By the straightforward extension of a general theory about nuclear quadrupolar spin-lattice relaxation in monatomic liquids, the relaxation rate R_{Q, a} for an a ion in a simple uniunivalent ionic melt was expressed in terms of the local electric field gradients (EFG) which originate from unlike or like charges external to the ion of interest and fluctuate via monatomic motion. The numerical calculations of R_{Q, a} have been carried out for ²³Na in molten NaCI, ¹³³Cs in molten CsI and ⁶³Cu in molten CuCI. The theory for R_{Q, a} of uni-univ alent ionic melts of NaCI and CsI was in agreement with the experimental results, whereas their values drastically depended on the materials. An argument for R_{Q, Cu} of ⁶³Cu in molten CuCl suggests that the substance is a partially covalent melt in which several Cl- ions can associate with one Cu+ ion in the form [Cu+(Cl-)n] ^(n-1) Dependence of ⁷Li, ²³Na, ⁶³Cu spin-lattice relaxation rates R₁ on temperature for ionic melts constructed of monatomic cations and complex anions may originate from a stochastic reorrientation around the three fold -axis of coinplex anion. Apparent activation energies ΔE_app of R_{1, a} for ⁷Li in molten LiNO₃ and ²³Na in molten NaNO₃ are 9.7 and 8.1 kJ/mol, respectively. It is iworth while showing that ΔE_app for ⁶³Cu in molten CuCl is equal to 7.5 kJ/mol and ΔE_app of ²³No in molten NaCl is equ al to zero. The ratio of EFG of ²³Na in NaNO₃ to that of ⁷Li in LiNO₃ is roughly estimated as four at the same temperature. Hence one expects EFG increases as atomic number Z increases.

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The spin lattice relaxation time (T₁) of ¹⁹F and ⁷Li nuclear spins in solid and liquid phases, of lithium tetrafluoroberyllate (Li₂BeF₄) was measured at the frequencies of 10 Mc and 20 Mc by means of the pulse NMR technique. The nuclear resonance absorption signals were also obtained by use of a single coil spectrometer.
As shown in Fig.2, T₁ in soli d phase decreased exponentially with increasing the temperature dependence of T₁ of ⁷Li may be attributable to the diffusion of Li nuclei with an activation energy of 12.8 kcal/mol; T₁ of ¹⁹F can be explained by the intermolecular dipole-dipole interaction modulated by the rotational diffusion of [BeF₄]^2- ions with an activation energy of 28.4 kcal/mol.
T₁ in liquid phase is shown in Fig.8. For ¹⁹F T₁ goes through a minimum at about 530° and T₁^-1 can be expressed as τ(1+ω₁τ₂) in terms of the correlation time τ. τ is estimated to be 5×10^-16 exp (24.8/RT) s. The behaviour of T₁ is attributed to the dissociation of F ions from complex ions and the long distance diffusion of F ions in liquid.
The absorption shapes of ¹⁹F below and above the melting temp erature have almost the same width of about 1 5 Gauss, which is much larger than the inhomogeneous width of about 0.4Gauss. It is concluded that molecular reorientation of [BeF₄]^2- ions takes place in liquid state as well as in solid state and that in liquid state molecular translational motion is not so fast as to narrow extremely the absorption line.

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The SiKα and AIKα spectra in the ternary glasses of the systems Na₂O-B₂O₃-Al₂O₃, Na₂O- B₂O₃-SiO₂ and Na₂O-Si02-Al₂O₃ have been studied as a function of the basicity of these glassesi
The SiKα energies were smaller in the glasses with higher basicity as was already seen in the binary silicate glasses. The energy-basicity relation of AlKα had the same tendency as that SiKα but changed drastically with the basicity, especially in the acidic region of the sodium alUmlnoborate glasses. The characteristic behavior of aluminium in the glasses could -be interprefed through the relative strength of the basicity of aluminium oxide to the other oxide s in the glasses.
The energy changes were also related to the fact that the polarity of Si-O and Al-O bonds decreased with iricreasing basicity. Thus it is concluded that one of the factors which govern the basicity is the electron density (effective charge) on the individual element in the glasses. It is also stressed that the basicity scale is useful for the understanding of the micro- and.. macroscopic properties in these oxide media. X-ray Fluorescence Spectro

