A process and apparatus for the regeneration of contaminated acid. The process involves cooling the contaminated acid to a lower temperature sufficient to form at least one liquid hydrate of the acid without forming a solid hydrate of the acid, maintaining the contaminated acid at the lower temperature for a time sufficient to form at least one liquid hydrate of the acid and precipitate an amount of the contaminants, separating the precipitated contaminants from the cooled acid, and warming the acid to decompose the liquid hydrate.