Trisodium citrate has the chemical formula of Na₃C₆H₅O₇.It is some times referred to simply as sodium citrate, though sodium citrate can refer to any of the three sodium salts of citric acid. It possesses a saline, mildly tart flavor. For this reason, citrates of certain alkaline and alkaline earth metals (e.g. sodium and calcium citrates) are commonly known as "sour salt" (occasionally citric acid is erroneously termed sour salt).
Sodium Citrate is a buffer and sequestrant obtained from citric acid as sodium citrate anhydrous and as sodium citrate dihydrate or sodium citrate hydrous. the crystalline products are prepared by direct crystallization from aqueous solutions. sodium citrate anhy- drous has a solubility in water of 57 g in 100 ml at 25°c, while sodium citrate dihydrate has a solubility of 65 g in 100 ml at 25°c. it is used as a buffer in carbonated beverages and to control ph in preserves. it improves the whipping properties in cream and pre- vents feathering of cream and nondairy coffee whiteners. it pro- vides emulsification and solubilizes protein in processed cheese. it prevents precipitation of solids during storage in evaporated milk. in dry soups, it improves rehydration which reduces the cooking time. it functions as a sequestrant in puddings. it functions as a complexing agent for iron, calcium, magnesium, and aluminum. typical usage levels range from 0.10 to 0.25%. it is also termed trisodium citrate.
2 - 1 - Food
Sodium citrate is chiefly used as a food additive E331, usually for flavor or as a preservative. Sodium citrate is employed as a flavoring agent in certain varieties of club soda. Sodium citrate is common as an ingredient in Bratwurst, and is also used in commercial ready to drink beverages and drink mixes, contributing a tart flavour.
2 - 2 - Buffer
As a conjugate base of a weak acid, citrate can perform as a buffering agent or acidity regulator, resisting changes in pH. Sodium citrate is used to control acidity in some substances, such as gelatin desserts. It can be found in the mini milk containers used with coffee machines. The compound is the product of antacids, such as Alka- Seltzer, when they are dissolved in water.
2 - 3 - Medical uses
In 1914, the Belgian doctor Albert Hustin and the Argentine physician and researcher Luis Agote successfully used sodium citrate as an anticoagulant in blood transfusions. It continues to be used today in blood collection tubes and for the preservation of blood in blood banks. The citrate ion chelates calcium ions in the blood by forming calcium citrate complexes, disrupting the blood clotting mechanism.
Sodium citrate is used to relieve discomfort in urinary tract infections, such as cystitis, to reduce the acidosis seen in distal renal tubular acidosis, and can also be used as an osmotic laxative. It is a major component of the WHO Oral Rehydration Solution.