EN ISO 7579:2009 PDF

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
  • Links to ISO 787‑2 (volatile matter), ISO 2811‑1 (density by pyknometer) and ISO 15528 (sampling).

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.

Who uses EN ISO 7579:2009

• 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

• ISO 787‑2 (determination of matter volatile at 105 °C)
• ISO 2811‑1 (pyknometer density method)
• ISO 15528 (sampling)

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.