(for acetoacetic acid in the urine) filter, in order to remove the phosphates, and add a few drops of a solution of ferric chloride, which produces a deep red color, which disappears when sulfuric acid is added. (for bile pigments in the urine) shake urine with an equal measure of chloroform and then add iodine tincture and potassium hydroxide to the separated chloroform; a yellow or yellowish brown color is produced (Charles Frédéric Gerhardt).