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The coordination numbers of cations are usually not more than 4 in oxide glasses such as GeO₂, SiO₂, As₂O₃, P₂O₅, B₂O₃, and so on. Though V₂O₅ crystals have a layer structure consisted of VO₅ pyramids, V₂O₅ is successfully transformed into a noncrystalline solid from the melt by use of the splat-quenching technique. Therefore, it is significant to examine the coodination number of the vanadium atoms in molten V₂O₅.
The EXAFS (extended X-ray absorption fine structu re) of the vanadium atoms above its K-absorption edge has been measured for molten V₂O₅ at 750°C using the crystalline V₂O₅ as a reference material. By the Fourier transform, the V-O bond lengthes were determined to be 1.60 and 1.90Å in crystalline state and 1.80Å in molten state. The results of the former were in good agreements with those obtained through the crystal structure analysis. The coodination number, bond length, and Debye-Waller factor in molten state were further examined by least-squares calculation, using the coefficients of the phase shift and amplitude functions estimated from EXAFS spectrum of the crystal. By the parameter fitting method, the V-O bond length was determined to be 1.818±0.003Å and the coordination number of the vanadium atoms was found to be 4.8±0.2.
On the other hand, the mean V-O bond length and the coodination number of the vanadium atoms are 1.828Å and 5.0 in the crystal, respectively. The results of EXAFS analysis showed that the values in the melt are close to those in the crystal.

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With a main aim of elucidating the configuration of SiO₂ melt, molecular dynamics simulation (MD) was performed using the pair potentials The MD was carried out independently for Systems ( I ), (II) and (III), in which the number of particles in the basic cell was 300, 324 and 600, respectively. A very viscous liquid state was reproduced at 2000 K in ( I ) and (III). The self-diffusion coefficients in ( II ) were much smaller than in ( I ) and (III). This suggests that time evolution of 2.5 ps following an equilibrating stage of 10 ps order at much higher temperatures may be too short to obtain properties at the equilibrium state for this viscous melt. Nevertheless, as far as the structural feature was concerned, these systems were similar to each other: The interference function derived from the present MD simulation at 2000 K was in good. agreement with that obtained by X-ray diffraction of SiO₂ melt by Waseda and Toguri. Pair correlation functions, X-ray weighted radial distribution functions and angular correlation functions have been derived and discussed. The number of formed irreducible rings is counted and an instantaneous stereoscopic view is shown.

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The structures of molten system (LiCl)x-(CaCl₂)1-x, with x=1, 2/3, 1/2, and 0, and K₂2BaCl₄ have been investigated by X-ray diffraction analysis. In molten CaCl₂, the obtained nearest neighbour distances and coodination numbers are close to those found in the crystalline form, and are consistent with the abnormally small volume expansion ΔVf/Vs(=0.9%) behavior on melting. In molten Li₂CaCl₄ and LiCaCl₃, the nearest neighbour coodination number ncaici is similar to that found in molten LiCl and/or CaCl₂. In addition, over the whole range of concentration the nearest neighbour distance rci-ci appears an additivity as follows These behaviors for molten LiCI-CaCl₂ system are a result of the strong Coulombic attraction between Li+ or Ca2+ and Cl-. Our results for molten mixtures do not give the evidence of the existence of some complex ionic models previously proposed.

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Molten zinc chloride is a highly viscous liquid with an abnormally low electrical conductivity. Mackenzie and Murphy suggested that molten zinc chloride are composed of an associated liquid, with a low degree of association. Many workers observed an inflection temperature for this molten zinc chloride. The inflection temperatures were reported at 454°C and 354°C in viscosity, at 352°C in specific conductances, at 366°C in surface tensions and at 370°C in densities. Therefore, the authors tried to detect any difference in the structure of molten zinc chloride at three different temperatures, 330, 430 and 530°C.
The analyses of radial distribution functions (RDF) indicated that the nearest Zn-Cl distance and coordination number around the Zn atom in the molten ZnCl₂ are 2.30 A and 4.0, respectively, for all temperatures studied (330, 430 and 530°C). The whole distribution of Cl atom in the melts was quite similar to that of the closest packing arrangement. Accordingly, a loosely distorted ZnCl crystal structure (α-, β- orγ-type), composed of a corner shared tetrahedral units [ZnCl₄], was supposed as liquid ZnCl₂ model. Since the proposed three crystalline structures of α, β and γ phase resemble each other so much, that no particular one could be chosen as the mother structure of the liquid ZnCl₂.

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The results of X-ray and neutron diffraction experiments on molten alkali halides in which some data of our experiments by X-ray diffraction such as those of molten LiCl, NaCl, KCl, LiBr and KBr are included were summarized. The first peak positions in the radial distribution function in molten alkali halides by X-ray or neutron diffraction experiments are always longer than those by computer simulations and the differences of 0.1∼0.3Å exceed the experimental error. It seems to be due to the deformation of the electron shell. In the computer simulation, the shell model which has the spherical deformation was expected to have more closer value of the first peak position to the experimental one than the rigid ion model by taking the polarization of ions. However, no change in the first peak position was found. Therefore, the non-spherical deformation of electron shell at the point where ions are in contact with each other has to be taken into account. The neutron diffraction method with isotopic substitution has a merit of getting the partial correlation functions which are difficult to be obtained by the ordinary X-ray diffraction method and can compare directly with the results by the computer simulation. However, results of some molten salts such as KCl and CsCl by the neutron diffraction method with isotopic substitution have significant errors and there are something left to be improved for accuracy in measurements or correction of data in this method.

