In chemistry, a hydrochloride is an acid salt resulting, or regarded as resulting, from the reaction of hydrochloric acid with an organic base (e.g. an amine). An alternative, more elegant name is chlorhydrate, which comes from French. An archaic alternative name is muriate, derived from hydrochloric acid's ancient name: muriatic acid.
For example, reacting pyridine (C5H5N) with hydrochloric acid (HCl) yields its hydrochloride salt, pyridinium chloride. The molecular formula is either written as C5H5N·HCl or as C5H5NH+ Cl−.
Converting insoluble amines into hydrochlorides is a common way to make them water-soluble. This characteristic is particularly desirable for substances used in medications. The European Pharmacopoeia lists more than 200 hydrochlorides as active ingredients in medications. These hydrochlorides, compared to free bases, may more readily dissolve in the gastrointestinal tract and be able to be absorbed into the bloodstream more quickly. In addition, many hydrochlorides of amines have a longer shelf-life than their respective free bases.