Phase Behavior of Aqueous Na-K-Mg-Ca-CI-NO3 Mixtures: Isopiestic Measurements and Thermodynamic Modeling

A comprehensive model has been established for calculating thermodynamic properties of multicomponent aqueous systems containing the Na{sup +}, K{sup +}, Mg{sup 2+}, Ca{sup 2+}, Cl{sup -}, and NO{sub 3}{sup -} ions. The thermodynamic framework is based on a previously developed model for mixed-solvent electrolyte solutions. The framework has been designed to reproduce the properties of salt solutions at temperatures ranging from the freezing point to 300 C and concentrations ranging from infinite dilution to the fused salt limit. The model has been parameterized using a combination of an extensive literature database and new isopiestic measurements for thirteen salt mixtures at 140 C. The measurements have been performed using Oak Ridge National Laboratory's (ORNL) previously designed gravimetric isopiestic apparatus, which makes it possible to detect solid phase precipitation. Water activities are reported for mixtures with a fixed ratio of salts as a function of the total apparent salt mole fraction. The isopiestic measurements reported here simultaneously reflect two fundamental properties of the system, i.e., the activity of water as a function of solution concentration and the occurrence of solid-liquid transitions. The thermodynamic model accurately reproduces the new isopiestic data as well as literature data for binary, ternary and higher-order subsystems. Because of its high accuracy in calculating vapor-liquid and solid-liquid equilibria, the model is suitable for studying deliquescence behavior of multicomponent salt systems

INTENTIONAL COMMUNITIES IN RURAL SPACES

In this paper, we focus on intentional communities in the Western world. These communities consist of a variety of groups, with different characteristics, ideologies and motivations. Examples are eco-villages, religious communities and communities of lesbians. These groups intend, at least to some extent, to withdraw from mainstream urban society, challenging norms of urban life, e.g. wasteful behaviour, stressful lives or heterosexual stereotypes, and create their own places in rural areas. Key questions that we seek to address in the paper are: What types of intentional communities can be identified? To what extent are intentional communities withdrawn from the rural areas in which they are established? We attempt to answer these through discussing the results of a survey among 496 communities. Furthermore, we describe an example of the ecological type of community, since these communities are most explicitly challenging urban norms and values. Copyright (c) 2007 by the Royal Dutch Geographical Society KNAG.