A simple correlation has been observed between the extraction of strontium nitrate from nitric acid solution by cis-dicyclohexano-18-Crown-6 dissolved in a variety of oxygenated, aliphatic diluents and the molarity of water present in the organic phase. This correlation is attributed to the extraction of the hydrated nitrate ion and its solvation by the diluent, facilitated by the high concentration of dissolved water. Of the solvents studied, ketones yield the largest values of the extraction constant for a given water content, although C5and C6alcohols give the highest overall values.