1.1 This International Standard specifies three methods for the determination of free sulfur in vulcanized rubber: two versions of the copper spiral method, and the sodium sulfite method. 1.2 The copper spiral methods are also applicable, subject to the limitations described in clause 4, to unvulcanized compounds. 1.3 Annex A gives a table listing the sulfur contribution, as a percentage by mass, to these free-sulfur methods for various commercial accelerators.