ISO 756-1:1981

Overview

ISO 756-1:1981 (also published as ISO 756/1-1981) specifies general methods of test for propan-2-ol (isopropyl alcohol) for industrial use. This Part 1 gives sampling and laboratory instructions and details the standardized test methods used to assess key quality attributes of industrial propan-2-ol: density at 20 °C, boiling range (distillation characteristics), dry residue after evaporation, colour, water content and carbonyl compounds (aldehydes and ketones). ISO 756-1:1981, together with ISO 756-2 and ISO 756-3, replaced ISO Recommendation R 756‑1968.

Key topics and technical requirements

• Sampling and sample storage
  • Laboratory sample to be kept in a clean, dry, tight glass bottle with a screw cap and polyethylene seal.
  • Recommended sample volume: minimum 750 mL to complete the test series.
• Density at 20 °C
  • Determination method referenced to ISO 758 (liquid chemicals - density at 20 °C).
• Boiling range / Distillation
  • Use the method in ISO 918 for distillation characteristics, with propan-2-ol specific modifications.
  • Heating rate adjusted so the time before the first distillate drop is 7–12 minutes.
  • Temperature readings corrected for barometric pressure: 0.025 °C per mbar deviation from 1013 mbar.
• Dry residue after evaporation
  • Follow ISO 759 (residue after evaporation on a water bath).
• Colour measurement
  • Use the Hazen/Platinum-Cobalt scale method per ISO 2211.
• Water content
  • Methods per ISO 760, typically Karl Fischer titration for accurate moisture determination.
• Aldehydes and ketones (carbonyl compounds)
  • Determination per ISO X343/3, with procedural notes (sample purification of ethanol, titration details). Results are calculated using prescribed formulas and expressed in mg/kg or percentage as required.
• Test report requirements
  • Each report must include sample identification, reference to the method used, result expressions, and notes on any deviations or unusual observations.

Practical applications and users

• Quality control laboratories in chemical manufacturing and distribution.
• Producers and purchasers of industrial propan-2-ol (isopropyl alcohol) specifying product acceptance criteria.
• Regulatory agencies and testing laboratories performing standard conformity assessments.
• R&D and formulation teams requiring validated test procedures for raw material qualification.

Related standards

• ISO 758 - Density at 20 °C
• ISO 918 - Distillation characteristics (with propan-2-ol modifications)
• ISO 759 - Residue after evaporation
• ISO 760 - Karl Fischer water determination
• ISO 2211 - Colour (Hazen/PCU)
• ISO X343/3 - Carbonyl compounds (aldehydes and ketones)
• ISO 756-2 and ISO 756-3 - Complementary parts covering acidity (titrimetry) and water miscibility

Keywords: ISO 756-1:1981, propan-2-ol, isopropyl alcohol, methods of test, density at 20 °C, distillation, Karl Fischer, colour measurement, aldehydes, ketones, industrial alcohol testing.