ISO 4322:1977

Overview

ISO 4322:1977 - Non‑ionic surface active agents: Determination of sulphated ash (gravimetric method) specifies a laboratory gravimetric procedure to determine the sulphated ash content of non‑ionic surfactants. The method involves calcination of a measured test portion in the presence of sulphuric acid and subsequent weighing of the residue as sulphate. It is intended for routine quality control and compositional analysis of non‑ionic surface active agents.

Key topics and technical requirements

• Scope: Gravimetric determination of sulphated ash in non‑ionic surface active agents (general application to surfactants).
• Primary principle: Calcination of the test portion with sulphuric acid and conversion of inorganic residues to sulphates for gravimetric weighing.
• Reagents and apparatus:
  • Platinum crucible (100 ml capacity)
  • Furnace controllable at 775 ± 25 °C
  • Gas burner and a 6 N sulphuric acid solution free from ash
  • Ammonium nitrate (NH4NO3)
  • Distilled (or equivalent) water and analytical‑grade reagents
• Sample preparation: Laboratory sample prepared and stored according to ISO 607 (sample division).
• Test portion: About 30 g of homogenized sample is placed in the tared crucible (weighing to 0.1 mg resolution).
• Procedure highlights:
  • Initial controlled burning on a low flame until spontaneous combustion is established; avoid overheating to prevent spattering.
  • After carbonaceous residue forms, add ammonium nitrate crystals and a small volume (~0.5 ml) of sulphuric acid to wet the residue.
  • Heat to dull red, complete combustion, then finish calcination in the furnace at 775 ± 25 °C for 20–30 min.
  • Cool in a desiccator and weigh; repeat heating/cooling cycles until two successive weighings agree within 1 mg.
• Safety: Perform combustion in a fume cupboard and use safety goggles.
• Precision: Interlaboratory reproducibility: difference between two labs should not exceed 0.1% for sulphated ash levels near 1%.

Applications and users

ISO 4322 is used by:

• Quality control and analytical laboratories in the surfactant, detergent and chemical manufacturing sectors
• Raw material inspection and incoming goods testing
• Regulatory and standards bodies verifying product composition and compliance
• R&D teams evaluating formulation purity and inorganic residue content

Practical uses include specification compliance checks, batch release testing, impurity monitoring, and comparative quality assessment of non‑ionic surface active agents.

Related standards

• ISO 607 - Surface active agents: sampling and division of laboratory samples (referenced for sample preparation)
• Users should consult ISO 607 when preparing the laboratory sample for ISO 4322 analysis.

Keywords: ISO 4322, sulphated ash, non‑ionic surface active agents, gravimetric method, surfactant analysis, ash determination, quality control.