This method is the best available at the present time. It was primarily intended for samples containing 40 % (m/m) or more but has been extended to lower ranges. The principle is based on dehydration of a quantity of the test sample. Formation of a complex between o-cresol and cineole (having a crystallizing point not lower than 1, 2 ?C) by addition of excess cineole to a test portion of the dehydrated sample. Determination of the crystallizing point of the complex in a crystallizing point apparatus. Calculation of the content from the water content of the test sample and the crystallizing point of the complex. The relation between crystallizing point and o-cresol content of o-cresol/cineole mixtures is given in a table. ISO 1897/8 replaces ISO Recommendation R 1910-1971.