Giuseppe A. Sacchetto

Standard electrode potentials of the iodine-iodide system in molten (Li,K)NO3

Summary The standard potentials of the redox couples involving I2, I−, and I3−, and the equilibrium constants of the reactions: I 2 ( g ) ⇌ I 2 ( soln ⁡ . ) I 2 ( g ) + I − ⇌ I 3 − in molten (Li,K)NO3 between 435 and 490°K, have been determined.

Vapour pressure of very concentrated electrolyte solutions I. Measurements on {(1 − x) H2O + xLiNO3} and {(1 − x) H2O + xNH4NO3} by a dew-point apparatus

The vapour pressure of water above {(1 − x )H 2 O + x LiNO 3 } and {(1 − x )H 2 O + x NH 4 NO 3 } has been determined from dew-point measurements in the approximate range 320 T/K x (LiNO 3 ) x (NH 4 NO 3 )

Ion-pair high-performance liquid chromatography of inorganic anions with photometric, conductometric and amperometric detection

Abstract The behaviour of various inorganic anions has been studied in a reversed-phase ion-pair high-performance liquid chromatographic system using aqueous mobile phases containing cetyltrimethylammonium bromide (cetrimide) as the ion-pairing agent, citrate as the counterion and methanol as the organic modifier. The results basically correspond to the theoretical model of dynamic ion exchange, but some significant deviations from the predicted dependences indicate that the actual separation mechanism is more complex. The detection methods involved d.c. and a.c. conductometry, amperometry with a carbon-fibre array working electrode and UV photometry at 210 nm and at the solute absorption maxima. Conductometry and UV photometry enable universal detection (some anions are, however, detected indirectly, from the negative response of the detector). Amperometry is selective for oxidizable anions. The detection limits for amperometry and UV photometry are similar, whereas conductometric detection is somewhat less sensitive.

Vapour pressures of very concentrated electrolyte solutions. IV: Measurements on {(1-x)(CH3)2SO+xKSCN} by a dew-point apparatus

Abstract The vapour pressure of water above {(1 − x)H2O + xKSCN} has been determined from dew-temperature measurements in the range 340 T K for 0.05

Ion association in molten salts. Quasi-lattice model for quaternary reciprocal systems

Summary The quasi-lattice treatment of ternary reciprocal systems of molten salts has been extended to quaternary systems of the type (A+, B+, C+, X−, Y−) dilute in A+ and X−. According to the model, the “apparent” association energy between A+ and X− in the mixed “solvent” BY+CY should be a non-linear function of the molar composition of the solvent, and a function of the temperature. The existing experimental data on ion association energies in mixed solvents appear to be insufficient to provide a conclusive test of these predictions.

Coulometric titrations with iodide ions in molten (Li, K)NO3

Summary Iodide ions were produced in molten (Li, K)NO3 with a 100% current efficiency by constant current reduction of solid silver iodide. This method was applied to the titrations of Ag(I), Hg(I), Hg(II), Cu(II), and Bi(III). The equivalence point was detected by potentiometric, bipotentiometric, and biamperometric techniques; the titration error was generally lower than 1.5%. The reaction between Cu(II) and iodide implies the reduction of copper to insoluble CuI and the evolution of iodine. Nitrate ions take part in the reaction between Bi(III) and iodide, acting both as a base and an oxidant.

Vapour pressures of very concentrated electrolyte solutions III. Measurements on [(1−x)(CH3)2SO + x{(1−y)NH4NO3 + yLiNO3}] by a dew-point apparatus

Abstract The vapour pressure of dimethylsulphoxide above very concentrated solutions of NH 4 NO 3 , LiNO 3 , and their binary mixtures in (CH 3 ) 2 SO have been determined from dew-point measurements in the approximate range 327 T K . The results are treated on the basis of the Stokes-Robinson adsorption-hydration theory, which is found to be applicable over wide ranges of solvent activity a s , extending from the lowest experimental values a s ≈ 0.2 to 0.3, up to at least a s = 0.6. The structural and energetic parameters involved in the above theory, calculated for (ammonium nitrate + dimethylsulphoxide) and for (lithium nitrate + dimethylsulphoxide) are compared with those previously obtained for (calcium nitrate + dimethylsulphoxide) and with those for (ammonium nitrate + water) and (lithium nitrate + water). The strong interactions revealed for both Li + and NH 4 + with (CH 3 ) 2 SO bring both cations into the group of strongly solvated cations in such a good donor solvent as (CH 3 ) 2 SO, in agreement with previous suggestions in the literature. The existence of a caging effect of all the three cations Ca 2+ , Li + , and NH 4 + by (CH 3 ) 2 SO molecules in the whole experimental composition range might be expected. The dependences of the parameters on the mole fraction y of the solute mixture {(1− y )NH 4 NO 3 + y LiNO 3 } are discussed in relation to the trends previously observed for similar aqueous solutions.

Standard potentials of the bromine-bromide and chlorine-chloride electrodes in molten (Li, K)NO3

Summary The standard potential of the bromine-bromide electrode in molten (Li, K)−NO3 between 410° and 550°K has been determined. The standard potential of the chlorine-chloride electrode in the same solvent, which cannot be determined experimentally, has been calculated from existing data.

Coulometric titrations with mercury (I) in molten (Li,K) NO3

Summary The titrations of halides, chromate and “oxide” ions in molten (Li, K)NO 3 with Hg(I), produced by constant current oxidation of mercury, have been studied. The titrations were followed by potentiometric, bipotentiometric and biamperometric techniques. The solubility products of mercurous iodide and mercurous chromate have been determined from e.m.f. measurements in the temperature range, 415–465°K.

Solubility products and related thermodynamic quantities of silver halides in molten (Li,K)NO3 from E.M.F. measurements

Summary The solubility products of silver halides in molten (Li,K) NO 3 and the related thermodynamic quantities have been determined from e.m.f. measurements, and are compared with previous data. The standard electrode potentials of the silversilver halide second-kind electrodes have also been computed.