ISO 20978:2020

This document specifies two methods for the determination of the neutralizing value (NV) of liming materials.
Method A is applicable to all liming materials except silicate liming materials.
NOTE 1    Examples of hard liming materials are limestone and dolomite. Examples of soft liming materials are chalk, marl and burnt lime.
Method B is applicable to all liming materials.
Neither method correctly takes into account the potential neutralizing value of material containing more than 3 % P2O5. For a more accurate agronomic assessment of products containing more than 3 % P2O5, EN 14984[8] is used to determine the liming efficiency.
NOTE 2  The methods described in ISO 6598 and ISO 7497 can be used for the determination of P2O5 content. Further information on P analyses is given in References [5] and [6].
NOTE 3  Carbonate consumes H+ and removes acidity in solution with subsequent dissociation to H2O and CO2. Forms of orthophosphate can consume H+ but are not dissociated to molecular forms that remove acidity. The acidity is back titrated with alkali causing an underestimation of NV.