is a crystallline, clear powder or crystal, that occurs in all metabolic organisms (up to 1 kg in a human body daily). It belongs to the fruit acids and is the most widespread acid in the plant kingdom. The citric acid was 1784 for the first time proved in lemon juice. The suspicion is that is was alreday known under a different name. The discovery is estimated around the 9th century. The acid was originally obtained from lemon fruits, but nowadays it is produced industrial by fermentation of molasses or corn. Citric acid is available as anhydrate or monohydrate. Salts and esters are known as citrates.