Sodium citrate

Sodium citrate is the sodium salt of citric acid with the chemical formula of Na₃C₆H₅O₇. Sodium citrate 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 chiefly used as a food additive, 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 lemon-lime and citrus soft drinks such as Ting, contributing to their tart tastes, and can also be found in such energy drinks as Rockstar and Red Bull.

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, disrupting the blood clotting mechanism.

As a conjugate base of a weak acid, citrate can perform as a buffering agent, 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.

Recently, Oopvik, et al. showed that use of sodium citrate (approx. 37 grams) improved running performance over 5 km by 30 seconds.

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 was used by chef Heston Blumenthal in his television series In Search of Perfection as a key ingredient in making cheese slices.