Overview

ISO 7990:1985 specifies two validated laboratory procedures for the determination of total iron in manganese ores and concentrates. The document defines: Method A (titrimetric after reduction) for samples with total iron from 1 to 25 % (m/m), and Method B (sulfosalicylic acid spectrophotometric) for samples with total iron from 0.2 to 2 % (m/m). The standard is intended to be read in conjunction with ISO 4297 and the ISO 4296 series for sampling and sample preparation.

Both methods cover principle, reagents, apparatus, sampling/sample preparation references, analytical procedure and expression of results, and provide tolerances for parallel determinations so laboratories can assess precision and repeatability.

Key Topics

Principles
- Method A: reduction of Fe(III) to Fe(II) (tin(II) reduction), oxidation of excess reductant, and titration of Fe(II) with potassium bichromate using diphenylamine sulfonate as indicator.
- Method B: formation of a coloured complex between iron and sulfosalicylic acid in alkaline medium; interference from manganese is removed by hydroxylammonium chloride and absorbance is measured near 430 nm.
Scope and applicability
- Method A: suitable for ores/concentrates containing 1–25 % total iron (m/m).
- Method B: suitable for lower-iron products, 0.2–2 % total iron (m/m).
Sample handling & preparation
- Uses ISO 4296/1 and ISO 4296/2 for sampling and sample preparation guidance; includes instructions for dissolution methods for easily and poorly soluble materials and for treatment of residues (fusion, acid attack).
- Typical sample residue incineration and fusion steps (as given in the standard) are included to ensure complete recovery of iron.
Reagents & apparatus
- Method A lists reductants (tin chloride), oxidants (mercury chloride, permanganate) and titrated bichromate solutions and indicator.
- Method B lists sulfosalicylic acid, hydroxylammonium chloride and spectrophotometric measurement equipment.

Applications

ISO 7990:1985 is practical for:

Quality control and specification testing of manganese ores and concentrates.
Acceptance testing during trade and processing when accurate total iron content is required.
Analytical laboratories performing routine compositional assays and inter-laboratory comparisons.

Advantages include clearly defined concentration windows for each method, stepwise sample treatment for difficult matrices, and prescribed expression of results with tolerances for parallel assays.

Related Standards

ISO 4296-1 - Sampling of manganese ores (field sampling)
ISO 4296-2 - Preparation of samples for analysis
ISO 4297 - Manganese ores and concentrates - General instructions for chemical analysis

For implementation, laboratories should follow the reagent, apparatus and procedural details specified in ISO 7990:1985 and cross-reference ISO 4296/ISO 4297 for sampling and sample preparation to ensure representative and reproducible results.

Overview

Key Topics

Principles
- Method A: reduction of Fe(III) to Fe(II) (tin(II) reduction), oxidation of excess reductant, and titration of Fe(II) with potassium bichromate using diphenylamine sulfonate as indicator.
- Method B: formation of a coloured complex between iron and sulfosalicylic acid in alkaline medium; interference from manganese is removed by hydroxylammonium chloride and absorbance is measured near 430 nm.
Scope and applicability
- Method A: suitable for ores/concentrates containing 1–25 % total iron (m/m).
- Method B: suitable for lower-iron products, 0.2–2 % total iron (m/m).
Sample handling & preparation
- Uses ISO 4296/1 and ISO 4296/2 for sampling and sample preparation guidance; includes instructions for dissolution methods for easily and poorly soluble materials and for treatment of residues (fusion, acid attack).
- Typical sample residue incineration and fusion steps (as given in the standard) are included to ensure complete recovery of iron.
Reagents & apparatus
- Method A lists reductants (tin chloride), oxidants (mercury chloride, permanganate) and titrated bichromate solutions and indicator.
- Method B lists sulfosalicylic acid, hydroxylammonium chloride and spectrophotometric measurement equipment.

Applications

ISO 7990:1985 is practical for:

Quality control and specification testing of manganese ores and concentrates.
Acceptance testing during trade and processing when accurate total iron content is required.
Analytical laboratories performing routine compositional assays and inter-laboratory comparisons.

Advantages include clearly defined concentration windows for each method, stepwise sample treatment for difficult matrices, and prescribed expression of results with tolerances for parallel assays.

Related Standards

ISO 4296-1 - Sampling of manganese ores (field sampling)
ISO 4296-2 - Preparation of samples for analysis
ISO 4297 - Manganese ores and concentrates - General instructions for chemical analysis

ISO 7990:1985 PDF

Technical details

Abstract

Overview

Key Topics

Applications

Related Standards

Related standards

Abstract

Overview

Key Topics

Applications

Related Standards

Related standards

Manganese ores and concentrates -- Methods of chemical analysis -- General instructions

Manganese ores -- Sampling -- Part 2: Preparation of samples

Manganese ores -- Sampling -- Part 1: Increment sampling