Overview
ISO 5068-1:2025 - "Brown coals and lignites - Determination of moisture - Part 1: Indirect gravimetric method for total moisture" specifies laboratory procedures to measure the total moisture of brown coals and lignites. The document defines two indirect gravimetric procedures: a single-stage nitrogen‑flushed drying method and a two-stage method (air‑dry stage followed by nitrogen drying). This second edition updates terms, references and the test report and replaces ISO 5068-1:2007.
Key Topics and technical requirements
- Methods covered:
- Single-stage method: finely prepared sample dried to constant mass at 105 °C to 110 °C in a nitrogen atmosphere.
- Two-stage method: coarse sample air‑dried (ambient or 30–40 °C), then crushed and dried at 105–110 °C under nitrogen to determine residual moisture; total moisture is the sum of both losses.
- Atmosphere & gases: use high‑purity dry nitrogen with maximum oxygen ≤ 30 µl/l; nitrogen flow through the oven ≈ 15 oven volumes per hour.
- Apparatus & materials: nitrogen‑flushed oven, drying cabinet (30–40 °C), non‑corrodible trays/dishes, balances sensitive to 0.01 g and 0.001 g, and drying tower packed with magnesium perchlorate or silica gel (magnesium perchlorate is a strong oxidizer - safety warning included).
- Sample preparation & sizes: single‑stage sample crushed to pass 3.15 mm sieve and divided to 500 g; two‑stage coarse crush to pass 20 mm and divided to 2 kg (or as specified by particle-size rules).
- End‑point criteria: constant mass defined by successive mass changes