Overview
ISO 385:2005 - "Laboratory glassware - Burettes" specifies metrological and construction requirements for an internationally acceptable series of laboratory burettes. It defines accuracy classes, measurement conditions (reference temperature 20 °C, with 27 °C as an alternative for tropical use), material and construction criteria, and test methods for delivery volume, delivery time and leakage. The standard is aligned with the volumetric glassware principles in ISO 384 and excludes piston burettes (see ISO 8655-3).
Key topics and technical requirements
- Accuracy classes and types
- Two accuracy grades: Class A (including Class AS with a 30 s waiting time) and Class B.
- Burettes are either no-waiting-time type (A, B) or with a 30 s waiting time (AS).
- Metrological requirements
- Delivered volume (Ex) is adjusted with water; final reading at the reference temperature.
- Reference temperature: 20 °C (alternative 27 °C for tropical use).
- Maximum permissible errors are specified by nominal capacity and subdivision (see Table 1). Example values: 1 ml Class A ±0.006 ml, 10 ml Class A ±0.02 ml, 100 ml Class A ±0.20 ml.
- Material and construction
- Glass quality: chemical resistance and thermal properties at least HGB3 per ISO 719; free from visible defects and internal stress.
- Dimensional limits (scale length, overall length, distances from zero line and stopcock) and optional features (auto-zero, reservoirs) are specified.
- Stopcocks, jets and leakage
- Stopcocks must permit smooth, precise control; conventional all-glass stopcocks usually use a 1:10 taper.
- Leakage limits: with water and stopcock closed, ≤ 1 scale subdivision in 20 min for Class A/AS (≤ 2 for Class B); for grease-free stopcocks, tighter limits apply (e.g., half subdivision in 50 min for Class A/AS).
- Jet geometry and finish requirements to avoid turbulence and air trapping.
- Graduation, meniscus and markings
- Graduation patterns, position of lines and visibility, and rules for setting the meniscus and waiting time are specified to ensure reproducible readings.
Applications and users
ISO 385 is essential for:
- Laboratory instrument manufacturers and suppliers designing or certifying volumetric burettes.
- Calibration and testing laboratories performing accuracy verification and leakage tests.
- Analytical and educational laboratories performing titrations and volumetric analysis that require traceable, standardized burettes.
- Quality assurance and regulatory bodies assessing conformity of laboratory glassware.
Keywords: ISO 385, burettes, laboratory glassware, volumetric glassware, burette calibration, accuracy classes, stopcock leakage, delivery volume.
Related standards
- ISO 384 - Principles of design and construction of volumetric glassware
- ISO 719 - Glass - Hydrolytic resistance (HGB classification)
- ISO 4787 - Volumetric glassware - Methods for use and testing of capacity
- ISO 8655-3 - Piston burettes (related piston-type instruments)
