methods of purifying 2 - methylthio - 5 - trifluoromethyl - 1 , 3 , 4 - thiadiazole include the steps of providing a first 2 - methylthio - 5 - trifluoromethyl - 1 , 3 , 4 - thiadiazole composition comprising 2 - methylthio - 5 - trifluoromethyl - 1 , 3 , 4 - thiadiazole and organic solvent ; performing a first extraction of the 2 - methylthio - 5 - trifluoromethyl - 1 , 3 , 4 - thiadiazole composition with a first inorganic acid solution ; and performing a second extraction of the 2 - methylthio - 5 - trifluoromethyl - 1 , 3 , 4 - thiadiazole composition with a second inorganic acid solution .