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  • 1
    ISSN: 1573-0867
    Keywords: Chemical extractants ; solubility percentages ; impurity effects ; phosphate rock
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The influences of calcium chloride, calcium sulphate, monocalcium phosphate, monosodium phosphate, calcium carbonate, sodium carbonate and iron and aluminium sulphates on the solubilities of two phosphate rocks (both ground and unground) in 2% citric and 2% formic acids have been examined. All of these potential ‘impurity’ elements can affect the solubility of the phosphate rock through a variety of mechanisms, including common ion effects, complexation, acid-base reactions and reduction. 2% formic acid solubilities were slightly more influenced by these effects than 2% citric acid figures, militating against the use of this extractant for assessing mixed component products at present being manufactured in New Zealand. Solid to solvent and P to solvent ratios were also found to affect the solubilities of raw phosphate rocks and a correction for the differences in total P content of the phosphate rocks to produce a consistent P to solvent ratio in solubility tests is suggested. This study has indicated that alternative methods for assessing phosphate rocks in admixture with other components should be examined in future.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Nutrient cycling in agroecosystems 31 (1992), S. 137-149 
    ISSN: 1573-0867
    Keywords: Extraction techniques ; partially acidulated phosphate rocks ; phosphate rock solubilities ; water solubilities ; neutral ammonium citrate solubilities ; 2% citric acid solubilities ; 2% formic acid solubilities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Alternative extraction techniques for assessing the ‘available P’ content in multi-component fertilisers such as partially acidulated phosphate rocks have been examined. Two types of double extraction method have been investigated, one involving sequential extraction procedures, and a second examining both the initial fertiliser and its residue independently, using either water or cold neutral ammonium citrate as the first extractant, and either 2% citric or 2% formic acid as the second solvent. The latter method, which used cold neutral ammonium citrate as the initial extractant, produced the most consistent results and provided a reproducible assessment of the solubility of the phosphate rock residue; it was not obvious which second solvent was preferable. Comparisons between the original phosphate rocks and their extracted residues indicated that there were many subtle influences which affected the solubility of the phosphate rock components, but a general ‘deactivation’ of phosphate rock residues on acidulation as previously suggested was not apparent. Before any particular method can be recommended as an alternative to existing one step extraction techniques it is necessary to confirm its validity through agronomic trials.
    Type of Medium: Electronic Resource
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