Overview
ISO 2598-2:1992 specifies a reduced molybdosilicate spectrophotometric method for determining silicon (Si) content in iron ores. The method applies to natural iron ores, concentrates and agglomerates (including sinter) with silicon contents from 0.1 % to 5.0 % by mass and is particularly suited to ores containing fluorine (fluorine does not interfere). The procedure converts silicate to a molybdosilicate complex, reduces it to molybdenum blue, and measures absorbance spectrophotometrically at about 600 nm.
Key topics and technical requirements
- Sample preparation and size
- Predried laboratory sample prepared per ISO sampling/preparation standards; typical test portion ≈ 0.50 g (after predrying).
- Decomposition by fusion
- Fusion of the test portion with sodium tetraborate or a specified fusion mixture (carbonate + tetraborate) at ~1 100 °C, followed by dissolution in dilute nitric acid.
- Formation and reduction of the molybdosilicate complex
- Addition of ammonium molybdate to form the molybdosilicate complex and reduction with ascorbic acid to yield molybdenum blue.
- Spectrophotometric measurement
- Measure absorbance of molybdenum blue at approximately 600 nm; correct readings against a blank/background solution.
- Calibration and quality control
- Calibration with silicon standard solutions and background solution prepared similarly to samples.
- Use of blank tests, duplicate determinations, and analyses of certified reference materials for acceptance (repeatability and between-laboratory tolerances are specified).
- Reagents and apparatus
- Analytical-grade reagents (sodium tetraborate, ammonium molybdate, oxalic and ascorbic acids, dilute nitric and sulfuric acids) and a spectrophotometer suitable for ~600 nm.
Practical applications and users
ISO 2598-2 is intended for:
- Laboratory analysts in mineral analysis and metallurgy performing Si assays on iron ore feedstocks, concentrates and sinter products.
- Mining company QA/QC teams verifying ore chemistry for beneficiation and smelting control.
- Research and regulatory laboratories requiring standardized, comparable silicon determinations.
- Metallurgists evaluating silicon’s effect on blast-furnace charge and product quality.
Benefits include reliable quantification in fluorine-bearing ores, standardized calibration and acceptance criteria, and clear procedural controls for reproducible results.
Related standards
Keywords: ISO 2598-2, iron ores, silicon determination, reduced molybdosilicate spectrophotometric method, molybdenum blue, spectrophotometry 600 nm, fusion with sodium tetraborate, ore analysis, QA/QC.
