ISO 20978-2020 pdf free.Liming material — Determinationof neutralizing value — Titrimetricmethods.
1.Scope:This document specifies two methods for the determination of the neutralizing value (NV) of limingmaterials.Method A is applicable to all liming materials except silicate liming materials.NOTE1 Examples of hard liming materials are limestone and dolomite.Examples of soft liming materials arechalk, marl and burnt lime.Method B is applicable to all liming materials.Neither method correctly takes into account the potential neutralizing value of material containingmore than 3 % P-0z.For a more accurate agronomic assessment of products containing more than 3 %P2O5,EN 14984lis used to determine the liming efficiency.NOTE2 The methods described in 1So 6598 and ISo 7497 can be used for the determination of P.,0 content.Further information on P analyses is given in References [5] and [6].NOTE3 Carbonate consumes H* and removes acidity in solution with subsequent dissociation to H,0 and CO.Forms of orthophosphate can consume H* but are not dissociated to molecular forms that remove acidity.Theacidity is back titrated with alkali causing an underestimation of NV.
2.Normative references:The following documents are referred to in the text in such a way that some or all of their contentconstitutes requirements of this document. For dated references, only the edition cited applies.Forundated references, the latest edition of the referenced document (including any amendments) applies.ISo 3310-1,Test sieves —Technical requirements and testing —Part 1:Test sieves of metal wire clothIS0 3696, Water for analytical laboratory use —Specification and test methods
ISO 8157, Fertilizers and soil conditioners —Vocabulary
ISO 14820-2,，Fertilizers and liming materials — Sampling and sample preparation — Part 2: Samplepreparation
3.Terms and definitions:For the purposes of this document, the terms and definitions given in ISO 8157 apply.
4.Principle:Dissolution of the sample in a specified quantity of hydrochloric acid standard solution.Determinationof the excess acid by back titration with a sodium hydroxide standard solution.This solution can be purchased from a chemical supply company certified to have a concentrationwithin a 0,4 % variance (0,498 M to 0,502 M).lf preparing from concentrated HCl, determine the exact concentration of the solution by titration withsodium hydroxide standard solution (5.3) using phenolphthalein solution (5.4) as indicator.Apply the appropriate correction factor in the calculation of the results (see Clause 9).ln case of any doubt about the concentration of the HCl solution, measuring the neutralizing value of aprecipitated calcium carbonate (PCC,5.6) is recommended.ISO 20978 pdf download.