Steve Perry, age 16, of Akron, Ohio, for his question:

WHO DISCOVERED CITRIC ACID?

Citric acid is a common organic acid that gives lemons, oranges and other citrus fruits their sour tastes. A Swedish chemist named Carl Wilhelm Scheele was the first person to isolate citric acid from lemon juice. Scheele made his discovery back in 1784.

Lemon juice contains six to seven percent citric acid.

The name citric comes from the Latin word citrus, which means citron tree, a close relative to the lemon and lime trees.

Citric acid is used as a flavoring for soft drinks and medicines. Industry uses it in chemicals, alkyd resins and as a mordant or 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. It combines with metals to form salts called citrates.