Overview
ISO 619:1981 specifies two validated laboratory methods for the determination of chromium in manganese ores: the diphenylcarbazide photometric method (Method I) and the silver persulphate titrimetric method (Method II). The standard defines scope, reagents, apparatus, sample preparation and calculation procedures, and requires reading in conjunction with ISO 4297 (chemical analysis instructions) and ISO 4296 (sampling).
Key topics and technical requirements
- Two-method approach by concentration
- Method I (photometric): for chromium < 0.1% (m/m). Forms a red‑violet diphenylcarbazide‑chromate complex measured at 520–530 nm using a photoelectric absorptiometer with a green filter.
- Method II (titrimetric): for chromium > 0.1% (m/m). Oxidation by ammonium persulphate (with AgNO3 catalyst), reduction with ammonium iron(II) sulphate, and back‑titration of excess Fe(II) with standardized KMnO4.
- Sample preparation
- Test samples crushed to a particle size not exceeding 100 µm and air‑dried under laboratory conditions.
- Fusion of test portion with sodium carbonate + sodium peroxide in nickel or corundum crucibles in a muffle furnace (Method I: 700–800 °C; Method II: 650–750 °C).
- Reagents and solutions
- Photometric reagents include diphenylcarbazide (prepared fresh), ammonium persulphate, and hydroxyquinoline for vanadium removal if required.
- Titrimetric reagents include silver nitrate, ammonium persulphate, ammonium iron(II) sulphate, and potassium permanganate standardized against sodium oxalate.
- Calculation and reporting
- Chromium content expressed as percentage by mass on the dry basis.
- Photometric results may be obtained by calibration graph or comparison method; titrimetric results use formulae accounting for titers and aliquots.
- Quality control
- The standard includes procedures for reagent standardization and specifies permissible tolerances for duplicate determinations based on chromium concentration.
Applications and practical value
ISO 619 is designed for analytical and quality control laboratories analyzing manganese ores and concentrates. Typical uses:
- Trade specification testing and contract disputes.
- Mine exploration and production quality control.
- Metallurgical feedstock analysis for smelting and refining.
- Regulatory and compliance testing where certified analysis procedures are required.
Who should use this standard
- Analytical chemists and laboratory managers in mining and mineral processing.
- Quality assurance personnel at ore trading companies and smelters.
- Standards professionals and regulatory bodies assessing ore composition.
Related standards
- ISO 4297 - Manganese ores and concentrates: Methods of chemical analysis (general instructions).
- ISO 4296 (Parts 1 & 2) - Sampling and sample preparation of manganese ores.
Keywords: ISO 619, manganese ores, chromium determination, diphenylcarbazide photometric method, silver persulphate titrimetric method, chromium content analysis, ore chemical analysis.