Sodium citrate refers to any of the sodium salts of citric acid namely monosodium citrate, disodium citrate and trisodium citrate.

As food additives, the 3 forms of the salt are also collectively known by the E number E331 and the term sour salt is coined for this chemical, because it possesses flavours of sour and salty.

Sodium citrate is sometimes used as an acidity regulator in drinks, and also as an emulsifier for oils when making cheese. It allows the cheeses to melt without becoming greasy. Sodium citrate can be used as a flavouring or as a food additive.

The term sodium citrate is most commonly used to refer to trisodium citrate. However, it can also refer to other sodium salts from citrate — such as disodium citrate and monosodium citrate. It is also known by its IUPAC name as trisodium 2-hydroxypropane-1,2,3-tricarboxylate, and it has the chemical formula Na3C6H5O7 and the assigned CAS Number 68-04-2. Other names for sodium citrate include citric acid, trisodium salt, and 1,2,3-propanetricarboxylic acid.

Food grade sodium citrate — identified by the E number E331 — has many commercial applications. One of its primary uses is to prolong the shelf life of food products. In addition to its widespread use as a preservative, its flavoring characteristic makes it a popular ingredient in many beverages — especially those with citrus flavors.

Though few people are aware of sodium citrate’s formal name, they rely on its strength as an alkalizer when they use Alka Seltzer tablets — making it quite a popular compound found in many households.