Overview
EN ISO 7579:2009 - "Dyestuffs - Determination of solubility in organic solvents - Gravimetric and photometric methods" (CEN adoption of ISO 7579:2009) specifies two validated laboratory methods to determine the solubility of dyestuffs in organic solvents. The standard applies to dyestuffs that remain chemically unchanged, non-volatile and stable under the test drying conditions. It describes sample preparation, mixing, centrifugation and two measurement routes (gravimetric and photometric) to establish a saturation concentration expressed in g/L.
Key topics and requirements
- Two test methods
- Gravimetric method: recommended for volatile solvents (boiling point < 120 °C). Solubility is determined by measuring non‑volatile matter after evaporating solvent and drying.
- Photometric method: recommended for less volatile solvents (boiling point > 120 °C). Solubility is determined by spectrophotometric absorbance relative to a standard solution.
- Scope limits
- Suitable for concentration range 1–1 000 g dyestuff per litre of solvent (higher concentrations allowed if viscosity permits).
- Not suitable for measuring insoluble impurities in dyestuffs.
- Test conditions
- Mixing at (23 ± 2) °C for 3 hours, followed by centrifugation (typical rotor speeds ≈ 2 000–3 000 min⁻¹) to obtain a clear supernatant.
- Gravimetric drying temperatures up to about 150 °C for many metal‑complex dyestuffs; solvent density at 23 °C must be known.
- Apparatus & precision
- High‑precision balance (0.0001 g), pipettes, volumetric flasks, centrifuge tubes, mechanical shaker, drying oven, spectrophotometer and ultrasonic bath as required.
- Normative references
Practical applications
- Quality control and batch acceptance testing for pigment and dye manufacturers.
- Formulation development and solvent selection in paints, varnishes, inks, plastics and coatings.
- Comparative solubility screening for R&D and troubleshooting (e.g., solubility-driven color strength or dispersion issues).
- Supporting regulatory and technical dossiers where defined solubility data in organic solvents is required.
- Laboratory analysts and QC chemists in the colorant, coatings and printing industries
- Product development teams assessing solvent–dyestuff compatibility
- Standards and compliance personnel preparing technical documentation
Related standards
EN ISO 7579:2009 provides a practical, repeatable approach for reliable dyestuff solubility determination in organic solvents, helping laboratories generate comparable solubility data for formulation, quality control and regulatory use.
