Overview
ISO 12979:1999 specifies a laboratory method for determining the atomic carbon/hydrogen (C/H) ratio of the quinoline‑insoluble (QI) fraction isolated from coal‑tar pitch for electrodes used in aluminium production. The standard describes both: (a) a procedure to isolate QI material in a form suitable for analysis (hot‑quinoline digestion, pressure‑filtration, hot‑toluene washing and drying) and (b) the subsequent carbon and hydrogen analysis by combustion with trapping and weighing of CO2 and H2O to calculate the atomic C/H ratio.
Key topics and technical requirements
- Scope: Determination of the atomic C/H ratio of QI material isolated from electrode pitch (coal‑tar pitches). The isolation procedure is not a substitute for ISO 6971 when determining QI content.
- Sample preparation: Representative sampling per ISO 6257; grind to pass a 250 μm sieve.
- Isolation: Digest ~1 g pitch in ~25 ml quinoline at 70–80 °C for 20 min; use a heated pressure‑filtration unit (47 mm membrane discs, PTFE, 0.2 μm nominal pore); perform multiple hot‑quinoline and hot‑toluene washes and dry at 105–110 °C.
- Combustion analysis: Weigh aliquot of isolated QI material, combust in oxygen, trap and weigh CO2 and H2O; calculate atomic C/H ratio from measured carbon and hydrogen contents using relative atomic masses.
- Apparatus & reagents: Quinoline (freshly distilled), toluene, inert gas supply, thermostatted hotplate, hot‑air blower, membrane filters, magnesium perchlorate and NaOH on silicate (for drying/CO2/H2O traps), silver mesh/wool, quartz wool, O2 supply and a carbon/hydrogen analyzer.
- Safety & quality: Contains explicit safety warnings for quinoline, solvents and perchlorates; specifies equipment temperature/pressure limits and good laboratory practice. Precision (repeatability/reproducibility) and reporting requirements are included.
Applications and users
ISO 12979:1999 is used for:
- Quality control in electrode pitch manufacture and incoming material inspection for the aluminium industry.
- Analytical laboratories performing carbon/hydrogen characterization of carbonaceous materials.
- R&D teams studying pitch composition and insoluble fractions.
- Compliance and specification drafting where the atomic C/H ratio of QI material is a material property of interest.
Keywords: ISO 12979:1999, C/H ratio, quinoline‑insoluble, electrode pitch, coal‑tar pitch, aluminium production, carbonaceous materials, pressure‑filtration, combustion analysis.
Related standards
- ISO 6257 - Sampling of pitch for electrodes.
- ISO 6971 - Determination of quinoline‑insoluble content (QI content).
- ISO 565, ISO 4788 - Laboratory equipment (sieves, graduated cylinders) referenced in the method.
This standard is primarily a technical laboratory procedure for characterizing QI material and supports material specification and quality assurance in the aluminium electrode supply chain.