Overview
EN ISO 787-13:2019 (ISO 787-13:2019) defines general laboratory test methods for the determination of water‑soluble sulphates, chlorides and nitrates in pigments and extenders. Published by CEN/ISO, this part of the ISO 787 series provides step‑by‑step analytical procedures, required reagents and apparatus, sampling references and result expression rules for quality control and specification testing of pigment raw materials and finished products.
Key topics and technical requirements
- Scope: A single, general method for measuring the water‑soluble fractions of sulphates, chlorides and nitrates in pigments and extenders.
- Reagents: Analytical‑grade chemicals and distilled (or equivalent) water. The standard lists specific reagents (with CAS identifiers) such as hydrochloric acid, 0.01 mol/L silver nitrate, barium chloride, potassium chromate, Devarda’s alloy and Nessler’s reagent.
- Apparatus: Typical laboratory equipment plus specified items such as a sintered‑silica filter crucible (porosity P10/P16), Nessler cylinder (50 ml) and distillation apparatus.
- Sampling: Representative sampling is required per ISO 15528 to obtain the test portion.
- Procedures:
- Sulphates: acidify a clear aqueous extract, precipitate as barium sulphate, filter, ignite and weigh the BaSO4 precipitate to calculate SO4 content.
- Chlorides: add potassium chromate indicator to the extract and titrate with 0.01 mol/L silver nitrate (Mohr method); potentiometric end‑point is an alternative.
- Nitrates: reduce nitrates with Devarda’s alloy under alkaline conditions, distil the released ammonia into acidified receiver, then colour‑match with Nessler’s reagent against ammonium standards.
- Results: Formulae for converting analytical measurements to mass fractions are provided; results are reported to two decimal places.
- Document controls: Replaces the 2002 edition; includes updated terms referencing ISO 18451‑1 and added bibliography.
Applications and who uses it
- Pigment and extender manufacturers for raw material specification and incoming quality control.
- Paints and coatings producers to verify contaminant levels that affect formulation, stability and performance.
- Analytical and QA/QC laboratories performing routine or contract testing of pigments, fillers and dyestuffs.
- Regulatory and procurement teams that need standardized test data for material acceptance and compliance.
- R&D teams assessing the effect of soluble ions on product properties (corrosion, conductivity, dispersion).
Related standards
- ISO 787 series (other parts covering pigment test methods)
- ISO 15528 - Sampling for paints, varnishes and raw materials
- ISO 18451‑1 - Terminology for pigments, dyestuffs and extenders
Keywords: EN ISO 787-13:2019, ISO 787-13, pigments and extenders, water-soluble sulphates, chlorides, nitrates, Mohr titration, barium sulfate precipitation, Devarda’s alloy, Nessler’s reagent, pigment test methods.