ISO 4689-2:2017

Overview

ISO 4689-2:2017 specifies a validated combustion/titration method for the determination of sulfur content in iron ores. The procedure applies to natural iron ores, iron ore concentrates and agglomerates (including sinter products) with sulfur contents from 0.002 % to 0.25 % (mass fraction). Results are not affected by fluoride. The standard defines sample preparation, reagents, apparatus, test procedure, calculation, precision and reporting requirements for reliable sulfur analysis.

Key topics and technical requirements

• Principle: Sample is mixed with tungsten(VI) oxide (WO3) and combusted at 1 200 °C ± 25 °C in a resistance furnace using nitrogen as carrier gas. Evolved SO2 is absorbed in dilute hydrochloric acid containing starch and potassium iodide (KI) and titrated continuously with a standard potassium iodate (KIO3) solution.
• Applicable range: 0.002 % – 0.25 % S (mass fraction).
• Test portion mass:
  • 0.002–0.100 % S → 1.0 g test portion
  • 0.100–0.25 % S → 0.5 g test portion
• Reagents & solutions: analytical-grade reagents; KIO3 standard (0.001042 mol/L) where 1 mL = 0.10 mg S. Use tungsten oxide, tin(II) chloride (if chlorides present), Mg(ClO4)2 and NaOH-coated silica in drying train.
• Apparatus essentials: resistance furnace, refractory combustion tube/boat or cartridge, drying tower, flowmeter, multi-hole bubbler and burette (or micro-syringe/piston burette for very low S < 0.005 %).
• Chloride handling: when chloride is present or suspected, pass combustion gases through a tin(II) chloride absorption tube to remove chlorine before SO2 absorption.
• Quality control: include blank tests and parallel analysis of a certified reference material; carry out at least duplicate independent determinations. The standard provides repeatability, between-laboratory precision and procedures for acceptance of analytical values.
• Safety: warns about hazardous operations and materials; users must establish appropriate health and safety practices.

Applications and users

ISO 4689-2:2017 is used by:

• Mining and iron ore laboratories for QA/QC of raw ore, concentrates and sinter.
• Metallurgical and pelletizing plants monitoring sulfur for process control.
• Certification and reference-material laboratories validating analytical results.
• Regulatory bodies and trade labs where standardized sulfur measurement is required for commercial specifications.

Keywords: ISO 4689-2:2017, iron ores, sulfur determination, combustion/titration method, sulfur analysis, iron ore concentrates, sinter products, analytical method.

Related standards

• ISO 4689 series (other parts, e.g., combustion/infrared method)
• ISO 3082 (sampling and sample preparation)
• ISO 7764 (preparation of predried test samples)
• ISO 2596 (hygroscopic moisture)
• ISO Guide 35 (reference materials)
• ISO 385 / ISO 648 / ISO 1042 (laboratory glassware)