Overview
ISO 3507:1999 specifies requirements for laboratory pyknometers (pycnometers) used to determine the densities of liquids. It defines a series of standard tube- and flask-type pyknometers for general laboratory use, excludes specialized devices for particular products, and gives construction, marking and measurement requirements to ensure reliable volume calibration and repeatable density determinations. Annex A illustrates an adjustment device for the Reischauer type.
Key topics and technical requirements
- Types and sizes: Six types are specified (Lipkin, Sprengel, Gay‑Lussac, Reischauer, Hubbard and a ground‑in‑thermometer design) with a defined series of nominal capacities for each type.
- Reference conditions: The standard reference temperature for capacity verification is 20 °C (27 °C recommended where tropical ambient conditions apply). Actual capacity must be stated with its verification temperature.
- Material and construction: Pyknometers must be made of glass with suitable hydrolytic resistance (at least HGB3) and appropriate thermal stability (includes borosilicate glass 3.3). Stoppers, caps and taps must have compatible thermal properties. Shapes, neck design and stopper fit are specified to avoid trapped liquid and ensure repeatable filling.
- Capacity, tolerances and calibration: The standard defines actual capacity (volume of water at the reference temperature) and nominal capacity, and sets maximum permissible differences and measurement‑uncertainty requirements (capacity must be determined at the 95% confidence level).
- Graduation and markings: Graduation lines must be clean, permanent and ≤ 0.3 mm thick, with defined layouts for each type. Permanent markings required include nominal capacity (or determined capacity to 0.001 ml plus verification temperature), unit of volume, manufacturer, and identification marks to ensure correct stopper/thermometer positioning.
- Thermometers and accessories: For the ground‑in‑thermometer pyknometer the standard calls for enclosed‑scale thermometers meeting ISO 386 and for a capillary side tube/cap design where applicable.
Applications and users
- Primary use: Accurate determination of liquid density and specific gravity in analytical and quality control laboratories.
- Who uses it: Laboratory managers, analytical chemists, calibration laboratories, glassware manufacturers, and instrument suppliers who produce or verify pyknometers and related volumetric apparatus.
- Practical benefits: Ensures interchangeability, traceable volume calibration, reproducible density measurements, and conformity across labs and suppliers.
Related standards
- ISO 383 - Interchangeable conical ground joints
- ISO 384 - Principles for volumetric glassware
- ISO 386 - Liquid‑in‑glass thermometers
- ISO 719 - Hydrolytic resistance of glass
- ISO 3585 - Borosilicate glass 3.3
Keywords: ISO 3507, pyknometer, pycnometer, laboratory glassware, density determination, volumetric calibration, borosilicate glass, ISO standard.
