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Florisil, alumina, and silicic acid were compared for the column chromatographic separation of lipids from chlorinated hydrocarbons. Alumina had the largest capacity per unit volume to retain lipids and oils (0.7 g beef lipid/ 25 g alumina) while eluting dieldrin. Florisil had a larger capacity than silicic acid. Deactivation and elution with a nonpolar solvent gave superior separation over previously used polar solvent elution from activated adsorbents. The effects of temperature, water, and lipid load on the elution of dieldrin were studied. A yellow dye, p-methoxyazobenzene, was found to have a slightly larger elution volume than dieldrin, and is useful as a visible reference material for the elution of chlorinated hydrocarbons.

Summary The basic electrochemical properties of an anodic film formed on platinum from oxide solutions in a lithium chloride-potassium chloride melt at around 430°C were investigated. In spite of the very different temperature and solvent system, very similar behaviour to the aqueous systems was found using galvanostatic, potentiostatic and e.m.f. decay transients. The anodic behaviour qualitatively supports the notion of a field assisted oxygen incorporation as the rate-determining step for film formation as suggested for aqueous systems. Film reduction occurred over a large potential range, which was ascribed to a large distribution of site energies within the oxide phase. The characteristic “film ageing” effects seen with aqueous systems were also observed. At higher anodic potentials under chronopotentiometric conditions, the reversible discharge of oxygen probably occurred on both platinum and gold electrodes.

By means of cathodic chronopotentiometric and potentiometric studies of (nominally) polysulphide solutions in LiClKCl eutectic at temperatures between 400 and 440°C, the predominant solute species present at concentrations around 10−2 M was shown to be polysulphide S2−x. This conclusion is in harmony with earlier spectral and electrochemical studies in LiClKCl eutectic. The chronopotentiometric oxidation of sulphide ion S2− in the same melt is rather complex, but it appears to be controlled by the extensive formation of a polymeric sulphur film, although a mixture of various soluble polysulphides is ultimately formed. Various detailed mechanisms that can account for the observed behaviour are discussed.

Chronopotentiometric and steady-state voltammetric techniques have been employed to study the electroreduction processes: Cr(III)+eCr(II) and Cr(II)+2eCr(0) separately, using the LiCl+KCl eutectic as solvent at 500°C. The adsorption of the ions on the electrode surfaces appears to play a role in the overall electrode processes; the degree of adsorption was correlated with the variation of exchange current density with concentration in the case of the Cr(II) ions. Fluoride ions had no effect on the electrode processes. The chronopotentiometric behaviour of Cr(III) ions was rather complex but adsorption appeared to play a part in this case also.

A review of corrosion in fused salts is presented During the last 20 years interest in high-temperature liquids has expanded rapidly following their use as electrolytes for the production of uranium in the Manhattan project. As a consequence the structure and properties of fused salts have been much investigated.1–;3 Fused salts have many possible practical applications; for example they have been proposed as nuclear reactor fuel-coolant systems, heat transfer liquids, and reaction media for both chemical4 and electrochemical processes.5 Increasing awareness of fused salts has also led to evidence for their presence in many high-temperature industrial processes. In all these systems corrosion is a major problem.

Half-wave potentials and diffusion coefficients for the reduction of PbII, CdII, NiII and CoII ions have been determined at a dropping mercury electrode (d.m.e.) in molten LiNO3+NaNO3+KNO3 eutectic at 145°C. The results are compared with those obtained previously by other authors. The discrepancies, where they exist, are related to the effects of appreciable quantities of water, arising from the use of incompletely dried solvents and solutes added as hydrates, and chloride ions present in the melts used in previous investigations.

A potentiometric technique has been used to indicate the formation of complexes between the cations Ni2+, Co2+, Pd2+, Pt2+ and Cu1+ and the anions Br− and CN− in the molten solvent LiClKCl. In some cases it has been possible to quantify the complex formation by deriving the appropriate stability constants from the experimental data.

An electrode of the third kind, responding to metal-ion concentration changes in alkali-metal nitrate melts, is described, and special features and difficulties attending its practical application are discussed. It has been employed to monitor the varying uncomplexed cadmium ion concentration during titrations of cadmium nitrate with potassium chloride and potassium bromide in molten equimolar NaNO3-KNO3 at 254°C. The resulting emf data were used to calculate the stability constants of the series of complex ions formed in each case. The coincidence of the log10F0/log10Cl plots evidences the absence of dinuclear complexes and the constancy of activity coefficients (corresponding to non-specific interactions) for the experimental conditions in these systems. The stability constants are discussed in relation to the co-ordination of cadmium ions in nitrate melts, with and without added halide ions, and the differences between the molten nitrate solvent and water.ab]|fr|Une electrode de 3eme espece, indicatrice de cation en milieu fondu de nitrate alcalin, est decrite et discutee quant a ses possibilites pratiques d'application. Elle a ete employee pour representer la variation de [Cd2+] non complexe au cours du titrage de Cd(NO3)2 par KCl et KBr, dans un melange equimoleculaire NaNO3-KNO3 fondu a 254°C. Les fem obtenues ont permis de calculer les constantes de stabilite d'une serie d'ions complexes ainsi engendres. On rend ainsi compte, en outre, de l'absence de complexes dinucleaires et de la constante des coefficients d'activite dans de telles conditions experimentales. Discussion des valeurs des constantes de stabilite selon la coordination des ions Cd2+ dans des nitrates fondus, avec ou sans participation d'ions halogenes. Comparaison a l'eau du solvant nitrate fondu.

