Citric acid is a weak acid that is found naturally in all citrus fruits. Unlike strong acids, weak acids ionize only partially when in solution. If you’ve ever sunk your teeth into a lemon or any other citrus fruit, you've tasted citric acid. But it's not just sour citrus fruits that have citric acid. All plants and animals have small traces of it. One reason is that it's an important intermediate in metabolism, which is the pathway that allows your body to get energy from carbs, fats, and proteins.

Citric acid doesn't have any color. It doesn't smell like anything either. If you put some on your tongue, you'd taste the acid. You might find it tastes pleasantly sweet and tart.

By itself, citric acid is a solid. If you put it into a solution, the pH will depend on its concentration. The pH of lemon juice is about 2 or 3. Many packaged food and nonfood items, such as cosmetics and cleaning products, contain manufactured citric acid, not the natural kind. Manufacturers add a man-made version of citric acid to processed foods. Medicines with citric acid in them are used to treat health issues such as kidney stones and blood clots.