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The molar volume of molten salts, Vm at the melting point, Tm, were analyzed using the following parameters; electronic polarizability αt, the ratio of the charge and radius and the theoretical molar volume Vt, obtained by assuming the closed packing of ions. In single and binary molten salts such as alkali halides and alkaline earth halides except beryllium and magnesium salts having complex anions, the reduced molar volumes Y= Vm/∑Vt lie on a single curve against X=In[∑(_??_)3⋅(∑α)^4/3] within the error of ±10% (Figs.6 and 7). For the molten salts with complex anions, it is necessary to obtain further information on the effective volume and the electronic polarizability of the complex ions for the estimation of the density.

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Molar volumes of alkali thiocyanates in the molten state were measured by dilatometry, and represented by the empirical formulas as a function of temperature using the least square method. The results are shown in Table 2.
Refractive indices of these molten salts were also measured with the lights of 8 waveleng ths, and represented by Cauchy's approximate equations as a function of wavelength and temperature using the least square method. The results are shown in Table 4. Therefore, the electronic polarizabilities of ions in the melts were calculated from the refractive indices at infinite wavelength on the basis of the electronic polarizability of Li+ ion in the crystal obtained by Pauling. The temperature dependences of the electronic polarizabilities of these ions in the thiocyanate melts are shown in Fig.8, together with those of the ions in the nitrate melts.

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When the mixed molten salts are used, it is essential to know the melting points of their multi component systems. So, the phase diagram of ternary PrCl₃-CaCl₂-NaCl system was determined on the basis of three kinds of the binary systems of PrCl₃-NaCl, PrCl₃-CaCl₂, and CaCh-NaCl, and twelve kinds of the quasi binary systems of NaCl⋅CaCl₂-PrCl₃.
PrCl₃ was prepared by the chlorination of Pr₆O₁₁ with NH₄Cl and subsequently purified by sublimation. Resultant PrCl₃ was 99.9% up in purity. Reagent grade of NaCl and CaCl₂were thoroughly demoistened by heating at temperatures right below their melting points under vacuum for ca. 8h.
The phase diagrams w ere determined by the DTA method with an X-Y recorder on the basis of cooling curves of the molten salts under purified Ar atmosphere, wherein the cooling rates were about 10°C/min at 800°C and 6°C/min at 500°C.
The peritectic compound of NaCl⋅3 PrCl₃ so far unknown was found in the binary NaClPrCls system, whose peritectic point was 587°C. The ternary PrCl₃-CaCL-NaCl phase diagram had a eutectic and a peritectic point; the former was 440°C at 20-30-50 (PrCls-CaCl₂-NaCl)mol%, the latter 587°C at 36-50-14 mol%.

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The self-diffusion coefficients and their temperature dependences of sodium and fluorine in molten NaBeF₃ have been measured by the capillary reservoir method using ²⁴Na and ¹⁸F as; tracers, respectively. The observed diffusion coefficients (m2/s) were written as follows:
The diffusion mechanism of alkali and fluoride ions in the alkali fluoride-beryllium fluoride mixture in molten state were deduced by comparison of the self-diffusion coefficients of cations and anions in NaF-BeF₂ and LiF-BeF₂ mixtures with those in typical molten salts and molten silicates; the alkalline ions in the alkali fluoride-beryllium fluoride mixture diffuse by a similar mechanism to that in typical salts, while the fluoride ions diffuse by exchange between neighceIrring beryllate units via the rotation of large beryllate anions.

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Viscosities of molten alkali chloride* have been measured by means of newly designed capillary viscometer made of fused quartz as shown in Fig.1 and combined with, a special transparent electric furnace which can be inverted. The viscometer was of a suspended level type and designed so as to minimize the error associated with the measurement, e. g., the effect of surface tension. Reynolds number of the capillary was less than 100. The sample was introduced into the viscometer through the quartz filter and then sealed under vacuum.
Cell constants of the viscometer were determined by using distilled water as a calibration liquid. E;; ux times were measured by direct visual observation using a digital stopwatch, and showed excellent reproducibility. The viscometer in the present investigation proved to be very precise and the errors accompanied were considered to be less than 0.7%.
Viscosities obtained are collected in Table 1 and Figs.3-1∼3-5 togethe r with the previous data. Whereas the viscosity did not necessarily show any regularity, the activation energy for viscous flow increased with increasing cation size in the series of molten alkali chlorides. On the basis of a hard sphere model, the sizes of the flow units were considered to be nearly equal to those of cation-anion pairs. The viscosity of each molten alkali chloride at melting temperature increased with an increasing ratio of the flow unit volume to the hole volume.

