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The hydrates of cobalt and nickel nitrates are highly relevant as precursors for the preparation of mixed ceramics. In order to verify the numerous bibliographical data, systematic solubility measurements in aqueous medium under atmospheric pressure and a critical evaluation have been undertaken. By taking solvation phenomena into account, it has proved possible to correlate all the phenomena observed, to obtain equations representative of the liquidus curves, and to refine and extrapolate the experimental curves. The whole stable and metastable coordinates of the invariant transformations in both binary systems have been calculated or more accurately determined.

Les equilibres solide-liquide du systeme ternaire H 2 O - Al(NO 3 ) 3 - Zn(NO 3 ) 2 sont etudies par une methode synthetique basee sur la mesure de la conductivite. Six isothermes sont etablies et les phases trouvees sont: *a -25 et -15°C : glace, Zn(NO 3 ) 2 . 8H 2 O et Al(NO 3 ) 3 . 9H 2 O *a -5°C : glace, Zn(NO 3 ) 2 . 6H 2 O et Al(NO 3 ) 3 . 9H 2 O *a 10 et 25°C : Zn(NO 3 ) 2 . 6H 2 O et Al(NO 3 ) 3 . 9H 2 O *a 40°C : Zn(NO 3 ) 2 . 4H 2 O et Al(NO 3 ) 3 . 9H 2 O.

International audience; In many cases of miscibility gap in ternary systems, one critical point at least, stable or metastable, can be observed under isobaric and isothermal conditions. The experimental determination of this invariant point is difficult but its knowledge is essential. The authors propose a method for calculating the composition of the invariant solution starting from the composition of the liquid phases in equilibrium. The computing method is based on the barycentric properties of the conjugate solutions (binodal points) and an extension of the straight diameter method. A systematic study was carried out on a large number of ternary systems involving diverse constituents (230 sets ternary systems at various temperatures). Thus the results are presented and analyzed by means of consistency tests.

Anse / Asa Paulini - Contributions C. Coquide : - "Introduction" (avec J.-C. Beal, J.-P. Bravard, A. Lavocat, A. Schmitt, R. Tenu), p. 17-21 ; - Etablissement de La Citadelle" (et contributeurs), p. 141-183 ; - "Villa de Bancillon" (avec C. Ramponi, S. Nourissat et contributeurs), p. 184-255 ; - Lectures synthetiques sur le versant nord, rythmes et occupation du sol (et contributeurs), 256-266 ; - "L'enceinte romaine de Château Vieux a Anse..." (avec J.-C. Beal et contributeur), p. 266-284 ; -"Les Carrieres" (et contributeur), p. 286-289 ; -"Les Terres basses" : Bourdelan et Sauzey-Carra (avec J.-C. Beal, A. Lavocat), p. 341-347 ; -"Le dossier d'Asa Paulini : Relecture synthetique" (avec J.-C. Beal), p. 347-351.

The binary phase diagram NaBO2–H2O at ambient pressure, which defines the different phase equilibria that could be formed between borates, end-products of NaBH4 hydrolysis, has been reviewed. Five different solid borates phases have been identified: NaBO2·4H2O (Na[B(OH)4]·2H2O), NaBO2·2H2O (Na[B(OH)4]), NaBO2·2/3H2O (Na3[B3O4(OH)4]), NaBO2·1/3H2O (Na3[B3O5(OH)2]) and NaBO2 (Na3[B3O6]), and their thermal stabilities have been studied. The boundaries of the different Liquid + Solid equilibria for the temperature range from −10 to 80 °C have been determined, confirming literature data at low temperature (20–50 °C). Moreover the following eutectic transformation, Liq. → Ice + NaBO2·4H2O, occurring at −7 °C, has been determined by DSC. The Liquid–Vapour domain has been studied by ebullioscopy. The invariant transformation Liq. → Vap. + NaBO2·2/3H2O has been estimated at 131.6 °C. This knowledge is paramount in the field of hydrogen storage through NaBH4 hydrolysis, in which borate compounds were obtained as hydrolysis reaction products. As a consequence, the authors propose a comparison with previous NaBO2–H2O binary phase diagrams and its consequence related to hydrogen storage through NaBH4 hydrolysis.

It is very rare that a one-step process of extraction leads to the pure compound with a high degree of purity specified by an industrial application. The various stages of a synthesis process and possible secondary reactions may lead to the synthesis of more or less complex and highly diluted solutions. In this work, the rationale and strategy for extraction and purification of a high added value compound are discussed. All the thinking is based on the knowledge and the exploitation of phase diagrams and then developed for different unit operations of the process. The most significant research tools are the experimental data and the modelling of phase equilibrium to estimate the yield of each step of extraction. The significant example chosen involves all the basic methods of phase separation, starting with liquid-vapour equilibrium: stripping of high volatility components and then more or less complex distillation are classically employed. The theoretical plateau number can be deduced from the equilibrium equation curves. The second step is based on the study of the liquid-liquid equilibrium and is an intermediate step for enrichment of the solution when distillation is not possible. A final step based on solid-liquid equilibrium consists of the selective crystallization of the pure product at low temperature, in order to satisfy the requirements of purity and safety imposed by industrial use. The conclusion includes all isolation operations in the form of a general extraction and purification scheme.

International audience

Dans une publication anterieure, une equation semi-empirique du liquidus d'une phase solide stœchiometrique d'un systeme binaire a ete proposee. Dans ce travail, elle est appliquee au trace des diagrammes d'equilibre, a la determination des grandeurs thermodynamiques qui caracterisent la fusion et au calcul des coefficients d'activite des solutions saturees. L'enthalpie de fusion de la glace, calculee dans les differents systemes s'ecarte peu des determinations calorimetriques. Les ecarts semblent beaucoup plus importants dans le cas des hydrates. D'une maniere generale, la concordance entre les valeurs des temperatures et des compositions, issues de la mesure et du calcul, est excellente.

Une equation du liquidus d'une phase terminale ou intermediaire est proposee. Applicable a tout le domaine de temperature et de composition, elle constitue une expression analytique representative du liquidus d’une phase solide quelconque des systemes H2 O-MCl2 ou M = Mg, Ca, Sr ou Ba.Dans le cadre de ce travail, nous avons montre qu'elle permet la selection et l'affinement des mesures de solubilite provenant de determinations experimentales diverses. Elle autorise une large extrapolation des courbes de liquidus en temperature et composition. Enfin, elle permet de confirmer ou de modifier l'attribution d'une mesure a un equilibre determine.

Lavagne Henri, Tenu Richard. La Grange-du-Bief à Anse (Rhône) : nouvelles recherches et mosaïques inédites. In: Gallia, tome 43, fascicule 1, 1985. pp. 147-166.

Since the solid-liquid equilibria of water-salt systems can be determined by conductimetry, a conductimeter has been built and perfected. By means of a synthetic method, the conductimeter enables fast, comprehensive and accurate determination of isothermal sections of a multi-component system: solubility, solid phase composition, etc. The method and apparatus have been applied to the study of the quaternary system H 2 O-NaCl-CaCl 2 -SrCl 2 . The space diagram of the isotherm at 65°C has been established by the study of two isoplethic sections. Three solid phases are observed at this temperature: the anhydrous sodium chloride and the dihydrates of calcium and strontium chlorides.