Wikipedia:Today's second feature/March 5, 2006

Unripe lemon.

The lemon, Citrus × limon, is a citrus tree, a hybrid of cultivated origin. The fruit are cultivated primarily for their juice, though the pulp and rind (zest) are also used, primarily in cooking or mixing. Lemon juice is about 5% citric acid, which gives lemons a sour taste; its pH is 2.3, so because of its acidity, lemon juice is commonly used in chemistry experiments.

Photo credit: Jon Sullivan of PD Photo.org
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