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The thermal conductivities are estimated from data obtained by wave-front shearing interferomeiry using available. data on the density and the heat capacity. The thermal diffusiv ities and the thermal conductivities of molten KNO₃-NaNO₂ mixtures increase and decrea se slightly with a use of temperature depending on the molar ratio of KNO₃ to NaNO₂. They are expressed as linear functions of temperature as shown in Table 3. The results suggest th at the ionic melts containing the ions of smaller mass have the larger thermal conductivities. The thermal conductivities of the mixture melts deviate negatively from the additivity.
The validity of the proposed theories to the KNO₃-NaNO₂ system has been studied in which the effeets of mass, melting point, and density on thermal conductivity are taken into acc ount. The formula of heat transfer proposed by Rao is best applicable to the thermal conductivity of the mixture. Our result is well expressed by the following formula,
where K is the thermal conductivity, Tm, the molting point, pm the density at Tm, and M the mean mass (averaged molecular weight), while the constant is 2742 instead of 2090 according to Rao. Whereas the thermal conductivity of pure alkali nitrate correlates linearly with the ultrasonic sound velocity, this relation does not hold in the molten KNO₃-NaNO₂ mixtu re. The additivity rule can be applied to the sound velocity, but not to the thermal conductivity owing toits excess conductivity.

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An uni-temperature wall type condiction calorimeter was designed and applied to measure the heat of fusion and, heat capacity of the inorganic salts at elevated temperatures. Using the known heat capacity of lithium fluoride as a standard, the heat of fusion and the heat capacitY of titled salts were measured. Results obtained were as follows; the heat of fusion, ΔHm, for the Li/Na/K nitrate, carbonate, flouride, chloride, and sulfate eutectic were 11.9, 27.4, 17.1, 8.8₂ and 11∼12 kJ⋅mol^-1 and the molar heat capacity, C^p.m, were 140, 184, 76.3, 95.5 and 258/kJ⋅mol^-1K⋅^-1, respectively, These data were discussed comparing with that of single salts.

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The physical properties (density, surface tension, viscosity and electricL. conductivity) of Na₂O-Fe₂O₃ and CaO-Fe₂O₃ melts have been measured to find out the behavior of Fe³⁺-ion in these systems. The methods and a hand-made apparatus for the measurements are also de: scribed in detail. Since Fe₂O₃ is amphoteric oxide, it is assumed that the oxygen coordination number of Fe³⁺ is 4 and/or 6. Effects of N₂2O and CaO-content on the physical properties of ferrite, melts have been discussed in term of the change of oxygen coordination number of. Fe³⁺-ion. The parameters determining the behavior of Fe₂O₃ are the basicity of alkali (R₂O), alkaline earth (RO) oxide and the ratio of (R₂O, RO)/Fe₂O₃. In the Na₂O-Fe₂O₃ system, the maximum was: observed in the viscosity-composition curve at the composition corresponding to Na₂O/Fe₂O₃. This fact was explained by considering the change of Fe" complex anion size derived from the surface tension.

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An empirical approach was attempted to evaluate the real free energies of solvation of monoatomic cations in fused salts and the absolute electromotive forces got of the redox cou pies associated with the ions which are referred to the standard state of the gaseous electro n, where subscripts i and s denote an ion and a fused salt, respectively, and superscript 0 means the standard state.
The relative value for ion i and a definite reference ion j in the same solution have been expressed in terms of and the measured electromotive forces between the redox couples associated with ion i and ion j in the fused salt and in water, respectively, where zt is the valency of ion i.
It has been found that the value of estimated from the experimental values of and linearly changes with and that the gradient β is quite close to unity. The values of the chemical free energy of solvation have been estimated separately for 38 species of monoatomic cations in 10 fused salts, under the presumption that a hypothetical i on, which has no chemical interaction with any solvent, may exist in the extension of the strai ght line
The values of absolute electromotive forces for these ions have also been estimated using the values of assuming that the surface potentials of fused salts may be neglected because of the thermal agitation of the surface dipoles.

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The equilibrium calculation for the systems with multi components and multi phases consists of the followings. ( 1 ) Selection of the independent components. ( 2 ) The formulatio n for obtaining dependent components from independent ones and the mass equations for the chem ical reactions. The thermodynamic data such as the free energy change for the formatio n of each component and the activity coefficient of the components in each phase must be obtained as a function of temperature. ( 3 ) Mass balance equations. ( 4 ) Total mol of eac h phase is selected as the independent variable. ( 5 ) The Newton-Raphson method is applied for solving the equations which are obtained from items 3 and 4.
The above equilibrium calculation was applied to the syst e m of the carbothermic reduction of bauxite at high temperatures. Some results from the calcuation based on the therm odynamical data are shown. ( 1 ) Aluminium metal is difficult to be obtained from pure AlO₃ and pure carbon up to 2400 K. ( 2 ) Aluminium alloy containing about 60% of Al can be obtain ed from bauxite and the recovery of Al is only about 56% at 2400 K. ( 3 ) The amounts of iron oxide or silica which are necessary to reduce alumina perfectly are calculated and also the amount of heat required for the above reduction and the amount of carbon which supplies the heat for the combustion are obtained.

