ISO 6598:1985 PDF

Fertilizers — Determination of phosphorus content — Quinoline phosphomolybdate gravimetric method

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Title (English):

ISO 6598:1985

Fertilizers — Determination of phosphorus content — Quinoline phosphomolybdate gravimetric method

Document status:: Active
Format:: Electronic (PDF)
Number of pages:: 3
Publication date:: September 19, 1985
Edition:: ISO IS 6598 edition 1 version 1
ICS:: 65.080

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Description (English):

The method consists in precipitating, after hydrolysis if necessary, of orthophosphate ions in the form of quinoline phosphomolybdate, in an acid medium and in the presence of acetone, at approximately 75 °C, followed by filtrating, washing drying and weighing of the precipitate obtained.

Technical details

Technical committee: ISO/TC 134 - Fertilizers, soil conditioners and beneficial substances
SKU: ISO 6598:1985

Abstract

Overview

ISO 6598:1985 specifies a gravimetric method for determining phosphorus content in fertilizers by precipitating orthophosphate as quinoline phosphomolybdate. The procedure - applicable to natural phosphate materials and manufactured fertilizers - includes hydrolysis if non‑orthophosphate forms are present, precipitation in an acidic/acetone medium at about 75 °C, followed by filtration, washing, drying and weighing of the precipitate. Results are reported as percentage of P2O5 (pentoxide of diphosphorus).

Key topics and technical requirements

Principle: Convert orthophosphate to a quinoline phosphomolybdate precipitate; quantify phosphorus gravimetrically.
Hydrolysis: Required when phosphate species other than orthophosphate are present; typically reflux about 1 hour.
Reagents: Analytical‑grade reagents only. The standard specifies prepared solutions (A–E) including molybdate, citric acid, nitric acid and quinoline; acetone is used as solvent.
Apparatus: Common lab equipment plus:
- 500 ml wide‑neck conical flask
- Fritted glass crucible (porosity P10 or P16)
- Oven (250 ± 5 °C), desiccator, and a heating device without an open flame
Procedure highlights:
- Add precipitant solution and heat to near‑boiling (~75–80 °C) rapidly.
- Cool, allow precipitate to settle, decant and filter under vacuum.
- Wash repeatedly, transfer to crucible, dry to constant mass at 250 °C and weigh to 0.0001 g precision.
- Add acetone to filtrate and dilute as specified when preparing reagent blends.
Quality metrics:
- Repeatability: absolute difference between two results (same operator/lab) should be

Related standards

Other ISO standards

Overview

Key topics and technical requirements

Principle: Convert orthophosphate to a quinoline phosphomolybdate precipitate; quantify phosphorus gravimetrically.
Hydrolysis: Required when phosphate species other than orthophosphate are present; typically reflux about 1 hour.
Reagents: Analytical‑grade reagents only. The standard specifies prepared solutions (A–E) including molybdate, citric acid, nitric acid and quinoline; acetone is used as solvent.
Apparatus: Common lab equipment plus:
- 500 ml wide‑neck conical flask
- Fritted glass crucible (porosity P10 or P16)
- Oven (250 ± 5 °C), desiccator, and a heating device without an open flame
Procedure highlights:
- Add precipitant solution and heat to near‑boiling (~75–80 °C) rapidly.
- Cool, allow precipitate to settle, decant and filter under vacuum.
- Wash repeatedly, transfer to crucible, dry to constant mass at 250 °C and weigh to 0.0001 g precision.
- Add acetone to filtrate and dilute as specified when preparing reagent blends.
Quality metrics:
- Repeatability: absolute difference between two results (same operator/lab) should be

ISO 6598:1985 PDF

Technical details

Abstract

Overview

Key topics and technical requirements

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Abstract

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