ISO 21078-2:2006

Overview

ISO 21078-2:2006 specifies an acid extraction method for the determination of boron(III) oxide (B2O3) in binder components of aluminosilicate refractory products. The standard applies to refractories containing less than 1% (mass fraction) B2O3 and defines sample preparation, extraction, blanking, and three analytical determination routes: sodium hydroxide titrimetry, ICP/AES, and curcumin (Rothocyanine) spectrophotometry.

Key topics and technical requirements

• Scope and applicability: Intended for B2O3 as a binder component in aluminosilicate refractories (<1% B2O3).
• Sampling and sample preparation:
  • Crushing and sieving to defined sizes (e.g., 6.7 mm, 300 µm, 106 µm) per ISO 3310-1.
  • Drying and weighing of test portions (typically 5.0 g for extraction).
• Acid extraction procedure:
  • Extraction with dilute hydrochloric acid (1 + 1) and warm water, standing ~30 min with stirring.
  • Filtration and wash with dilute HCl (1 + 50); final dilution to prepare the test solution.
  • Preparation of a blank solution by repeating extraction without sample.
• Analytical determination methods:
  • Sodium hydroxide titrimetry: removal of silicic acid, use of D(–)-mannitol, bromocresol purple indicator and calculation using an equivalent factor.
  • ICP/AES: measurement of B emission (e.g., 249.678 nm or 208.959 nm if Fe overlap occurs), calibration with B2O3 standards and blank matrix addition; strict calibration correlation (r ≥ 0.999).
  • Curcumin (Rothocyanine) spectrophotometry: alternative colorimetric method described for lower concentrations.
• Quality assurance and reporting:
  • Duplicate extractions, blank corrections, calibration checks, mid-point validation for ICP, and expression of results (mean of determinations) per ISO 31-0 rounding rules.

Practical applications and users

ISO 21078-2 is relevant for:

• Refractory manufacturers and quality-control laboratories verifying binder composition.
• Analytical labs performing material certification for ceramic and refractory industries.
• R&D teams developing binder formulations or assessing low-level boron additions.
• Regulatory and procurement teams requiring standardized test methods for material acceptance.

Benefits include reproducible quantification of low-level B2O3, compatibility with multiple analytical platforms (titrimetry, ICP/AES, spectrophotometry), and defined sample-handling procedures to minimize variability.

Related standards

• ISO 21078-1 - Determination of total boric oxide in oxidic materials for ceramics, glass and glazes (other part of the series).
• Normative references used by ISO 21078-2: ISO 31-0, ISO 836, ISO 3310-1, ISO 3696.

Keywords: ISO 21078-2, boron(III) oxide determination, acid extraction method, refractory binder analysis, ICP/AES boron, mannitol titrimetry, curcumin spectrophotometry, refractory quality control.