Overview
ISO 4715:1978 defines a quantitative laboratory method for determining the evaporation residue of essential oils. The method removes the volatile fraction of an essential oil by heating on a boiling water bath and quantifies the non‑volatile residue by direct weighing. This straightforward gravimetric technique supports routine quality control and purity assessment of essential oils.
Key Topics
- Principle: Evaporate the volatile fraction on a boiling water bath; weigh the remaining residue and express it as a percentage of the test portion.
- Sample amount: The standard specifies weighing the test portion to 0.001 g accuracy. Unless otherwise stated for a specific oil, use 5 ± 0.05 g of essential oil.
- Apparatus:
- Boiling water bath with a perforated plate (holes of diameter 70 mm) and a water level maintained approximately 50 mm below the lid during the test.
- Anti‑wrinkling glass capsule of uniform thickness (1 to 1.5 mm) sized per the figure in the standard to hold the sample.
- Analytical balance for weighing to 0.001 g.
- Desiccator with an effective drying agent (e.g., silica gel) for cooling capsules before weighing.
- Procedure highlights:
- Prepare the sample in accordance with ISO 356 and sampling per ISO 212.
- Place the weighed capsule on the boiling water bath and maintain a calm atmosphere without interruption for the time specified for the particular essential oil.
- After the specified heating time, transfer the capsule to the desiccator, allow it to cool, and weigh the residue to 0.001 g.
- Calculation: Express the evaporation residue as a mass percentage: (mass of residue / mass of test portion) × 100, reported with one decimal place.
- Reporting: The test report must record the method used, the result, any optional or non‑standard procedural details, and any incidents that may have affected the result. Complete sample identification information must be included.
Applications
- Quality control testing of essential oils to detect high levels of non‑volatile residues.
- Batch release and specification verification in flavor, fragrance, and cosmetic raw materials.
- Comparative purity checks and supplier verification.
Related Standards
- ISO 212 - Essential oils: Sampling (referenced for sample collection).
- ISO 356 - Essential oils: Sample preparation for testing (referenced for sample handling).
This ISO method provides a reproducible, gravimetric approach for measuring residue on evaporation in essential oils. It is intended for laboratories performing routine analysis where a clear, standardized procedure is required for consistent quality assessment.
