Overview
ISO 2829:1973 specifies a spectrophotometric method for the determination of phosphorus content in aluminium oxide (alumina) used for aluminium production. The method - also approved by IUPAC - is applicable to products with phosphorus contents greater than 0.0005 % (m/m). It uses alkaline fusion to prepare the sample, formation of a phosphomolybdic complex, solvent extraction, reduction to a coloured species, and spectrophotometric measurement near 730 nm.
Key Topics and Requirements
- Scope and sensitivity
- Applicable to alumina samples with P > 0.0005 % (m/m).
- Sample preparation
- Preparation of a solution from a test portion by alkaline fusion: either with a mixture of sodium carbonate and borid (as stated in the original text) or with sodium carbonate and sodium tetraborate.
- Dissolution of the cooled molten mass in nitric acid.
- Adjustment of an appropriate aliquot to pH 2 before complex formation.
- Complex formation and extraction
- Formation of a phosphomolybdic complex in an acid medium (sulphuric acid).
- Extraction of the complex into 2‑methylpropan‑1‑ol (isobutanol) as the organic phase.
- Reduction and measurement
- Reduction of the extracted complex by tin(II) chloride in the organic phase to produce the reduced phosphomolybdate chromophore.
- Spectrophotometric measurement of the reduced complex at a wavelength of about 730 nm for quantification.
- Quality control
- Use of appropriate aliquots, blanks, and calibration standards is implied for accurate quantitation (users should follow good laboratory practice for calibration and QC).
Applications and Who Uses It
- Alumina and aluminium producers - quality control of feedstock to control phosphorus levels that can affect smelting and metal quality.
- Analytical and metallurgical laboratories - routine and reference analyses for phosphorus in alumina samples.
- Standards organizations and testing laboratories - method reference for method validation and inter-laboratory comparisons.
- Reagent and instrument suppliers - supplying appropriate chemicals (e.g., tin(II) chloride, extraction solvents) and spectrophotometers optimized for ~730 nm measurements.
Practical value: the method provides a sensitive, IUPAC-approved route to quantify trace phosphorus in alumina, supporting product specification compliance and process control in aluminium production.
Related Standards
- ISO 2829:1973 is an established reference for phosphorus analysis in alumina and is cross-referenced by laboratories using spectrophotometric phosphomolybdate chemistry. Users often consult complementary ISO methods for other impurity determinations in aluminium oxide and general laboratory quality standards.