Sodium citrate

Sodium citrate is the sodium salt of citric acid. 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. Sodium citrate gives club soda both its sour and salty flavors.