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Pure Appl. Chem., 2000, Vol. 72, No. 12, pp. 2275-2287

Influence of chloride, water, and organic solvents on the physical properties of ionic liquids

Kenneth R. Seddon*, Annegret Stark and María-José Torres

QUILL Centre, The Queen's University of Belfast, Stranmillis Rd., Belfast BT9 5AG, Northern Ireland, UK

Abstract: We report here the first systematic study of the effect of impurities and additives (e.g., water, chloride, and cosolvents) on the physical properties of room-temperature ionic liquids. Remarkably, it was discovered that the viscosity of mixtures was dependent mainly on the mole fraction of added molecular solvents and only to a lesser extent upon their identity, allowing viscosity changes during the course of a reaction to be entirely predictable. While the addition of such molecular solvents decreases the viscosity and density, chloride impurities, arising from the preparation of the ionic liquids, increase viscosity dramatically. The commonly used methods of preparation were validated with respect to chloride impurity.