Lactic acid is an acid that is very common in nature. Lactic Acid is a carboxylic acid with a chemical formula of C3H6O3. Carl Wilhelm Scheele discovered it in milk that had gone sour, in 1780. Today it is used as an additive to food, to produce a sour taste. Contrary to popular belief, it is not produced in muscles when a person exercises. Lactate, on the other hand, is created within the muscles the more you exercise.