This method is use with sludge, paste-like or solid matter. If the sludge sample is sufficiently fluid, direct measurement should be made. If the sludge sample contains relatively little water the measurement must be carried out after dilution with water.
DIN EN 12176:1998 history
1998DIN EN 12176:1998 Characterization of sludge - Determination of pH-value; German version EN 12176:1998