Summary The dependence of the double-layer capacitance of the liquid metal/molten alkali halide interphase on potential and temperature is discussed. The effects of temperature, melt composition and electrode metal on the shapes of the capacitance/ potential curves are explained by considering a recent suggestion27 that these curves can be divided into ideally polarisable and ideally reversible regions. An equation is given for the temperature dependence of the potential at which the transition from ideally polarisable to ideally reversible behaviour occurs.

Summary The electroreduction of phosphates has been examined by voltammetry andchronopotentiometry in molten sodium trimetaphosphates and as solutions in sodium chloride-potassium chloride over the temperature range 400°–800°C. Three electroactive species, reducing at potentials more anodic than the solvent, were found by chronopotentiometry; these were identified as the ortho, pyro and tripoly-phosphate ions. The electroreduction appears to be that of pentavalent to trivalent phosphorus; the overall products probably result from further chemical reactions.

Phosphate glasses are known to be mixtures of chain phosphates. The presence of the lower polymers has been confirmed by electrochemical techniques and the proportions of the orthophosphate monomer in sodium metaphosphate melts have been estimated at temperatures between 660–810°C. The orthophosphate had not been detected in phosphate glasses using paper chromatography, but it is considered that quenching tends to increase polymerization and thus causes loss of the monomer.

Summary A term which accounts for dinuclear complex formation has been introduced into the previously published computer method for the calculation of stability constants from potentiometric data. This modified procedure has been used to reassess the magnitudes of the formation constants of silver halide dinuclear complexes in both nitrate and chloride melts. On this basis, the presence of dinuclear complexes in these melts, under the experimental conditions investigated up to now, is shown to be unlikely.

For the system formed by the addition of KBr to Cd(NO 3 ) 2 in liquid NaNO 3 -KNO 3 at 263°C, the relation of the square root of the transition time to the reciprocal of the current density shows two sections. Analysis of this behavior shows that Cd exists probably as CdBr 2 in solution under the given conditions and has a lifetime of about 0.3 sec.

Summary The electroanalytical technique, chronopotentiometry, has been employed to determine the interdiffusion coefficients of Ag+, Cu+, Pb2+, Cd2+, Co2+, Ni2+, Cu2+, Zn2+, In3+ and Bi3+ ions in molten Li2SO4−K2SO4 (80:20 wt.%). The data have been compared with similar data reported for molten LiCl−KCl (59:41 mole %) and correlations with functions involving charge numbers, ionization potentials and ionic radii established.

The exchange current density for the metal-molten salt system Ag/AgNO 3 , NaNO 3 -KNO 3 has been determined by the single pulse galvanostatic method in an apparatus which enables the evaluation of the double layer capacity and exchange current in one experimental set-up. The range of applicability of the single pulse galvanostatic method is less than that formerly estimated. A detailed analysis is given.

Transition times of electrode processes have been determined from cathode potential-time relations at constant current, at various concentrations, current densities and temperatures, in the following molten salt solutions: PbCl 2 in LiCl-KCl; AgNO 3 in NaNO 3 ; AgNO 3 + NaCl in NaNO 3 ; AgNO 3 in NaNO 3 -KNO 3 ; AgNO 3 + KCN in NaNO 3 -KNO 3 ; Pb(NO 3 ) 2 in NaNO 3 -KNO 3 ; PbCl 2 in NaNO 3 -KNO 3 ; Cd(NO 3 ) 2 in NaNO 3 -KNO 3 . In general, S and's equation for the transition time, in the case of mass transfer by semi-infinite linear diffusion, is obeyed. Diffusion coefficients, energies of activation for the diffusion processes and solubility products are calculated. Information concerning complex formation and the structure of molten salts is reported.

The maxima observed on d.c. polarograms, for some metal- and halide-ion solutions in these melts, have been investigated. These maxima do not in general resemble the classical kind, mainly observed in aqueous solutions. In this study, they are related to adsorption processes involving complex ions present in the bulk solution. The electrode processes may behave in an ideally reversible manner in the region of the maxima. A tentative explanation in terms of this model is also put forward.

