In chemistry,<unk>  generally refers to any<unk>  that can lose proton(s) in an<unk> –base reaction. The term is used slightly differently in other fields. For example, in renal physiology,<unk>  is a term to describe<unk> s such as phosphoric<unk> , sulfuric<unk>  which are involved in renal physiology. It is used to explicitly exclude ammonium (NH4+) as a source of<unk> , and is part of the calculation for net<unk>  excretion. It gets its name from the use of NaOH in<unk> –base titration to estimate the quantity of<unk> .
Titratable acid
Glycoside
Azo compound
Iminosugar
Protelean
Lime 
Keratolytic
Protein 