This part of ISO 6528 specifies an oxygen combustion flask method for the determination of the total sulfur content of rubber. The method is applicable for the determination of all the sulfur present in a rubber or rubber product, except that contained in barium sulfate. It is applicable to NR, CR, SBR, BR, IR, IIR, EPDM, NBR and ebonite. (The meanings of these designations are given in ISO 1629:1987, Rubber and latices — Nomenclature.) This method gives unreliable (usually low) results in the presence of lead, antimony, zinc, barium and calcium compounds. If calcium carbonate is the only calcium compound present, good results can be obtained by modifying the absorbing solution.