This International Standard specifies three methods for the determination of the hexamethylenetetramine (“hexa”) content of phenolic resins. The three methods are equivalent. The Kjeldahl method described in Clause 3 is not applicable if there are other components containing nitrogen in the phenolic resin. The perchloric acid method and the hydrochloric acid method described in Clause 4 and Clause 5, respectively, are only applicable if there are no other basic or acidic additives in the resin. If the resin contains additives which can be oxidized by perchloric acid, only the hydrochloric acid method (Clause 5) is applicable.