Sodium citrate
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Sodium citrate is the sodium salt of citric acid with the chemical formula of Na3C6H5O7. It is chiefly used as a food additive, usually for flavor or as a preservative. In this sense, it is similar to calcium citrate.
Like citric acid, sodium citrate has a sour taste. Like other salts, however, it also has a salty taste. For this reason, citrates such as sodium and calcium citrate are common known as sour salt(sometimes, people refer to citric acid as sour salt). Sodium citrate gives club soda both its sour and salty flavors. Sodium citrate is common in lemon-lime soft drinks, and it is partly what causes them to have their sour taste.
In 1914, the Belgian doctor Albert Hustin successfully used sodium citrate as an anticoagulant in blood transfusions for wounded soldiers. 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.