Trisodium citrate has the chemical formula of Na3C6H5O7. It is sometimes 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 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 and Chinotto, contributing to their tart tastes, and can also be found in such energy drinks as Rockstar and Red Bull.
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.
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.
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 is used as an antacid, especially prior to anaesthesia for caesarian section to reduce the risks associated with the aspiration of gastric contents.