ISO 9028:2006 specifies methods for disintegration of raw rubber and rubber products by nitric acid or by a mixture of nitric and sulfuric acids. This International Standard is generally applicable, but is essential where potentially volatile elements or combinations of elements are present (i.e. As, Sb, Bi, and Zn + Cl, Cu + Cl and Pb + Cl). It is useful in these cases because lower temperatures are involved which result in less loss by volatilization.
These methods will be used in order to produce solutions for the determination of metals, for example as traces, if the application of ISO 247, Rubber - Determination of ash, is not advisable. These methods prevent loss of volatile metal derivatives and the formation of insoluble metal silicates (which may result during dry ashing of halogenated rubbers containing zinc or of rubbers filled with silica).