Ubbelohde Viscometer with Constant

Updated: 2026-07-18

Overview

The Ubbelohde viscometer, invented by German chemist Leo Ubbelohde, is a suspended-level capillary viscometer renowned for its precision in measuring kinematic viscosity. Unlike Ostwald viscometers, it eliminates surface tension effects through its unique reservoir design, making it ideal for polymer characterization and petroleum testing. Standard models comply with ISO 3105 and ASTM D445 standards, with capillary diameters ranging from 0.3mm to 4.0mm to accommodate various viscosity ranges (0.5-20,000 mm²/s). Industrial laboratories and quality control departments rely on its repeatability of ±0.1% under controlled temperature conditions.

Structure and Working Principle

The instrument consists of a glass tube with precisely manufactured capillary, upper and lower bulbs, and overflow reservoirs. Its suspended-level design ensures liquid head remains constant during measurement, unlike traditional capillary viscometers. Operation follows the Hagen-Poiseuille law: viscosity is calculated from the time taken for a liquid meniscus to pass between two etched marks under gravity. The kinematic viscosity (ν) formula is ν = K×t, where K is the capillary constant (determined via calibration) and t is the efflux time. Temperature control within ±0.01°C is critical for accurate readings.

Key Features

1. Self-draining design eliminates residual liquid errors 2. Multiple capillary sizes (e.g., Cannon-Fenske type) for 0.5-100,000 cSt range 3. Borosilicate 3.3 glass construction withstands chemical corrosion 4. Integrated thermostat jacket compatibility for precise temperature control Advanced models feature automated timing sensors and RS232 data output, reducing human error in industrial settings. The suspended-level principle prevents surface tension interference, especially valuable for polymer solutions where η (intrinsic viscosity) affects molecular weight calculations.

Application Areas

Primary applications include polymer industry (intrinsic viscosity measurement for PET, PVC, polyolefins), lubricant testing (SAE grade classification), and pharmaceutical quality control (syrup viscosity). In petroleum, it determines kinematic viscosity at 40°C and 100°C for ISO/ASTM grading. Research laboratories use modified Ubbelohde viscometers for dilute solution viscosity measurements to calculate molecular weight via the Mark-Houwink equation. Food industries employ it for quality control of edible oils and viscous products.

Maintenance and Precautions

Regular calibration with certified viscosity standards (e.g., NIST-traceable oils) is mandatory - typically every 6 months or after 500 tests. Clean with chromic acid solution or specialized solvents like tetrahydrofuran for polymer residues. Avoid mechanical stress during cleaning; use soft brushes only. Store vertically in padded racks to prevent capillary damage. For temperature-controlled models, verify bath uniformity (±0.01°C) monthly using calibrated thermometers. Always pre-rinse with test liquid to remove solvent traces.

B2B Procurement Guide

Industrial buyers should prioritize: 1. Compliance with required standards (ISO/ASTM) 2. Capillary size matching sample viscosity range 3. Availability of calibration certificates 4. Lead time for custom configurations Bulk purchases (10+ units) typically offer 15-25% discounts. Consider bundled purchases with viscometer stands, temperature controllers, and automated timing systems. For polymer testing, specify 'dilution viscometer' variants with larger reservoirs. Verify manufacturer's glassworking expertise - Schott 3.3 glass is industry-preferred.