Potential Measurements of Reactive Metal Chlorides in Alkali Halide Solutions: II . Chromium

Abstract

The thermodynamic properties of the dilute solutions of the chromium chlorides were determined in the solvents NaC1, KC1, CsC1, or their equimolar mixtures between approximately 973 and 1173 K using an EMF technique. Galvanic and redox cells with Ag-AgC1 reference electrodes were used. The cells are described by (-)Cr/CrC12 -AC1//asbestos diaphragm//AgC1 -AC1/Ag(+) and (-)Ag/AgC1 -AC1//asbestos diaphragm//CrC12 -CrCI~ -AC1/Pt(+) where AC1 represents the alkali chloride solvent. The thermodynamic properties imply high]y nonideal systems in which the formation of complex species is indicated. A reacting system consisting of Cr metal immersed in a CrC13-KC1 solution was studied potentiometrically. It was found that when the redox reactions were completed, all potentials assume a common value. This potential could be calculated using a simple mass balance and the formal potential for Cr/Cr 2+ and Cr2+/ Cr 3 § systems determined in this study.

Preparation of Titanium Deposit in Chloride Melts

“…[13,14] The electrochemistry of titanium dichloride in molten salts and the deposition of metallic titanium from titanium chlorides have been the subject of many investigations. [15][16][17][18][19][20][21][22][23][24][25] Therefore, as part of our USTB process, in which titanium ion from the anode dissolution of titanium oxycarbide in molten salts will electrodeposit in the cathode, the electrokinetic parameters of cathodic deposition such as current density, and initial titanium ion concentration could affect the morphology and purity of titanium deposit.…”

Electrochemical redox reactions of chromium and iron ions in molten NaCl–2CsCl eutectic for pyro-reprocessing of nuclear fuels

“…The temperature dependency of the NaCl-2CsCl system is larger than those in other molten chlorides, such as LiCl-KCl, NaCl, KCl, CsCl, NaCl-KCl, NaCl-CsCl and KCl-CsCl, [7,9]. This tendency of NaCl-2CsCl melts is common for U 4þ jU 3þ and Eu 3þ jEu 2þ couples in chloride melts [14,15].…”

“…There have been some published studies of the electrochemical properties of Cr ions in the context of Cr refining. Electrochemically determined redox potentials of the Cr 3þ jCr 2þ couple in LiCl-KCl [3][4][5], NaCl-KCl [6,7] and CaCl 2 -NaCl melts [7,8] were reported. Smirnov et al [9] determined the formal redox potential of the Cr 3þ jCr 2þ couple, E 0 Cr 3þ jCr 2þ , by the spectroelectrochemical method in various alkaline metal chlorides.…”

Thermodynamic Assessment of CrCl2 with NaCl–KCl–MgCl2–UCl3–UCl4 for Molten Chloride Reactor Corrosion Modeling

“…We have created a first-time thermodynamic assessment of the NaCl−KCl−CrCl 2 pseudo-ternary system from the available phase equilibria of Seifert and Klatyk, 15 Shiloff, 13 Kanno et al, 14 Gut and Gnehm, 16 and Belorukova et al 61 and the EM data of dilute CrCl 2 in KCl and in a NaCl−KCl eutectic from Tumidajski and Flengas. 62 The experimental data are used together with our estimations of Δ mix H for the NaCl−CrCl 2 and KCl−CrCl 2 systems, which follow the method described by Schorne-Pinto et al 63 The pseudo-binary subsystems contain the intermediate compounds Na 2 CrCl 4 , 14,64 K 2 CrCl 4 , 15 and KCrCl 3 15 for which S 298 °is not available, nor is Δ f H 298 °available for Na 2 CrCl 4 . Thus, the pseudo-ternary representation has a minimum of eight DOF associated with the MQMQA interaction parameters and liquid SNN coordination number ratio for each pseudo-binary subsystem, S 298 °for the three intermediate compounds, and Δ f H 298 °for Na 2 CrCl 4 .…”