ISO 2829:1973

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.