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In the previous studies the acid-base characters of binary oxide melts containing Na₂O as the basic partner have been investigated (Fig.1). The work was extended to the Na₂O-B₂O₃Al₂O₃ ternary system. The emf method of a concentration cell of the type;
The measurement was performed in the concentration range shown in Fig.2at ca.1150 K. The measurement of the emf as a function of temperature allows the evaluation of the partial molar free energy ΔG(Na₂O), entropy ΔS(Na₂O), and enthalpy ΔH(Na₂O), referred to the corresponding quantities in Na₂O.2 B₂O₃ shown in Fig.3∼5.
Al₂O₃ neutralizes Na₂O more strongly than B₂O₃ at the B₂O₃-rich side, while Al₂O₃ behaves like B₂O₃ in the other composition ranges covered in this work. Values of ΔG(Na₂O), ΔH(Na₂O), and ΔS(Na₂O) are consistent with the data of ¹¹B-NMR study, the electric conductivity measurement and so on. In conclusion, Al³⁺ is not less acidic than B³⁺ without solvent molecule like H₂O, which is contrary to amphoteric behavior of Al(OH)₃ in the aqueous solution.

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the optical basicity of Pb+ ion in fused potassium hydrogensulfate, which was calculated from the absorption energy due to ¹S₀→¹S₀ transition of Pb+ ion, increased as the temperature was raised up to 500°C, but decrrsed at 600°C. This fact is explained by the increase of the amount of potassium disulfate as the temperature was raised up to 500°C and by the formation of sulfur trioxide by decomposition of potassium disulfate at 600°C. Also, disso lving dichromium trioxide in the fused potassium hydrogensulfate, the optical basicity increased considerably as the temperature was raised from 500°C to 600°C. The increase of the optical basicity corresponds to the increase of chromium solubility from 183 ppm at 500°C to 3410 ppm at 600°C. This fact is elucidated by the following chemical equation in which dissolution of chromium oxide simultaneously forms potassium sulfate.
Chromium was dissolved as octahedral chromium(III) complex ion in fused potassium hydrogensulfate dissolving dichromium trioxide, of which optical was 0.53 at 500°C. When the optical basicity was higher than 0.53, tetrahedral chromium(III) complex ions were formed, and the two kinds of chromium(III) complex ions existed. Then, the amount of the tetrahedral chromium(III) complex ions increased as the optical basicity increased. As the optical basicity was 0.65, the amount of tetrahedral chromium= complex ions was four times that of the octahedral chromium(11l) complex ions. The octahedral chromium(III) complex salt was soluble in water, but the tetrahedral chromium(III) complex salt was insoluble. This complex salt had the composition of K₃Cr(SO₄)₃.

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Dissolution characteristics of vanadium(V) oxide(V₂O₅) and molybdenum(VI) oxide(MoO₃) in low-melting molten ammonium formate (HCOONH₄) and the related solvent systems such as [formamide (HCONH₂) + HCOONH₄], etc. were studied by measuring solubilities, visibl e absorption spectra and electron spin resonance spectra. Further, the feasibility of employing these solvent systems as a new electrodeposition bath was examined. It was found that HCOONH₄ is a good solvent for V₂O₅ and MoO₃, and CH₃COONH₄ is a poor solvent for them. HCONH₂, which is one of the decomposition products of HCOONH₄, was found to have excellent characteristics for the dissolution of these oxides.
V(V) in V₂O₅ was reduced to V(IV) with HC00- ion in HCOONH₄ at 120°C. The reduced V(IV) was considered to exist as vanadyl form complex anion which takes tetragonally di storted octahedral structure coordinated with HCOO- and HCONH₂. This estimation was deduced from the result that the V(IV) ion is easily removed on anion-exchange resins and the ion takes almost same g⊥ value of 1.974 as that of 1.981 for VO(H₂O)₅²⁺ ion, characterized by a strong V=O bond and five other weak VO bondings.
Mo(VI) in MoO₃ was reduced to Mo(V) and Mo(IV) in HCOONH₄ in a similar manner as the case of V₂O₅. This was a desirable behavior for the electrodeposition of Mo. Metallic Mo was electrodeposited from the [HCONH₂ + HCOONH₄ + MoO₃] system which was considered to be a model system of molten HCOONH₄ containing MoO₃.

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Solubilities of WO₃, MoO₃ and CrO₃ have been studied in AlCl₃-NaCl molten mixture. For the solubility measurement, a furnace with an apparatus which enabled the molten salt and the metal oxide to shake with a seesaw motion was used (ref. Fig.1 and Fig.2). As shown in Fig.4 and Fig.8, the solubilities of WO₃ and MoO₃ depended on the temperature and the concentration of AlCl₃ in the melt. From the results of X-ray diffraction patterns of the solidified melt and the colors of the melt or solidified melt, the following dissolving reactions were proposed.
2 AlCl₃ WO₃ = WOCl₄ + 2AlOCl
2 AlCl₃ MoO₃ = MoOCl₄ + 2 AIOCI
NaAlCl₄ MoO₃ = MoO₂Cl₂ AlOCl NaCl
CrO₃ reacted rapidly with the melt evolving fine bubbles, and solid product CrCl₃ was produced in the melt.

