Phase separation alkali effect

Phase diagrams, at 25° C, were determined for potassium acetate-water-dioxane, potassium acetate-water-tetrahydro-furan, and potassium chloride-water-tetrahydrofuran. Potassium acetate exceeded potassium chloride in its capacity to stratify aqueous solutions of either dioxane or tetrahydro-furan. Kobsevs (1) investigations revealed that the greater the solubility of an alkali metal salt, the greater its salting-out effect. The relative order of the water solubilities of the salts studied are potassium acetate > > potassium chloride. More potassium acetate is required to cause stratification in aqueous dioxane than is necessary to obtain the same results in aqueous tetrahydrofuran. It is proposed that, in comparison to dioxane, tetrahydrofuran forms a weaker association with water and, hence, the cations can more easily break these bonds causing liquid-phase separation. 

This section discusses the effect of alcohol on AS compatibility, and the effects of alkali, surfactant, and polymer in ASP systems. Factors affecting phase separation, IFT, and wettability are discussed as well. 

Some interesting effects associated to the presence of well-defined structural units appear on a broad class of binary alloys formed by mixing an alkali metal (Li, Na, K, Rb, Cs) with a tetravalent metal like Sn or Pb. Due to the large difference in electronegativities it is normally assumed that one electron is transferred from the alkali to the tetravalent atom. As the Sn- or Pb-anions are isoelectronic with the P and As atoms, which in the gas phase form tetrahedral molecules P4 and AS4, in the same way the anions group in the crystal compounds forming (Sn4)4- and (Pb4)4- tetrahedra, separated by the alkali cations. This building principle was developed by Zintl in the early thirties [1], and the presence of such tetrahedra has been detected in the equiatomic solid compounds of Pb and Sn with Na, K, Rb and Cs, but not with Li [2, 3, 4]. In this paper we focus on alkali-lead alloys. 

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