Citric Acid

About This Product

Citric acid, a tribasic hydroxy acid with formula C6H8O7 and CAS number 77-92-9, is produced by fermenting sugar with Aspergillus niger and supplied as anhydrous or monohydrate crystals. In industrial use its value lies in chelation rather than acidity. Three carboxyl groups and a hydroxyl arranged on a short carbon chain allow the molecule to wrap around a metal ion and hold it in a soluble complex, and that is what drives its main applications. In clean-in-place systems it dissolves the calcium and magnesium scale that builds in heat exchangers and pasteurisers, and does so without chloride, so it is safe on stainless steel where hydrochloric acid is not. In metal finishing it is the reagent for citric acid passivation of stainless steel, which strips free iron from the surface and allows the protective chromium oxide layer to re-form, increasingly replacing nitric acid passivation on safety and effluent grounds. In cleaning formulations it sequesters hardness ions so surfactant is not wasted, providing a readily biodegradable substitute for phosphate builders. It is used in CIP and descaling systems, stainless steel passivation, metal cleaning, detergent building, boiler cleaning and concrete admixtures. Bio Green Chem supplies anhydrous and monohydrate citric acid to specification on assay, water, oxalate, sulfate, chloride and heavy metals.