This International Standard covers the chemical analysis of silicon carbide based abrasive grains and crudes. It is applicable for the determination of the surface impurities of abrasives grains and determining the SiC content of crushed crude when the silicon carbide content is greater than 95 % (m/m). When the grain size of the silicon carbide is greater than or equal to 15 μm, the determination of the loss on acid treatment is carried out according to the method given in 3.5 and the crudeSiC content (SíCR) according to the method given in 3.7. When the grain size of the silicon carbide is smaller than 15μm, the determination of the SiC content shall be carried out by the methods described in 4.3 and 4.4.2.1 or 4.4.2.3 and 4.5 because the methods given in 4.2 and 3.7 inevitably give false results due to oxidation. When the surface carbon content [w(Csurf)] is greater than 2 % (m/m), a coulometric determination according to the method described in 3.4.2.3 will give correct results. The gravimetric method described in 3.4.2.1 is only applicable to surface carbon contents which are greater than 2 % (m/m), if ignition is continued to a constant weight or a weight increase. The coulometric method described in 3.4.2.2 cannot be applied in cases where w(Csurf) is more than 2%.