On boiling with water, they are partially reconverted into the hydroxy acids.
But along with these three general classes are found all kinds of connecting links: Acid salts, basic salts, hydroxy acids, etc.
Having, adding, or substituting a hydroxyl radical in a compound: hydroxyapatite.
hydroxyl hy·drox·yl (hī-drŏk'sĭl)
The univalent radical or group OH, a characteristic component of bases, certain acids, phenols, alcohols, carboxylic and sulfonic acids, and amphoteric compounds.