Overview
ISO/TR 11422:1996 is a Technical Report by ISO/TC 102 (Iron ores) that recommends laboratory procedures for dissolution of iron ores using acid digestion or alkali fusion (including sinter fusion). The report summarizes interlaboratory studies and provides practical, consolidated procedures for preparing test solutions from typical iron ore test portions (notably 2 g, 1 g and 0.5 g acid-digestion routines). It also assesses advantages and disadvantages of acid vs alkali approaches for analytical methods and trace-element determinations.
Key topics and technical requirements
- Purpose: standardize sample dissolution practice for reliable chemical and trace-element analysis of iron ores.
- Procedures covered:
- Acid digestion methods for 2 g, 1 g and 0.5 g test portions, including reagents, apparatus and stepwise procedure.
- Alkali fusion and alkali sinter fusion options, with discussion of flux-to-sample ratios and variants (including an “8‑4‑5” low-flux procedure).
- Typical reagents specified: hydrochloric, nitric, sulfuric and hydrofluoric acids; sodium carbonate; sodium tetraborate. Water quality in accordance with ISO 3696 is required.
- Apparatus highlights: 250 ml glass beakers, platinum crucibles, calibrated hotplate (to give 95°C and 105°C settings in specified acid depth), muffle furnace or burner.
- Key procedural details (acid digestion examples):
- Initial digestion covered at ~95°C (about 1 h); if residue remains, raise to ~105°C avoiding boiling.
- Addition of HNO3 and small H2SO4, then evaporation to dryness and further heating for 15 min.
- Filtration, drying/ashing of filter paper and residue, HF treatment to remove silica, ignition (750–800°C), fusion with Na2CO3/Na2B4O7 at ~1000°C, dissolve melt in HCl and combine with main solution to a defined volume.
- Assessment points:
- Alkali fusion offers one-step dissolution and avoids extensive residue treatment but raises solution salt concentrations (which can interfere with AAS/ICP techniques).
- Flux-to-sample ratios are critical - the report documents lower-flux options (e.g., ~2.4:1) and higher ratios (3:1, 4:1) where acceptable.
Applications and users
- Intended for metallurgical and mineral analysis laboratories, QA/QC labs in mining, geochemistry and environmental labs performing iron ore chemical and trace-element assays.
- Useful for analysts establishing sample-preparation SOPs, method validation, and interlaboratory comparisons where harmonized dissolution is required.
- Helps laboratories choose between acid digestion (preferred for larger test portions in trace-element work) and alkali fusion (preferred for faster one-step dissolution when matrix salts are manageable).
Related standards
Keywords: ISO/TR 11422, iron ore dissolution, acid digestion, alkali fusion, sinter fusion, sample preparation, analytical methods, test portion, trace element analysis.