Draft:Urea hydrochloride

Urea hydrochloride is the hydrochloride salt of urea. It is used in concrete etching and as a deep eutectic solvent. Its double salt with quinine hydrochloride has applications in surgical medicine.

Production
Urea hydrochloride and diurea hydrochloride may be formed by treating solid urea with hydrogen chloride or concentrated hydrochloric acid.

Properties
Urea hydrochloride is a deliquescent white solid, soluble in water and ethanol. It forms biuret and ammonium chloride upon heating to 130 C. Thermal decomposition also yields condensation products of isocyanic acid, such as cyanuric acid.

Uses
Urea hydrochloride has uses as a concrete cleaning and etching agent, as it removes water-insoluble metal salts in solution. In solution with betaine, urea hydrochloride has been investigated as a deep eutectic solvent for the dissolution of chitin.

The double salt of quinine hydrochloride and urea hydrochloride has been used since the early 20th century as a long-duration injectable local anesthetic for use in various surgeries. The solution was formulated in France in 1881 and was first recommended for use as a local anesthetic in 1907. While other quinine salts have the same anesthetic effect, quinine urea hydrochloride is preferred due to its exceptional solubility. Operations involving a quinine urea hydrochloride solution included surgeries on the tonsils, abdominal and rectal tissues. At the time, such operations were carried out using anesthetics that may have adverse side effects, such as cocaine. Quinine urea hydrochloride was also used in the treatment of sciatica and in 1931 was noted as one of the first treatments of anal fissures. It was still in use by at least 1971, at which point it was noted as one of the few widely adopted injection treatments for hemorrhoids.