Overview
ISO 548:1981 (second edition) defines a barium sulphate gravimetric method for the determination of barium oxide (BaO) content in manganese ores. This International Standard replaces the 1975 edition and is intended to be read in conjunction with ISO 4297 (general chemical analysis instructions). The method provides laboratory procedures from sample preparation to expression of results, supporting reliable gravimetric analysis for quality control and materials characterization.
Key Topics
- Principle: Fusion of a test portion with sodium–potassium carbonate, extraction of the fusion in water, dissolution of barium carbonate in hydrochloric acid, removal of silicic acid and precipitation of barium as barium sulphate. The precipitate is filtered, ignited and weighed to calculate BaO content.
- Sample preparation: Use a test sample crushed to a size not exceeding 100 µm and air-dried under laboratory conditions (see ISO 4296/2 for sample prep; ISO 4296/1 for increment sampling).
- Test portion and fusion: Typical test portion is 1–2 g fused with anhydrous sodium potassium carbonate; fusion temperatures and times (as given in the Standard) ensure complete decomposition and extraction.
- Reagents and apparatus: The Standard specifies reagents such as hydrochloric and sulphuric acids, hydrofluoric acid, hydrogen peroxide, ammonium acetate, sodium carbonate, and silver nitrate, and recommends ordinary laboratory apparatus including platinum crucibles.
- Procedure highlights: Extraction, repeated acid evaporations, controlled precipitation of BaSO4, washing of precipitate (hot solutions), ignition of the filter residue and final weighing to determine BaO content.
Applications
This method is used by:
- Analytical laboratories performing chemical analysis of manganese ores and concentrates.
- Quality control teams in mining and mineral processing facilities monitoring BaO impurity levels.
- Regulatory or standards bodies requiring standardized gravimetric determination for comparative testing.
Practical benefits include: reproducible gravimetric results, clear reagent and apparatus lists for lab implementation, and alignment with ISO sampling and analysis guidance (ISO 4297, ISO 4296 series).
Related Standards
- ISO 4297 - Manganese ores and concentrates: Methods of chemical analysis - General instructions (to be read with ISO 548).
- ISO 4296/1 - Increment sampling (sampling guidance referenced by ISO 548).
- ISO 4296/2 - Preparation of samples (sample preparation requirements referenced by ISO 548).
Note: ISO 548:1981 specifies the full procedural sequence including sample size, fusion conditions, reagent grades and apparatus. Laboratories should follow the Standard text for precise temperatures, reagent concentrations and procedural tolerances when implementing the gravimetric determination of BaO.
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