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The activity of oxide ion in a NaCl-KCl eutectic melt has been measured by the use of the galvanic cell with zirconia lime and mullite membranes. The calibration curves for the emf-ao_2-relation were obtained using sodium carbonate as the source of oxide ion. The effect of adding of oxoanion-containing salts on metallic corrosion was discussed with regard to the activity of oxide ion. The addition of sulfate ion to the melt had no effect on the activity of oxide ion, indicating that sulfate does not dissociate into SO₃ and O_2-. This means that sulfate ion does not function as an oxidizer for metallic corrosion. On the other hand, nitrate was found to dissociate according to the following reaction; NO₃-→NO₂+ + O_2-, The equilibrium constant of this reaction in the chloride melt was calculated from the activity of oxide ion and the corresponding standard enthalpy for the reaction was estimated to be 48Kcal/ion eq. Residual nitrate ion is expected to contribute to the cathodic reaction o f metal lic corrosion from the following reaction scheme;

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The oxide ion concentration in NaC1-ZnCl₂ molten salt can be determined by measuring the emf of the following cell,
Na(Mo)/β-Alumina/Na+, O^2- (in melt)/Stabilized Zirconia/O₂(Pt)and the emf of the cell is expressed as follows:
E=3.33-0.06 0 log [O^2-]at 360°C, when air is used as a positive electrode active mass. From this relation and other experimental data, the equilibrium constants of the reactions,
H₂O + 2Cl- = O^2- + 2 HCl (K₁), 2OH- = O^2-+H₂0 (K₂), were determined as follows:
K₁ =1.91 x10^-7 (atm), K₂=6.4×10^-1 (atm), respectively.
The minimization of the corrosion of the non-carbon anode may be achieved by the application of the oxide ion concentration measurement. The possibility was confirmed experimentally.

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Potential-pO^2- diagram for nickel, which is known to be corrosion-resistant material, in. the molten sodium hydroxide system at 623K (350°C) has been studied. The solubility product of nickel(II) oxide, K_SP, was determined to be 7.9×10^-15 by chemical analysis and also determined the standard electrode potential of Ni/NiO couple to be 0.73V vs. Na/Na+(for pO^2- =0), by the use of following cell:
Na/β-alurnina/NaOH(NiO saturated)/Ni
From the experiment, following conclusions were derived. ( 1 ) In this system, nickel is more electronegative than oxygen but is more electropositive than hydrogen, so nickel does not react with dissolved water in molten NaOH. ( 2 ) Corrosion-resistant property of nickel in this system is attributed to the formation of the protective film on the metal surface, since the solubility product of nickel is very small as compared with other metal oxides.
It is expected that the potential-pO^2- diagram will be of considerable us e in interpreting thermodynamic behavior of metals and for selecting materials to be used in this media. The same idea of constructing diagram shown here can be applied to other systems.

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The pyrolysis of phenol resins was studied in a molten bath as well as in an inert nitrogen atmosphere to examine the effects of heating rate and the maximum temperature on the evolved amounts of gas, le addition, the adaptability of molten salts for use as cracking media was eveluated.
The evolved amounts of gas in the pyrolysis of phenol resins increased with the elevation of the maximum, temperature within a certain temperature range. The evolved amounts of gad also increased with the increase of heating-rate, the upper limit of the evolved gas being dended onithe maximum temperature. The weight of char depends Only on maximum temperaturc.The weight ratio of gas to tar depends greatly on the heating rate. The evolved amounts of gas depend on the heating rate and the maximum temperature regardless of the properties of the gaseous media or molten salt. However, the use of molten salt bath as a.etadking medium is of greater advantage than gaseous media because of the high heat ccnductivity of molten salts

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Eutectic mixtures of Li0H, NaOH and KOH were selected as promising materials for latent iheat thermal energy strage devices because of their large heat of fusion and of low ma terial cost as described in a previous report (ref.10), and the eutectic points of LiOH-NaOH (30-70mol%), Li0H-KOH (29-71mol%) and NaOH-KOH (50-50mol%) were reported to be in an appropriate temperature range for thermal energy storage.
Experimental eveluations of thermal properties of th e eutectic mixtures were carried out by thermogravimetry (TG), differential thermal analysis (DTA) and differential scanning calorimetry (DSC), because heats of fusion have not been reported and thermal behaviors, such as supercooling, , have large effects on the performances of the thermal enegy storage equipments. The eutectic mixtures were dried and melted in an electric vacuum oven, and the thermal analyses were made by using a poly(tetrafluoroethylene)-coated aluminum sample container 'under the flow of nitrogen. The hydroxides, especially KOH, are highly hygroscop ic, and the residual water has effects on their thermal properties, such as transition points and heats f transition (Fig.1).
Every eutectic mixture shows little supercooling (Fig.4-6), and the eutectic points and heats of fusion for Li0H-NaOH LiOH-KOH and NaOH-KOH were 213.5°C, 330.J/g; 222°C, 184J/g and 165°C, 172J/g, respectively. If any devices are to be developed to overcome their cirawba, cks of hygroscopic and corrosive properties, these eutectic mixtures are very promi sing mat4rials for latent heat thermal enegy storage devices.

