Overview
ISO/TS 4689-1:2023 - "Iron ores - Determination of sulfur content - Part 1: Barium sulfate gravimetric method" specifies a laboratory gravimetric procedure to determine sulfur in iron ores, concentrates and agglomerates (including sinter) over the mass-fraction range 0.01 % to 3.9 %. The Technical Specification updates the decomposition step from older acid/alkali melt methods to a soda–zinc oxide (Na2CO3–ZnO) semi-melting approach and describes sample preparation, reagents, apparatus, and quality checks required for reliable gravimetric determination of sulfate as barium sulfate.
Key Topics and Requirements
- Scope & applicability: Natural iron ores, concentrates and agglomerates (sinter products) within 0.01–3.9 % S.
- Sampling & sample size: Laboratory sample particle size typically −100 µm; use −160 µm for ores with significant combined water or oxidizable compounds (see ISO 3082, ISO 7764).
- Decomposition: Semi-melt test portion with a sodium carbonate–zinc oxide flux (blend Na2CO3 and ZnO by mass ratio 3:2) at 780 °C ± 20 °C for 60 min to liberate sulfate.
- Leaching & separation: Water leach with electromagnetic stirring (or ultrasonic extraction), filtration through a 0.2 µm membrane or sand-core filter; remove interferences (Cr, Sn, P) using hydrogen peroxide, citric acid and calcium carbonate as needed.
- Precipitation & gravimetry: Convert sulfate to BaSO4 by acidity adjustment and addition of barium chloride (BaCl2·2H2O); filter, dry and weigh precipitate to quantify sulfur.
- Reagents & apparatus: Lists analytical-grade reagents (HF, HCl, H2SO4, H2O2, citric acid, ethanol, AgNO3, etc.), membrane filters, glass suction funnel and sand-core filter.
- Quality control: Duplicate determinations, blank tests, certified reference material in each run, check tests, and procedures for repeatability/permissible tolerance and result acceptance (Annexes A–C provide flow-sheets and precision data).
- Test portion guidance (Table 1): e.g., for 0.01–0.100 % S use 5.000 g test portion with 10.0 g flux; for >0.100–2.00 % use 1.000 g & 8.0 g flux; for >2.00–4.00 % use 0.500 g & 5.0 g flux.
Applications and Users
- Who uses it: Analytical laboratories, mining and beneficiation plants, quality-control teams in iron and steel production, port and trading laboratories, environmental and regulatory testing labs.
- Practical uses: Product quality specification (sinter, concentrates), furnace process control (minimizing sulfur-related problems), compliance reporting, incoming/outgoing material certification and interlaboratory method harmonization.
Related Standards
- ISO 3082 - Sampling and sample preparation procedures for iron ores
- ISO 2596 - Determination of hygroscopic moisture in analytical samples
- ISO 7764 - Preparation of predried test samples for chemical analysis
Keywords: ISO/TS 4689-1:2023, iron ores sulfur determination, barium sulfate gravimetric method, soda–zinc oxide semi-melting, sulfur content testing.