ISO 1392:1977

Overview

ISO 1392:1977 specifies a general laboratory method for the determination of the crystallizing (crystallisation) point of liquids and liquefied samples across a wide temperature range (about −50 °C to +250 °C). The principle is simple: the sample is cooled under defined conditions and the temperature is observed during crystallization. The standard replaces ISO Recommendation R 1392-1970 and is intended for routine determinations in testing and quality‑control laboratories.

Key Topics

• Scope and principle: Applicable from about −50 °C to +250 °C. Determination is by controlled cooling and observation of temperature changes during crystallization.
• Sample condition: Tests can be carried out on the sample "as received", on a dried sample, or both. The required sample state must be specified in the specific test method for the material.
• Water and high-moisture samples: Samples with high water content (e.g., pastes) must be dried before testing.
• Apparatus and reagents: Typical equipment includes a crystallization tube (approx. 25 mm external diameter, 150 mm length), an outer protection tube, an agitator with a loop (~20 mm diameter), a precision thermometer (graduated to 0.1 °C with known maximum scale error 0.1 °C), Dewar vessels with appropriate refrigerant (CO2/acetone, ice/water or water), and a heated bath for higher temperature ranges. Reagents cited include acetone, solid carbon dioxide, ice and dried calcium sulfate (CaSO4).
• Procedure notes: Fill the crystallization tube to about 60 mm; position the thermometer so its bulb is about 15 mm above the tube bottom. Agitation is used during cooling; supercooling (surfusion) can occur and, if excessive, the test should be repeated using seeding to suppress it. The crystallizing point is recorded as the highest temperature reached after crystallization, rounded to 0.1 °C and corrected for instrument errors.

Applications

• Quality control and specification testing of oils, melts and other liquid materials where crystallization behaviour matters.
• Comparative laboratory measurements to ensure consistent batch release, processing temperature limits, or storage requirements.
• Use in material testing methods that reference a standardized crystallizing point determination.

Related Standards

• ISO 1392:1977 supersedes ISO Recommendation R 1392-1970.
• Specific product test methods will indicate whether the determination must be made on the sample as received or after drying, and will specify any alternative drying or preparation procedures (oven drying at 60 °C, vacuum drying, etc.).

Reporting: Test reports should include the method reference, sample state (as received or dried), the crystallizing point to 0.1 °C, any corrections applied, and any deviations from the standard procedure.