Overview
ISO 320:1981 specifies laboratory methods for the determination of sulphur in manganese ores. It defines three procedures: Methods I and II (barium sulphate gravimetric methods) for manganese ores with sulphur > 0.01% (m/m), and Method III (sulphur dioxide titrimetric method) for sulphur determination after combustion. The standard covers principle, reagents, apparatus, sample preparation, stepwise procedure and expression of results, and should be read in conjunction with ISO 4297 and ISO 4296 series for sampling and sample preparation.
Key Topics
- Analytical principles
- Gravimetric conversion of sulphur to sulfate (BaSO4) and determination by ignition and weighing.
- Combustion of sample to release SO2, absorption in solution and titrimetric determination of the resulting sulfuric acid.
- Reagents and materials
- Typical reagents listed include sodium carbonate, sodium peroxide, BaCl2 or Ba(NO3)2 solutions, HCl, HNO3, HF (where required), iodine titrant and starch indicator for titration.
- Use of platinum or nickel crucibles, muffle furnace, combustion tube and gas-absorption train for Method III.
- Operational parameters
- Fusion temperatures and conditions: fusion with sodium carbonate and oxidant at ~800–900 °C (gravimetric), or calcination in O2 at 1 350–1 400 °C or in CO2 at 1 200–1 250 °C (titrimetric).
- Sample mass guidance: typically 0.1–1.0 g for low-sulphur samples, 0.5 g or more for higher sulphur content (Method III guidance in standard).
- Calculation elements: mass of sample and mass of BaSO4 precipitate, conversion factor for BaSO4 → S (factor 0.1374 is specified).
- Quality control
- Procedures for filtration, washing, ignition and weighing of BaSO4 precipitate.
- Tolerances for duplicate determinations are provided for different sulphur concentration ranges.
Applications
- Routine chemical analysis and quality control of manganese ores and concentrates for mining companies, mineral laboratories and metallurgical plants.
- Regulatory compliance, material specification and trade testing where accurate sulphur content is required to assess ore quality and downstream processing impacts (e.g., smelting behaviour, environmental emissions).
- Method selection guidance: gravimetric methods (I/II) for general compositional analysis when sulphur >0.01% (m/m); titrimetric combustion method (III) when gaseous sulphur capture and titration is preferred.
Related Standards
- ISO 4297 - General instructions for chemical analysis of manganese minerals and concentrates (to be read with ISO 320).
- ISO 4296 (parts 1 & 2) - Sampling and sample preparation for manganese ores (referenced for correct sampling and preparation).
Keywords: ISO 320:1981, manganese ores, sulphur determination, barium sulfate gravimetric, sulphur dioxide titrimetric, combustion analysis, analytical methods, chemical analysis.