Overview
ISO 4785:1997 specifies requirements, dimensions and construction details for straight-bore glass stopcocks for general laboratory use. It defines two series of nominal bore sizes, ground‑zone geometry and surface-finish limits, material recommendations and marking/designation rules to ensure reliable, interchangeable stopcocks used in chemical and analytical laboratories.
Key topics and technical requirements
- Two series of nominal bores
- Series I: 1, 1.5, 2.5, 4, 6, 10 mm
- Series II: 1, 1.5, 2, 3, 4, 5, 6, 8, 10 mm
- Ground zone taper and finish
- Taper: one increment in diameter per ten increments of axial length (tolerance ±0.006 on diameter increment)
- Surface roughness (centreline average height): ≤ 1 µm, preferably - ** (example: Stopcock ISO 4785, 4 - 18.8)
- The large end diameter of the ground zone must be permanently marked on the barrel.
Applications and who uses this standard
- Laboratory glassware manufacturers - design and produce stopcocks that are dimensionally interchangeable and meet quality/tolerance requirements.
- Quality control and inspection teams - verify taper, surface finish, material class and marking for conformity.
- Procurement and specification writers - cite ISO 4785 when specifying general‑purpose stopcocks for research, teaching and industrial labs.
- Calibration/test laboratories and standards bodies - use as a reference for compatibility with other lab glassware.
Related standards
Relevant cross‑references cited by ISO 4785 include:
- ISO 3585 (Borosilicate glass 3.3)
- ISO 719 (Hydrolytic resistance test & classification)
- ISO 4803 (Borosilicate glass tubing)
- ISO 468 (Surface roughness parameters)
- ISO 383 (Interchangeable conical ground joints) and other laboratory glassware standards listed in Annex A
Keywords: ISO 4785, laboratory glassware, glass stopcocks, straight‑bore stopcock, borosilicate glass 3.3, ground zone, stopcock dimensions, stopcock tolerances, stopcock designation.
