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);
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.).