Overview
ISO 14719:2011 specifies a spectral photometric method with 1,10‑phenanthroline for the quantitative determination of Fe2+ and Fe3+ in oxidic raw and basic materials used in ceramics, glass and glazes (e.g., feldspar, kaolinites, clay, limestone, quartz refractory materials). The method uses HF/H2SO4 digestion, formation of the orange‑pink 1,10‑phenanthroline–ferrous complex and photometric measurement at 510 nm. Two dissolution/handling procedures (Method A and Method B) are provided to minimise oxidation during analysis.
Key technical topics and requirements
- Scope and limitations
- Intended for oxidic materials and many aluminosilicates; not suitable for reduced materials (silicon carbide, graphite‑magnesia).
- Possible decomposition difficulties with high‑purity alumina and chrome ore.
- Sample preparation
- Grind to <63 µm and dry to constant mass at 110 °C.
- Weigh precise aliquots for digestion (Methods A and B use different sample masses).
- Digestion and preservation
- Acid digestion in hydrofluoric (HF) + sulfuric (H2SO4) matrix.
- Method A: larger sample (≈500 mg), air‑ and light‑tight reaction vessel, nitrogen purge to exclude oxygen and light.
- Method B: small sample (20–30 mg), solution stabilization (nitrilotriacetic acid) in polystyrene cuvettes cooled on ice to limit Fe oxidation.
- Reagents and apparatus
- Use analytical‑grade reagents (1,10‑phenanthroline, hydroxylammonium chloride, ammonium acetate, iron standards).
- For HF‑containing solutions use plastic/PTFE labware; treat glassware appropriately.
- Measurement and calibration
- Form Fe2+–1,10‑phenanthroline complex and measure absorbance at 510 nm.
- Calibrate with iron standard solutions and correct for blank.
- Total iron may be determined photometrically (sum of Fe2+ and Fe3+) or by XRF (ISO 12677) for total Fe2O3.
- Interferences
- Polyvalent ions (e.g., As, Sb) and insoluble precipitates (Pb, Ba sulfates) can interfere; method includes guidance on addressing interferences.
- Sample stability
- Prepared sample solutions are short‑lived (generally not stored for more than one day).
Practical applications and users
- Quality control and R&D labs in:
- Refractory and ceramic manufacturing
- Glass and glaze production
- Raw material qualification (feldspar, clays, kaolinites, quartz)
- Analytical chemists performing wet chemical iron speciation (Fe2+/Fe3+) in mineral and oxide matrices.
- Use cases: controlling iron content which affects colour, melting behaviour and performance of glass, glazes and refractory products.
Related standards (normative/ helpful)
Keywords: ISO 14719:2011, Fe2+ Fe3+ determination, 1,10‑phenanthroline, spectral photometric method, refractory materials, glass and glazes, HF digestion, iron speciation.