  
Citric acid is a colourless, odourless organic compound with the formula C6H8O7, or specifically HOC(CO2H)(CH2CO2H)2. It occurs naturally in citrus fruits; oranges, tomatoes and lemons contain the highest amount of citric acid. Citric acid makes up about 5–8% of a lemon's juice. The pH of pure citric acid is typically around 2-3 depending on the concentration, as it is considered a weak acid.
Citric acid plays a role in the metabolism of all oxygen-using organisms. It is one of a series of compounds involved in the physiological oxidation of fats, proteins and carbohydrates to carbon dioxide and water. More than two million tons of citric acid are manufactured every year. It is used widely as an acidifier, for flavouring, as a preservative, and as a chelating agent. In soft drinks and candy, citric acid is used due to its sourness. It is also used in the manufacturing of soap and detergent, as well as for electroplating and leather tanning. Citric acid is useful in cosmetics to remove dead skin. It also diminishes wrinkles and improves skin tone. |