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The extraction of gold(III) from hydrochloric acid solutions by means of the phosphine oxide Cyanex 925 was studied as a function of different variables: equilibration time, temperature, organic diluent, and concentration of gold, Cyanex 925, HCl, etc.; the system is selective with respect to the extraction of a number of metals. Gold(III) equilibrium loading isotherms were also obtained at 20°C. Experimental data were treated numerically showing that gold extraction can be explained assuming the formation of a complex with the general stoichiometry: HAuCl4L2, where L represents the extractant. For the extraction reaction log Kexto = 8.1. The stripping of gold from loaded organic phases can be achieved with water. Data on the extraction of HCl by Cyanex 925 are also presented.

The partition of gold(I) between aqueous cyanide solutions and organic phases of the mixture of the amine Primene JMT and the phosphine oxide Cyanex 923 in xylene was studied at various aqueous pH values, extractant mixtures and gold concentrations, different temperatures and equilibration times. The behaviour of the extraction system with different organic diluents, aqueous ionic strengths and the selectivity of the system with respect to the extraction of different metal-cyano complexes was also investigated. The gold(I) extraction mechanism is discussed on the basis of the experimental results and numerical treatment of the experimental data, the species formed in the organic phase having the probable stoichiometry HAu(CN)2RNH2(R3PO)n, n being 1 (log Kext 11.94 ± 0.07) or 2 (log Kext 12.45 ± 0.I5). Stripping of gold from loaded organic solutions was also studied using low ionic strength alkaline solutions (NaCN at 50°C or NaOH at 40°C).

The effectiveness of Cyanex 471X as extractant of gold(III) from hydrochloric acid solutions is demonstrated. The extraction system is endothermic and experimental variables, such as extractant concentration, organic diluent and hydrochloric acid concentration, influence it. Maximum gold extraction is obtained in the range of 1–3 M HCl concentrations. Equilibrium loading isotherms showed that the [Cyanex 47lX]/[Au (III)] molar relationship in the organic phase is near l.5, which is the probable stoichiometry of the extracted species defined by HAUCl4L (log Kext° = 3.79) and HAUCI4L2 (log Kext° = 6.34), L representing the organic extractant. The system seems to be suitable for the selective extraction of gold. Stripping of the metal can only be accomplished using sodium thiosulphate solutions, the corresponding reaction also being endothermic.

The extraction of gold(III) from hydrochloric acid solutions by the phosphine oxide Cyanex 923 was studied as a function of several variables, such as: equilibration time, temperature, organic phase diluent, metal and extractant concentrations and the presence of inorganic salts in the aqueous solutions. Gold(III) equilibrium loading and stripping isotherms were also obtained at 20°C and 70°C respectively. Experimental data were analyzed numerically using the computer program Image ). The results showed that the data can be explained assuming the formation of an HAuCl4L2 species in the organic phase, where L represents the organic extractant.

The application possibilities of gold(I) extraction from cyanide media by three primary amines, Primene 81R, Primene JMT and tridecylamine, has been studied taking in account several variables such as temperature, amine and initial metal concentrations, aqueous ionic strength and organic phase diluent; the selectivity of the extraction systems is also described. On the basis of graphical and numerical treatment an extraction mechanism for gold has been proposed

The extraction of gold(I) from cyanide solutions by tridecylamine/xylene solutions was studied at various temperatures, amine and metal concentrations. The influence of different diluents, aqueous ionic strength and the use of different mixtures of organophosphorous reagents and ketones with the amine in metal extraction was evaluated, and also the selectivity of the present extraction system. The gold-amine extraction mechanism is discussed.

En el artículo se aportan algunas ideas sobre la aplicación de las nuevas tecnologías de la información en la formación ocupacional a distancia a partir de los tres niveles generales de actuación de un sistema de formación ocupacional a distancia: nivel de producción, nivel de distribución y nivel de ejecución.

La vivienda de las comunidades in­dígenas Emberá-Catío que habitan actualmente en regiones tropicales húmedas del Departamento de An­tioquia constituye un elemento im­portante de identidad, que denota una conciencia de técnicas constructivas, materiales y significaciones manteni­das a través de generaciones por los Emberá.