Studies of analytical systems involving onium and basic dye cations and solvent extraction methods. The original intention of this project was to study selected onium extractions in continuation of previous work carried out in this laboratory. The extraction of Cr(VI) with onium salts into organic solvents had been studied by previous workers who had shown that Cr(VI) could just as readily be extracted from acid solution without the addition of an onium salt. A study has been made of the effect of various onium compounds, and different organic solvents on this extraction. The effect of pH, as well as interfering ions was studied. In the present study, in spite of the colour stability of the complex and the coefficient of variation being 0.4%, a low apparent molar absorptivity was obtained.