Overview
ISO 9088:1997 specifies a pyknometric method for determining the true density of carbonaceous cathode blocks and prebaked anodes used in aluminium production. The method measures density by immersion in xylene using a calibrated pycnometer after controlled degassing under vacuum. This standard defines required reagents, apparatus, sample preparation, calibration and calculation procedures to achieve repeatable and reproducible density results.
Key topics and technical requirements
- Scope: True density determination in xylene of cathode blocks and prebaked anodes for aluminium manufacture.
- Sample preparation:
- Drill/cut sample, crush and grind to particle size ≤ 63 μm.
- Dry sample at 120 °C ± 2 °C for 8 hours, then cool in a desiccator.
- Test portion: 5.0 g ± 0.1 g.
- Apparatus & reagents:
- Pyknometer (type 3, Gay‑Lussac), 25 ml capacity (ISO 3507 referenced).
- Degassing apparatus with vacuum pump, oil trap and manometer (maintain residual pressure 1.3 kPa ± 0.3 kPa for high precision; 2.6 kPa ± 0.3 kPa acceptable for lower precision).
- Reagents: xylene (commercial grade, ~0.86 g/ml), ethanol (95%), acetone, concentrated sulfuric acid, distilled/de‑gassed water.
- Safety note: xylene is hazardous (skin contact and inhalation risk).
- Calibration & measurement:
- Calibrate pyknometer volume at 25 °C ± 0.05 °C using degassed water; mean of 8–10 determinations recommended.
- Determine xylene density by the same calibrated pyknometer.
- Degas sample in xylene under vacuum, allow settling (≥ 30 min), then weigh to 0.1 mg accuracy.
- Calculation & precision:
- Density calculated from pyknometer mass/volume measurements and sample mass; result reported to three decimal places.
- Precision: repeatability r = 0.004 g/ml, reproducibility R = 0.006 g/ml.
Applications and users
- Quality control and acceptance testing in aluminium smelters and carbon electrode producers.
- Materials testing laboratories evaluating carbonaceous materials, cathode blocks and prebaked anodes.
- Suppliers certifying product density for performance (electrical/thermal properties, porosity control).
- R&D groups and standards committees working on electrode materials and process optimization.
Related standards
- ISO 3507 - Pyknometers (reference for pyknometer types/calibration).
- ISO 8007 - Sampling from cathodic blocks and prebaked anodes.
- ISO 5725 - Precision of test methods (precision data derivation).
Keywords: ISO 9088:1997, pyknometric method, density in xylene, pycnometer, carbonaceous materials, cathode blocks, prebaked anodes, aluminium production, density determination, QC testing.
