Full Description

ISO 20978:2020 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.