Overview
ISO 8214:1985 specifies a gravimetric method for determining inorganic sulfate content in all types of commercial washing powders and surfactant-containing detergents. The method removes ethanol‑soluble organic material, separates silicates when present, precipitates sulfates as barium sulfate (BaSO4), and quantifies sulfates by ignition and weighing of the BaSO4 residue. Results are expressed as percentage of sodium sulfate (Na2SO4).
Key topics and requirements
- Sample preparation: laboratory sample division per ISO 607 and a test portion (~10 g) for analysis.
- Removal of organics: extraction of ethanol‑soluble matter by Soxhlet extraction or repeated hot‑ethanol treatment in a beaker.
- Silicate treatment: if silicates/insolubles are present, the ethanol‑insoluble residue is treated with hydrochloric acid and evaporated to dryness repeatedly, then re‑dissolved and filtered to obtain a silicate‑free solution.
- Sulfate precipitation: sulfates in the final filtrate are precipitated using barium chloride under controlled pH (methyl orange indicator, neutralized with ammonia then acidified).
- Filtration and ignition: the BaSO4 precipitate is filtered (porcelain crucible or ashless filter), washed until free of chlorides (silver nitrate test), converted to a tared platinum or porcelain crucible, heated to 900 °C, and weighed to 0.001 g precision.
- Calculation: mass of BaSO4 is converted to equivalent Na2SO4 using the conversion factor (0.6086) to report sulfate content as % Na2SO4.
- Apparatus & reagents: Soxhlet extractor, one‑mark 1 000 ml volumetric flask (ISO 1042), filtering crucibles, furnace (900 °C), ethanol, HCl, BaCl2 solution, ammonia, methyl orange, silver nitrate.
- Quality assurance: method is suited to routine laboratory use; interlaboratory precision was assessed during standard development.
Applications and who uses it
- Quality control labs in detergent and washing powder manufacturing for routine sulfate content verification.
- Formulation and R&D teams checking raw material influence on inorganic sulfate levels.
- Regulatory and compliance laboratories verifying product labeling and conformity to specifications.
- Test houses and standards bodies using the prescribed gravimetric approach as a reference or comparative method.
Practical benefits include a robust, interference‑resistant gravimetric endpoint and applicability to commercial detergent matrices containing silicates and other common additives.
Related standards
- ISO 607 - Surface active agents and detergents: sampling and sample division.
- ISO 8215 - Determination of total silica (relevant when the ethanol‑insoluble residue is retained for silica analysis).
- ISO 1042 - Volumetric flasks (glassware specification).
Keywords: ISO 8214:1985, surface active agents, washing powders, inorganic sulfates, gravimetric method, barium sulfate precipitation, detergent analysis, sulfate determination, Soxhlet extraction.