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In order to develop DSA type electrodes in molten salt systems, the electrocatalytic activity and stability of metal oxide electrodes have been investigated for a chlorine electrode r eaction in AlCl₃-NaCl melt at 175°C. Fifteen kinds of oxide electrodes (Table 1) including rutils, perovskites and a spinel have been examined. Thin films of those oxides were prepared by dip-coating and thermal decomposition methods on Pyrex glass substrates which were coated with highly conductive SnO₂ (Sb-doped) films prior to the deposition of catalyzers. The SnO₂ film works as a current collector and a catalyst support. The detailed construction of the oxide electrodes is shown in Fig.1. Fig. 4∼6 show Tafel curves on the various oxide electrodes for the chlorine electrode reaction in the melt of pCl=1.1 and P_Cl2= 1 atm. The exchange current densities are summarized in Table 2. These results reveal that noble metal oxides have high catalytic activity for the reaction. Especially, the RuO₂, Rh₂O₃ and IrO₂ electrodes are excellent materials with respect to both catalytic activity and stability, sustaining low and stable overpotentials for prolonged chlorine evolution, as shown in Fig.8. The PtOx and PdO electrodes were unstable in the melt. The catalytic activity of mixed ox ide electrodes such as RuO₂-TiO₂ and RuO₂-IrO₂ were examined as a function of RuO₂ content. In the cases of the RuO₂-Sn₂ and RuO₂-TiO₂ electrodes, the catalytic activity for the reaction changed considerably at 50mol% RuO₂ (Fig.11) and then the activity approached that of pure RuO₂ electrode. The catalytic activity of the RuO₂-IrO₂ electrode was simply dependent on the RuO₂ content (Fig.11), showing no synergic effect. The temperature dependence of the electrocatalytic activity on the ku02 and GC electrodes is shown in Fig.12. The exchange current density of the RuO₂ electrode at 175°C is about 10 times larger than that of the GC electrode, but both values become equal at 400°C. This phenomenon suggests that the electrocatalytic effect would not be expected at high temperatures (>400°C) in this system.

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Electrolysis of the soluble Nb anode was performed in the equimolar LiF-NaF-KF molten system at 550-650°C. The electrode processes were discussed from the results of the anodic dissolution of Nb, chronopotentiometry, cyclic voltammetry and potentiometry. The main equilibrium reaction was considered to be 2 Nb³⁺+Nb↔3 Nb²⁺ (1) at the lower concentration of 7.36×10^-4 mole ficaction, and at the higher concentration of 1.10×10^-3 mole fraction the equilibrium reaction, Nb⁵⁺+Nb↔Nb²⁺+Nb³⁺ (2), was predominating together with the disproportionation reaction of 3 Nb⁵⁺+Nb↔4Nb⁴⁺. The standard electrode potentials of _??_ and the equilibrium constant K for the reaction (1) were as follows:

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The electrochemical stablity of sintered nickel ferrite (Ni_xFe_3-xO₄, x-=0.16∼0.85) electrodes has been studied in the LiCl-KCl eutectic melt at 450°C. The electrochemical stability was increased as the nickel content x became higher. The background current of the Ni^0.85Fe^2.15O⁴ electrode was less than 100μA/cm2 in the potential range -0.2∼+-0.9V vs. Ag/AgCl (x=0.1) at the voltage scan rate of 0.1 V/s; the nickel ferrite electrode was more stable than the glassy carbon electrode which is usually used in a high temperature molten salt system.
The electrode reactions of Cu (II)/Cu(I) and Eu(III)/Eu(II) redox couples have been studied on the Ni^0.85Fe^2.15O⁴ electrode in the LiCl-KCl eutectic melt at 450°C. Both redox couples showed the diffusion-controlled reversible reaction on the nickel ferrite electrode. The electrode worked well qualitatively as well as quantitatively. It was found that the Ni^0.85Fe^2.15O⁴ could be used as an indicator electrode for an electrochemical study in the LiCl-KCl eutectic melt at the potential range -0.2∼-0.9V vs. Ag/AgCl (X = 0.1).

