Citric, << SIHT rihk, >> acid is a common organic acid that gives lemons, oranges, and other citrus fruits their sour taste. Lemon juice contains 5 to 8 percent of the acid. The name citric comes from the Latin word citrus, which means citron tree (similar to lemon and lime trees). Carl Wilhelm Scheele, a Swedish chemist, first isolated citric acid from lemon juice in 1784.
Citric acid is used as a flavoring for soft drinks and pharmaceuticals. Industry uses it in chemicals, alkyd resins, plasticizers, inks, and as a mordant (dye-fixative). It is also used to clean and polish steel, and to preserve color and flavor in canned and frozen fruits and fish. Citric acid is prepared commercially from fermentation of sugar, and by extraction from lemon juice, lime juice, and pineapple canning residues.
Pure citric acid forms colorless, odorless crystals that have a pleasant, sour taste. It is very soluble in water and it melts at 153 °C. Citric acid combines with metals to form salts called citrates.
