Mixture of tartaric acid, malic acid and acetanilid crystals, polarised light micrograph. Tartaric acid is an organic acid that occurs naturally in many fruits, most notably in grapes, but also in bananas and citrus fruits. Malic acid is found in certain fruits and wines. It's used in foods and cosmetics, and sometimes as medicine. Acetanilide is a synthetic organic compound which has analgesic and fever-reducing properties. Magnification: x93 when printed 10 centimetres wide.