ISO 10251:2006

Overview

ISO 10251:2006 specifies standardized laboratory methods for determining the moisture content of copper, lead, zinc and nickel concentrates. Moisture is defined as the percentage mass loss of a test portion when dried under the conditions given in the standard. The document sets requirements for sampling, drying, weighing and calculation of moisture content, and provides procedures when concentrates are susceptible to oxidation, decomposition or sublimation. Note: ISO 10251:2006 is not applicable to drying samples intended for determination of volatile elements such as mercury or sulfur.

Key topics and technical requirements

• Drying conditions: Test portions are dried at 105 °C ± 5 °C (forced-air oven or inert-gas circulation) and dried to constant mass where possible.
• Test portion size: Minimum 1 kg per test portion; trays should allow sample spread to a thickness < 30 mm.
• Weighing precision: Top-loading balance with minimum precision about 0.01 % (per Table 1).
• Drying cycles: An initial drying period (16 h suggested for many concentrates) followed by repeated 4 h cycles until two successive mass readings agree within 0.05 % of the initial test portion mass.
• Special handling methods (Methods 1–5): Guidance on choosing drying approach when concentrates:
  • can be dried to constant mass,
  • are susceptible to oxidation (use inert atmosphere or common sample),
  • lose organics during prolonged drying,
  • cannot reach constant mass (interrupt drying after a specified period),
  • gain mass after drying (oxidation risk).
• Annexes:
  • Annex A - test for susceptibility to oxidation, decomposition and sublimation
  • Annex B - handling cohesive or very wet concentrates (predrying)
  • Annex C - example worksheet for results
• Sampling linkage: Moisture sampling and processing must follow ISO 12743 to ensure representativeness.

Practical applications and users

• Used by mining companies, metallurgical labs, assay houses, quality control teams, and commodity traders to:
  • determine moisture for mass and value calculations,
  • prepare samples for accurate chemical analysis,
  • establish saleable dry-mass or adjust freight and processing charges.
• Practical value: ensures consistent, reproducible moisture determination across laboratories and supports unbiased metal content estimates when preparing predried or hygroscopic samples.

Related standards

• ISO 12743 - Sampling procedures for concentrates (referenced for sampling and representativeness)
• ISO 9599 - Hygroscopic moisture determination (used for volatile element analyses and ambient drying)

Keywords: ISO 10251:2006, moisture content, copper concentrate, drying to constant mass, sample drying, oxidation, inert atmosphere, concentrate moisture determination.