Overview
ISO 5976:2025 - "Rare earth - Determination of loss on ignition in rare earth products - Gravimetric method" specifies a standardized gravimetric procedure for measuring loss on ignition (LOI) in solid rare earth materials. The method applies to rare earth oxides, carbonates and oxalates and gives clear instructions on sampling, sample preparation, ignition, weighing and result calculation to improve comparability of LOI data across laboratories and supply chains.
Key topics and technical requirements
- Scope and LOI ranges: Applicable LOI ranges are 0.10 %–15.00 % for rare earth oxides, 25.00 %–80.00 % for carbonates, and 35.00 %–75.00 % for oxalates.
- Principle: Gravimetric determination - LOI is the mass loss after ignition to constant mass.
- Apparatus: Required equipment includes an analytical balance readable to 0.1 mg, porcelain or platinum crucibles with lids, desiccator, oven (105 °C ± 5 °C) and furnace (950 °C ± 10 °C).
- Sampling and handling: Samples must be sealed and weighed promptly after opening to avoid moisture uptake.
- Test portion masses: Recommended test masses - 2.00 g (oxides), 30.00 g (carbonates), 20.00 g (oxalates).
- Procedure highlights:
- Pre‑treat crucibles by heating at 950 °C for 30 min until constant mass.
- For high‑moisture carbonates/oxalates, dry at 105 °C for 1 h before ignition.
- Ignite samples at 950 °C for 1 h, allowing lids to be offset for gas release; cool in desiccator and weigh to constant mass.
- Perform duplicate determinations (parallel test).
- Calculation and reporting: LOI expressed as percentage by mass; formulas provided for “as received” and dry‑basis (correction using moisture from ISO 24548). Test reports must identify sample, method (ISO 5976:2025), results, and any deviations or unusual features.
- Precision and reproducibility: Precision data and permissible tolerances are included (interlaboratory study results available in Annex A). The standard references ISO 5725‑2 and ISO/TR 21074 for precision evaluation.
Applications and users
ISO 5976:2025 is intended for:
- Quality control laboratories in rare earth mining and processing;
- Chemical analysis labs performing compositional or material performance testing;
- Producers, traders and consumers of rare earth oxides, carbonates and oxalates who require consistent LOI data for specification compliance, product certification and trade dispute resolution;
- Research institutions and interlaboratory calibration studies.
Benefits include improved accuracy of LOI measurements, reduced variability between labs, and greater confidence in material specifications used in electronics, magnets, catalysts and other rare‑earth applications.
Related standards
- ISO 5725‑2 - Accuracy (trueness and precision) of measurement methods
- ISO 22444‑1 - Rare earth vocabulary (minerals, oxides, compounds)
- ISO 24548 - Moisture determination (used to correct LOI to dry basis)
- ISO/TR 21074 - Guidance on permissible tolerances
For the full official text and detailed procedures, obtain ISO 5976:2025 from the ISO store or your national standards body.