Voltaic Cells in Fused Salts: Part Iii. The System Silver – Silver Chloride, Cadmium – Cadmium Chloride

Abstract

PART 111. THE SYSTEM SILVER -SILVER CHLORIDE, CADMIUM -CADMIUM CHLORIDE'bsing a sil\.er-sil\.cr chloride reference electrode, the stantl.ird elrtctrocl-p-1tcnti:ll h-1s 11:-n establishetl for the eq~lilibriurn CdICd++ in melts containing ecl~rimolar cl~r~ntities of ICCI ancl NaCL. The csperirnerltally obtairietl stallclarcl potclitial \\.as greater than that calc~rlated from theoretical thermodynamic data. This difference was attributed to the formation of a cadmi~cm complex in the lnelt. A dissociation constant for thc co~nplex \\.as calc~rlatetl.The erfect of temperature on the electromotive force of the silver-caclrnium voltaic cell mas also mcas~rrecl, and the heat of the cell reactior~ mas calc~~lated from the data. To estcr~cl the ternperat~~re range of the cadnii~rm data, a catlrni~~m-lead alloy was ~~s e c l in the higher ternperatwe experiments. To correlate these data with those for the pure c a d m i~~r n systern, the act~vity coefficiel~ts of c a d m i~~n i in the alloy mere determined electromctrically using the silversilver chloride electrode as a reference. It was found that the activity coefficients were in agreement with previously publishecl data obtailled a t Iowrer temperatures usi~ig a purc cadmium reference electrode. The activity coefficients werc v i r t~~a l l y indepenclcnt of temperature but showed large positive deviations from unity whel~ thc mole fraction of c a t l m i~~n~ was decreased below about 0.8. INTIIODUCTIONParts I and I1 of this series (1, 2 ) described the development ancl use of a reversible silver -silver chloride reference electrode for determining the electromotive forces of voltaic cells in chloride melts a t high temperatures.In this paper, experiments will be clescribecl in nrhich the silver -silver chloride reference electrocle was used to study the cadmiunl -cadmium chloricle equilibria. An equi~nolar mixture of molten potassium and sodi~im chlorides was used as the colnlnoll solvent.These results are an additional contribution t o the current program of establishing electromotive series for metals in molten salts a t different temperatures.The technique used to studjr the Cd-Ag system was essentialll~ the same as that previously described (1). During the preliminary experimental a o r k it became apparent that because of the relatively high vapor pressure of moltell cadmium and the inflammability of cadmium vapor in air, a closed cell operating with an inert atmosphere ivould be required. The complete cell design is s h o n~i~ in Fig. I. The cell was constructed from silica tubing of 2 in. diameter and co~lsistecl of two sections connected by a ground silica joint. The upper section of the cell was closed with a cork stopper, into which were fitted the silver -silver chloride reference electrode, the thermocouple well, the feeding pipe with stirrer, and the gas inlet tube. The col-6 stopper was covered externally with Pyseal cement and then water-cooled to prevent the melting of the cement from the heat of the furnace. The inner surface of the cork stopper was ...

Electrode Potentials of the Uranium Chlorides in Fused Alkali Chloride Solutions

“…The magnitude of the equilibrium constant for reaction [4], shown in Table 11, indicates that in the presence of uranium metal, uranium tetrachloride woulcl be reduced quantitatively to the trichloride.…”

“…The equilibrium constants of reactions [l] to [3] indicate that uranium metal will displace silver ions from solution, and that a t equilibrium, the preclominant species will be uraniuin tetrachloricle.…”

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.…”

Electromotive Force Series of Metals in Fused Salts and Activities of Metal Chlorides in 1:1 Molar KCl-NaCl Solutions

“…In the initial experimental work, a thermodynamically reversible, diffusion-free, silver-silver chloride reference electrode (1) was developed. This electrode was used to obtain the standard potentials of several systems (2)(3)(4)(5). In this paper, the data have been used to establish emf series of metals at various temperatures.…”