Sodium Citrate

About This Product

Sodium citrate is supplied chiefly as trisodium citrate, C6H5Na3O7 with CAS number 68-04-2, as white crystals or granules, freely soluble in water and giving a mildly alkaline solution. It does the same chelating job as citric acid but without the acidity, and that distinction determines when each is specified. Free citric acid dissolves scale aggressively but attacks soft metals, etches concrete and cannot be used on alkaline-sensitive systems. The sodium salt binds calcium, magnesium, iron and copper just as effectively while leaving pH near neutral or slightly alkaline, so it can be used where the substrate would not tolerate acid. In electroplating it holds metal ions in solution as citrate complexes, which controls deposition rate and improves throwing power in the bath. In cleaning formulations it sequesters hardness so surfactants are not consumed forming scum, and it is readily biodegradable, which is why it substitutes for phosphate builders under eutrophication rules. In medicine the same calcium binding makes it an anticoagulant for blood collection. It is used in electroplating baths, detergents and cleaners as a builder, boiler and cooling water treatment, textile processing and as a buffer. Bio Green Chem supplies sodium citrate to specification on assay, pH, loss on drying, oxalate, chloride, sulfate and heavy metals.