Summary The results of potentiometric studies in molten lithium chloride-potassium chloride eutectic are reported. The potentials of gold and platinum electrodes were found to respond to variations in the oxide-ion concentration of the melt and to changes in the partial pressure of oxygen above the melt. These changes in potential did not obey the Nernst Equation for a reversible oxygen electrode. It is suggested that the potential-determining reaction is: 2 O 2 − + 2 e = O 2 2 −

The stability constants of the chloro- and bromo-complexes of NiII, CoII, CdII, and PbII have been determined in the LiNO33+NaNO3+KNO3 eutectic solvent at 145°C. Some preliminary experiments have also been carried out in melts containing fluoride and cyanide ions. The experimental data were analyzed by a Ferranti 1900 series computer. This procedure led to difficulties in some cases and graphical methods were then employed. The order of stability of the complexes was : Cl(NiII)< Br(NiII)∼Cl(PbII)< Br(PbII)< Cl(CdII)< Br(CdII). For each metal ion, the order of stability was : {F(MII)} Cl(MII)< Br(MII){CN(MII)} Structural changes, leading to long-lived species, may occur in the CoII-halide systems.

'The local charges show11 (in units of the electronic charge) are not the absolute charge densities, but represent the amount, Ap, by which the local charge density of pyridine is altered when the pyridinium ion is formed. In this process one unit positive charge is added to the pyridine nucleus resulting in a decrease in the local charge density, i.e. Ap is negative. Employing the simple relation, A6 = k A p , where A8 is the observed change in the proton shift (in p.p.m.), the constant k was found to have the value 9.5 p.p.m. per electron. For the present purpose the low-field displaceinent of the N-1-1 signal, resulting from the charge deficiency a t the N atom, was taken to be 336 cycles/sec. This is the difference in chemical shift between the N-1-1 group protons in the pyridinium ion and in pyrrole. The N-1-1 shift in the latter is -96 cycles/sec relative to CH2C12 which, if pyrrole were an aromatic system, must be corrected for the "ring current effect" (2). This correction is approxirnately -84 cycles/sec, giving a total shift of -180 cycles/sec. On combining this with the N-1-1 shift in the pyridiniuln ion, -516 cycles/sec, results in a net low-field displacement of 336 cycles/sec. The results, which are necessarily approximate, show that roughly 607' of the unit charge deficiency in the pyridiniunl ion is located a t the N atom, the remainder being distributecl on the carbon atoms in the ring as indicated. Finally the relative line width of the resonance spectra under the experimental conditions employed are of solne interest. In the spectrum of pyridine itself (Fig. l (a)) the signals of the a-protons are significantly broader than those of P ancl y protons. This broadening can be attributed to a shorter T I relaxation time of the a-protons caused by nuclear quadrupole relaxation effects of the N ' nucleus. Such effects are frequently encountered in nitrogen-containing compounds when a proton is directly bonded to the N atom, whereas in this instance the relaxation is evidently transmitted to protons two bonds removed. In the presence of trifluoracetic acid (Fig. 1 (b) , (c), and ( r l ) ) , the a-proton signals remain broad, and in addition the Pand y-protons are broaclenecl. 'I'his additional broaclening is no doubt due to proton exchange between the acid and the pyridiile nitrogen atom. The fact that the triplet structure of the N-1-1 proton is observable in the 5 mole% solution indicates that under these conditions the exchange rate lllust be considerably less than 400 times per second. With lower acid concentrations the proton exchange rate is much greater than this and the triplet N-I-I resonance cannot be observed.

MOST determinations of stability constants in alkali metal nitrate solvents have concerned the halide complexes of silver1. Recently the cryoscopic2, solubility3, polarographic4, galvanostatic5, spectroscopic6 and e.m.f.7 techniques have been used for investigating the formation of the halide complexes of various metals (for example, cadmium) in these solvents. A silver–silver bromide electrode has been used to study the bromo-complexes of cadmium and lead7. An attempt8 to use the silver–silver chloride electrode in a similar way to study chloro-complexes was not successful.

MEASUREMENTS of the differential capacitance of the electrical double-layer at an LiCl–KCl eutectic melt/platinum interface at 450° C have been made by Laitinen and Roe1 over a range of potentials from −0.34 V to −2.11 V versus a Pt/Pt2+ (1 M) reference electrode. Their curve of capacitance versus potential can be roughly divided into two regions: an anodic region of comparatively high specific capacitance (∼100 µF cm−2) and a cathodic region of low specific capacitance (∼50 µF cm−2), the transition between them occurring at approximately −0.8 V to −1.0 V. The high values of capacitance were attributed1,2 to the specific adsorption of chloride ions at potentials which are presumably anodic to the point of zero charge of this interface.

An arrangement is described which allows potential‐time measurements in galvanostatic pulse techniques to be performed 40–80 mμsec after initiation of the pulse.

The construction and performance is described of a glass electrode generally applicable to molten salt systems up to 550° C.