Theory of solvent extraction of phosphoric and hydrochloric acids

Mixtures of hydrochloric and phosphoric acids were extracted from aqueous solution by organic solvents in a study to advance the theories of solvent extraction. Four solvents, t‐amyl alcohol, n‐butanol, cyclohexanol, and 2‐hydroxyethyl, n‐hexyl ether, were found to give high distribution coefficients of 0.1 to 0.5 for both acids. In studies using the ether type of solvent an increase of the pH of the aqueous phase from 0 to 10 reduced the distribution ratio of phosphoric acid by a factor of 1,100. The substitution of hydriodic acid for hydrochloric caused a 42% increase in the K of phosphoric acid, which could indicate the importance of internal pressure of the additive in extraction. Measurements of activity coefficients of the hydrochloric acid in aqueous solution showed only a 1% increase in its activity coefficient with addition of large amounts of phosphoric acid. This could not be sufficient to cause up to a 40% increase in the distribution coefficient of the hydrochloric acid with the addition of the phosphoric acid.