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); 11) aluminium oxide (Al2O3); 12) iron(III) oxide (total iron oxide calculated as Fe2O3); 13) titanium(IV) oxide (TiO2); 14) calcium oxide (CaO); 15) magnesium oxide (MgO); 16) sodium oxide (Na2O); 17) potassium oxide (K2O); 18) chromium(III) oxide (Cr2O3); 19) zirconium oxide (ZrO2); 20) boron oxide (total boron calculated as B2O3); 21) nitrogen; 22) oxygen; 23) nitrides (undifferentiated: Si3N4, AlN, BN, sialon, oxy-nitrides, etc.).