Neutralising value

Specific Gravity Solidifying Point Melting Point Neutralisation Value Mean Molecular Weight Iodine Value Refractive Index ... 

Based on soil depth, arable of 200 mm, pasture of 150 mm, neutralising value of 54% with 40%... 

The neutralising value is a measure of the calcium plus magnesium carbonate content of the limestone (expressed in terms of CaO — see glossary). 

Neutralising values of above 50% CaO are obtained with high purity limestones, but lower values can be offset by increasing the quantity added per unit area. 

In the UK, the Fertiliser Regulations [10.3] require the declaration of the neutralising value and, in the case of limestones other than chalks, the percentage passing a 150 pm sieve. 

The percentage CaCOs in the limestone should be at least 95 % — not only to provide the neutralising value to react with the oxides of sulfur, but also to mini-... 

Above pH 7, the production of bicarbonate reduces the effective neutralising value. Above pH 9, Mg(OH)2 precipitates, reducing the effective neutralising value. 

Most lime products currently used for liming have a top size of 6 mm or less. This suits modern mechanical spreading equipment and helps to ensure an even distribution. Because the neutralising values of lime products are often almost double those of agricultural limestone, the application rates are correspondingly lower. 

When selecting a product for agricultural liming, a critical factor is the delivered cost per unit of neutralising value [30.2]. In consequence, when lime is used, inexpensive grades of lime are favoured. TTiese include the fines screened from run-of-kiln lime, which contain more impurities (such as fuel ash, sulfur and clay) than the coarser fractions (see section 17.1.3). Hydrator rejects (section 20.4.3) and carbide lime (section 22.10) are also used. 

Some of the lime products complying with the UK s Fertiliser Regulations [30.3] are listed in Table 30.2. While they are characterised in terms of grading and MgO content, the only declaration required is the neutralising value. 

Neutralising value is an analytical term for that proportion of limestone, quicklime, or hydrated lime (expressed as CaO) that is capable of reacting with hydrochloric acid under specified conditions. It includes the contribution of CaCOs, CaO, Ca(OH)2, and the acid-soluble fraction of the calcium silicates, aluminates and ferrate. 

The supplier of lime must give a statement of the neutralising value (NV) of the liming material which is the same as the calcium oxide equivalent... 

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