scope:

This part of ISO 21068 gives definitions and specifies techniques for the preparation of samples for the chemical analysis of silicon-carbide-containing raw materials and refractory products including: a) graphite brick containing silicon carbide;b) silicon carbide brick (includes the bricks containing silicon nitride); c) refractories containing carbon and/or silicon carbide mixed with clay; d) refractories containing carbon and/or silicon carbide mixed with silica (and fused silica); e) refractories containing carbon and/or silicon carbide mixed with high alumina material; f) refractories containing carbon and/or silicon carbide mixed with magnesia (and dolomite); g) refractories containing carbon and/or silicon carbide mixed with chrome mineral or magnesia-chrome materials; h) refractories containing carbon and/or silicon carbide except those described in a) to g) above. The items of chemical analysis described in ISO 21068, Parts 1 to 3 are as follows: 1) loss on drying (LOD); 2) loss on ignition (LOI); 3) total carbon, Ctotal; 4) free carbon, Cfree; 5) silicon carbide, SiC; 6) free silicon (Sifree); 7) free aluminium (Alfree); 8) free magnesium (Mgfree); 9) free iron (Fefree); 10) silicon(IV) oxide (SiO2).