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) SiC raw materials; b) graphite brick containing silicon carbide; c) silicon carbide brick (includes the bricks containing silicon nitride, silicon oxynitride, sialon); d) refractories containing carbon and/or silicon carbide mixed with clay; e) refractories containing carbon and/or silicon carbide mixed with silica (and fused silica); f) refractories containing carbon and/or silicon carbide mixed with high alumina material; g) refractories containing carbon and/or silicon carbide mixed with magnesia (and dolomite); h) refractories containing carbon and/or silicon carbide mixed with chrome mineral or magnesiachrome materials; i) 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) dioxide (SiO2); 11) aluminium oxide (Al2O3); 12) iron(III) oxide (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.). ISO 21068-4 describes XRD methods for the determination of mineralogical phases typically apparent in nitride and oxy-nitride bonded silicon carbide refractory products.