ISO 21079-2:2008

Overview

ISO 21079-2:2008 specifies validated wet chemical analysis methods for AZS refractories - materials composed of alumina (Al2O3), zirconia (ZrO2) and silica (SiO2) - with 5 % to 45 % ZrO2. It provides traditional laboratory procedures as an alternative to X‑ray fluorescence (XRF) (see ISO 12677) for both finished refractory products and raw materials. The standard is Part 2 of the ISO 21079 series and complements Part 1 (apparatus, reagents, dissolution) and Part 3 (FAAS and ICP‑AES). Note: ISO 21079-2:2008 is not applicable to MgO‑based refractories.

Key topics and technical requirements

• Scope and applicability: AZS refractories and raw materials containing 5–45 % ZrO2; alternative to XRF methods.
• Silicon(IV) oxide (SiO2): molybdenum‑blue photometric methods (including combined dehydration/coagulation + molybdenum blue) for different concentration ranges.
• Aluminium oxide (Al2O3): cation‑exchange column separation or cupferron separation followed by CyDTA (chelation) and zinc back‑titration.
• Zirconium oxide (ZrO2): gravimetric determination using mandelic acid (also accounts for hafnium oxide).
• Other oxide determinations: Fe2O3, TiO2, CaO, MgO and methods described for each.
• Alkali analysis: Na2O and K2O by flame photometry.
• Chromium(III) oxide (Cr2O3): colorimetric determination using diphenylcarbazide.
• Quality control elements: calibration graphs, blank tests, repeatability limits, and calculation/reporting of mass fractions.
• Normative cross‑references: ISO 21079-1, ISO 21079-3, ISO 12677, ISO 26845 and related wet‑chemistry standards.

Practical applications and users

ISO 21079-2:2008 is used by:

• Laboratory analysts performing chemical composition testing of AZS refractories.
• Quality control and production teams in refractory manufacturing for acceptance testing and process control.
• Raw material suppliers and inspectors verifying feedstock composition.
• R&D and failure analysis teams requiring confirmatory wet‑chemical data or where XRF/ICP access is limited.
• Certification bodies and testing laboratories needing standardized methods alternative to instrumental techniques.

Practical benefits include robust, well‑documented procedures for labs that require classical wet chemistry approaches, cross‑checking of XRF/ICP results, and analytical routes when instrumental methods are unavailable or unsuitable.

Related standards

• ISO 21079-1:2008 (Apparatus, reagents, dissolution)
• ISO 21079-3:2008 (FAAS and ICP‑AES methods)
• ISO 12677 (XRF method for refractories)
• ISO 26845 (general requirements for wet chemical and AAS/ICP methods)
• ISO 21587-2 (wet chemical analysis for aluminosilicate refractories)

Keywords: ISO 21079-2:2008, wet chemical analysis, AZS refractories, alumina zirconia silica, ZrO2 analysis, XRF alternative, SiO2 determination, Al2O3 titration, mandelic acid gravimetry, flame photometry.