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An Acid‐Free Vanadate‐Molybdate Reagent for the Determination of Total Phosphorus in Soils
Author(s) -
Tandon H. L. S.,
Cescas M. P.,
Tyner E. H.
Publication year - 1968
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1968.03615995003200010012x
Subject(s) - reagent , molybdate , chemistry , soil water , vanadate , chromate conversion coating , chromium , inorganic chemistry , chloride , ammonium molybdate , molybdenum blue , phosphorus , zinc , organic chemistry , environmental science , soil science
An acid‐free vanadate‐molybdate reagent was developed for the spectrophotometric determination of P in HClO 4 digests of soils. The optimum acidity in the analysis is derived from the residual acidity of the HClO 4 digest of soils. A comparative study of the proposed reagent with a commonly used molybdenum‐blue method on ten widely different soils indicated that the proposed method gave highly reproducible results and was not affected by high amounts of Fe 3+ which is invariably present in soils. In rare cases chromium interference can be serious because of the similarity of the color of the chromate ion to that of the molybdivanadophosphoric complex. For soils low in chromium, chromate interference can be removed by volatilization as chromyl chloride during the digestion. The modified reagent greatly simplifies the determination of total P and is admirably suited for automated analysis.