Overview
ISO 894:1977 - "Surface active agents - Technical sodium primary alkylsulphates - Methods of analysis" is an international standard that specifies analytical methods for quality assessment of sodium primary alkylsulphates (technical surfactants). It applies to technical sodium alkylsulphates in powder, paste or aqueous solution form, provided they are free from extraneous manufacturing by‑products. The standard also includes an annex with a general scheme of analysis.
Key topics and requirements
The standard prescribes the following determinations and related requirements:
- Measurement of pH - performed on a 10% (m/m) solution using the method in ISO 4316; pH below 7.0 indicates instability and often grounds rejection.
- Determination of water content - by Karl Fischer (for products <10% water) or azeotropic distillation (for products >5% water), per ISO 4317 / ISO 4318.
- Free alkalinity or free acidity - titrimetric procedures described in ISO 4314.
- Total alkalinity - titrimetric methods (see ISO 4315); recommended when pH or alkali values indicate discrepancies.
- Matter extractable by light petroleum - isolates non‑ionizing, sulphur‑containing or sulphur‑free substances; includes extraction, drying and gravimetric calculation. Reproducibility between labs is specified (difference should not exceed 1%).
- Matter extractable by diethyl ether after acid hydrolysis - measures combined technical fatty alcohols (and minor sulphonates/fatty acids) following hydrolysis of the aqueous‑alcoholic residue.
- Sodium sulphate and sodium chloride content - determination methods for common inorganic impurities; references provided to specific titrimetric or potentiometric procedures.
- Sampling and sample preparation - laboratory sample preparation references ISO 607 (sample division).
Reagents and apparatus guidance (e.g., solvents, anhydrous sodium sulphate, fractionating columns) and procedural notes on evaporation and loss prevention for volatile fatty alcohols are included.
Applications and users
ISO 894:1977 is intended for:
- Manufacturers of surfactants and detergents for in‑process and final product quality control
- Analytical and QC laboratories testing surfactant raw materials and formulations
- Regulatory and procurement teams specifying acceptance criteria for technical sodium alkylsulphates
- R&D groups characterizing impurity profiles and stability of surfactant batches
Practical benefits include consistent testing protocols, reliable impurity profiling (sodium sulphate, chloride, fatty alcohols), and clearer acceptance/rejection criteria for batches.
Related standards
- ISO 607 (sampling/sample division)
- ISO 2877 (sulphuric acid chloride determination)
- ISO 4314–4318 (methods for alkalinity, acidity, pH, water content)
- Standards for sodium sulphate and chloride determinations referenced within ISO 894
Keywords: ISO 894:1977, sodium primary alkylsulphates, surfactants, methods of analysis, pH, water content, Karl Fischer, alkalinity, fatty alcohols, sodium sulphate, sodium chloride.
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