemistry of Fused Salts" The Sigma Press, (1961). 5) J.O.M. Bockris, Proc. Roy. Soc., 226A, 423 (1954). 6) B.S. Harrap & E. Heymann, Trans. Faraday Soc., 50, 268 (1954). 7) H. Eyring & S. Glasstone, "The Theory of Rate Processes" McGraw-Hill, (1941). 8) W.D. Kingery, "Property Measurements at High Temperatures" John Wiley & Sons, (1941). 9) E. Elchardus & P. Laffitte, Bull. Soc. Chim. France, 51, 1572, (1932). 10) J.O.M. Bockris, "Modern Aspects of Electrochemistry" No. 2 Butterworth Scientific, (1956). 11) R.A. McAllister, A.I.Ch.E. Journal, 6, 427 (1960). 

The Viscosity of the Fused Salts Mixtures : KCl-LiCl and KCl-NaCl Systems

https://repository.kulib.kyoto-u.ac.jp/dspace/bitstream/2433/280671/1/mfeku_28_4_404.pdf

The Viscosity of the Fused Salts Mixtures : KCl-LiCl and KCl-NaCl Systems

Abstract

Similar works

Full text

Available Versions

Kyoto University Research Information Repository