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The Al/FeS₂ cells have been investigated as a potential candidate for the advanced secondary cells for both load-leveling applications and electric vehicles. The cells have a molten salt electrolyte such as AlCl₃-NaCl or AlCl₃-NaCl-KCl and are operated at temperatures between 100∼250°C. Dendritic deposits are produced on the Al electrode from the bath upon ch arging. Various additives to the bath have been studied to obtain an adherent Al deposit. The most promising additive was 0.2mol% SnCl₂. Studies on the polarization curves, the overpotentialelectricity curves, and the surface of Al deposit indicated that the adherent deposit was obtained when the charge transfer step determined the cathodic reaction rate. The Al deposit becomes more smooth when the it of the reaction is larger and the activation energy is smaller.
Various additives to the FeS₂ electrode have been investigated to improve the utiliza tion of the active material and the cell voltage. Graphite and copper ion were the most effective. The porous FeS₂ electrode was also effective. Moreover, it was found that the compound such as Cu_xFe_1-xS₂ was one of the most promising cathode materials. The most suitable content of AlCl₃ in the molten salts bath was around 60mol%.

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The electrofluorination of dicyanodiamide [(NH₂CN)₂] on the anode was studied in a molten KH₂F₃ at 120°C. Amorphous carbon was used as the anode and Pt rod as the ref erence electrode. Anodic products were analyzed by both gas chromatography and infrared spectroscopy. The critical current density obtained by the potentiostatic method was increas ed with the increment of (NH₂CN)₂-concentration. In the presence of 1.0 wt% LiF in this electrolyte, anode effect did not occur below the current density of 1000 mA/cm2.
The anode gas was composed of N₂(+O₂), CF₄, NF₃, C₂F₆, N₂O, CO₂ and other substances. Besides, the substance trapped at 0°C was mainly cyanuric acid. And melam and/or melamlike substances were obtained as supernatant on surface of fluoride melts.
From these results, it is suggested that (NH₂CN)₂ would react ch emically with atomic fluorine produced by the discharge of fluoride ion and that the change of the C_m F_n, [(CF)_n-]I film on the anode to (CF)_n[(CF)_n-II] film was prevented. The mechanism of NF₃-formation in the melt is as follows;

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A single phase of the molten fluoride mixture is s imultaneously functionable as a nuclear reaction medium, a heat medium and a chemical processing medium. Applying this characteristics of molten salts, the single-fluid type accelerator molten-salt breeder (AMSB) concept was proposed, in which ⁷LiF-BeF₂-ThF₄ was served as a target-and-blanket salt (Fig.1 and Table 1), and the detailed discussion on the chemical aspects of AMSB are presented (Tables 2-4 and Fig.2). Qwing to the small total amount of radiowaste and the low concentr ations of each element in target salt, AMSB would be chemically managable.
The performance of the standard-type AMSB is improved by adding 0.3∼0.8m/o ²³³UF₄ as follows (Tables 1 and 4, and Figs.2 and 3): ( a ) this“high-gain”type AMSB is feasible to design chemically, in which still only small amount of radiowaste is included;( b ) the fissile, material production rate will be increased significantly;( c ) this target salt is straightly fed as an ²³³U additive to the fuel of molten-salt converter reactor (MSCR); ( d ) the dirty fuel salt suctioned from MSCR is batch-reprocessed in the safeguarded regional center, in which many AMSB are facilitated;( e ) the isolated ²³³UF₄ is blended in the target salt sent to many MSCRs, and the cleaned residual fertile salt is used as a diluent of AMSB salt; ( f ) this simple and rational thorium fuel breeding cycle system is also suitable for the nuclear nonproliferation and for the fabrication of smaller size power-stations.

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The⁷Li and ²³Na spin-lattice relaxation times, T₁, have been measured for molten LiAlCl₄ and NaAlCl₄ from the melting points up to 300°C. The magnitudes of T, for ⁷Li and ²³Na range from 10 to 20 s and from 20to 70 ms, respectively and increase with increasing temperptures. The ⁷Li and ²³Na spin-lattice relaxation rates (1/T₁) are attributed to quadrupolar relaxation via monatomic and complex-ionic motion. The ratios of the respective electric-fieldgradients, of ²³Na nucleus in molten NaAlCl₄ and NaNO₃ to each of 7Li nucleus in molten NaAlCl₄ and LiNO₃ are almost four at the same temperature: the ratio of the atomic n umber f Na to that of Li eauals eleven-thirds.

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The thermal conductivity data of molten salts just above the melting points are correlated with their mean ionic weights and found to be classified into three groups - salts of oxoacids, chlorides and the others. Semiempirical theories about the thermal conductivity of molten salts so far proposed are shown to be applicable to the first group extremely well but not to the other two.

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Interelectrode potential difference (U) of the non-isothermal molten salts thermochemical cell with Cu and Ni electrodes has been measured under the conditions of ΔT(=T_cu-T_ni)=±50-±-350°C at over 250°C in order to assess it's possibility as devices for the direct conversion of heat to electricity.

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