This European standard specifies methods to determine the potential of sulfide bearing materials for the formation of acidic drainage. Specified are methods for determining both the acid potential (AP) and the neutralisation potential (NP) of the material. From these results the net neutralisation potential (NNP) and the neutralisation potential ratio (NPR) are calculated. This European standard is applicable to all sulfide bearing wastes from the extractive industries excluding wastes which will have pH lt; 2 in the initial step of the procedure described in 8.2.3.