Choline chloride / tartaric acid room temperature ionic liquid was prepared and the obtained phase diagrams of the mixture showed eutectic point at 5 oc. The ionic liquid showed a conductive properties, high density and low PH values. Secondly, the dissolution of Co3O4, CrO3, NiO, CuO, and ZnO. Were studied and found soluble in choline chloride / tartaric acid ionic liquid as their solubilities were determined by measuring the dissolved metal by atomic absorption from room temperature up to 100 oc. The lattice energies of the metal oxides were deduced and the effects of the d- orbital electrons on the lattice energy were compared. In addition to their solubilities the above solution of metal oxides were investigates by ultraviolet visible spectroscopy. The spectra were measured and assigned to the expected coordination in the choline chloride/ tartaric acid ionic liquids, the effect of increasing temperature of the solution up to 100 oC were also studied and showed similar coordination but higher vibration with increasing temperature Racah factor for there complexes (B`) were determined together with field factor, crystal field splitting energy (Δo), nephelauxetic factors and molar absoptivities for each spectra at the variable temperatures.
