Homogenization of Water/Chloroform and Water/n‐Butanol Mixtures with Tetraalkylammonium Halides. Phase Diagrams and Properties of the Homogeneous Phases

Abstract

AbstractWe report on two ternary systems with a ternary miscibility gap. They consist of two immiscible solvents (water and chloroform or water and n‐butanol) and salts which can close the miscibility gap. These salts are unsymmetrical tetraalkylammoniumhalides R3R'N+X− (X− = Cl−, Br−, I−). We determined the binodal curves in the ternary phase diagrams. In the homogeneous region, we measured densities, kinematic viscosities, and electrical conductivities. At constant mole fractions of salt, the viscosities increase and reach constant values while the conductivities decrease monotonously with increasing mole fractions of the organic solvent. Addition of salt to a given mixture of the solvents leads to a monotonous increase of the viscosities while the conductivities first increase, then go through maxima and decrease again. By X‐ray analysis we determined the crystal structure of methyl‐tri‐n‐propylammonium iodide. The lattice is triclinic, space group P1. A ternary compound, containing the salt together with chloroform and water could also be prepared. The crystal is disordered at room temperature, a skeleton of tetraalkylammonium ions is present which contains channels. In these channels, chloroform and water molecules seem to be mobile. The X‐ray analysis shows no special positions for these solvent molecules. The structure of this compound does not indicate heteroselective solvation. This concept therefore should not be used in the discussion of the homogenization by these salts.