ISO 2977:1997

Overview - ISO 2977:1997 (Aniline point / Mixed aniline point)

ISO 2977:1997 specifies laboratory methods for determination of the aniline point and mixed aniline point of petroleum products and hydrocarbon solvents. The aniline point is defined as the minimum equilibrium solution temperature of equal volumes of aniline and sample; the mixed aniline point uses two volumes of aniline, one volume of sample and one volume of heptane. The standard covers five test methods (including a thin-film and automated method), sample preparation, apparatus, reagents and reporting requirements.

Key topics and technical requirements

• Test methods:
  • Method 1: Conventional air‑jacketed tube - for clear/light-coloured samples with initial boiling points above ambient.
  • Method 2: Thin‑film method - for dark or very dark samples where visual observation in Method 1 is impractical.
  • Methods 3 & 4: For samples that vaporize appreciably at aniline point (Method 4 for small sample volumes).
  • Method 5: Automated/automatic apparatus for ranges covered by Methods 1 and 2.
• Reagents and sample prep:
  • Aniline must be dried and distilled (or ampouled) to meet an internal check with heptane: aniline+heptane gives an aniline point of 69.3 °C ± 0.2 °C.
  • Use drying agents (anhydrous CaSO4 or Na2SO4); heptane minimum purity 99.75%.
  • Remove suspended water and drying agent by centrifuge or filtration; warm waxy samples to homogenize.
• Apparatus and measurement:
  • Specific apparatus described in annexes A–E (air‑jacketed tubes, thin‑film assemblies, small‑scale glassware, automated rigs).
  • Thermometers require calibration traceable to national standards with 0.02 °C resolution.
  • Controlled heating/cooling rates and stirring; water baths are prohibited (aniline is hygroscopic).
• Precision and evaluation:
  • Reporting based on averages of three successive observations if ranges ≤ 0.1–0.2 °C (light vs dark samples).
  • Repeatability (r) and reproducibility (R) given; e.g., r = 0.16 °C (clear samples), R = 0.5 °C (clear samples); higher limits for dark samples.
• Safety: explicit warning-aniline is highly toxic and skin‑absorbable; use goggles and impervious gloves.

Applications - who uses ISO 2977

• Petroleum testing laboratories, QC/QA teams in refining and petrochemical industries.
• R&D and formulation chemists assessing aromatic content (aromaticity) of hydrocarbon mixtures.
• Suppliers and purchasers specifying solvent or fuel acceptance criteria.
• Regulatory or certification bodies requiring standardized physical property data.

Practical value: the aniline/mixed aniline point aids hydrocarbon characterization, helps estimate aromatic fraction, and supports compatibility and solvency assessments.

Related standards (normative references)

• ISO 648:1977 - Laboratory glassware - One‑mark pipettes.
• ISO 2049:1996 - Petroleum products - Determination of colour (ASTM scale).

Keywords: ISO 2977, aniline point, mixed aniline point, petroleum products, hydrocarbon solvents, thin‑film method, aniline point apparatus, test method, repeatability, reproducibility, solvent aromaticity.