Oscillating-U-Tube Densitometer
Definition
An instrument that measures liquid density from the resonant frequency of a liquid-filled U-shaped tube; precision of ±0.0001 g/cm³, widely used for pharmaceutical and food-fraud liquid analysis.
- Measures
- Liquid density
- Principle
- Resonant frequency of a liquid-filled U-shaped tube
- Typical precision
- ±0.0001 g/cm³
- Common use
- Pharmaceutical and food-fraud liquid analysis
Common questions
How is density used to detect food or pharmaceutical fraud?+
A liquid's density is compared against the known reference value for the genuine product; dilution, substitution, or adulteration typically shifts density outside the accepted range even when the liquid looks visually identical.
What sample volume does this technique usually require?+
Oscillating-U-tube instruments generally need only a small liquid sample, often under a millilitre, and the measurement is non-destructive, so the remainder of the sample stays available for further testing.
Related terms
- ASTM E2365
- The American Society for Testing and Materials standard for forensic comparison of glass by density; specifies temperature control, calibration, and precision requirements...
- Bromoform-Bromobenzene System
- The reference liquid mixture used in forensic density-gradient columns and sink-float tests; bromoform (2.890 g/cm³) and bromobenzene (1.495 g/cm³) mix in variable...
- Density
- Mass per unit volume (ρ = m/V), expressed in g/cm³ or kg/m³; a physical property used to compare and discriminate glass, mineral,...
- Density-Gradient Column
- Glass column filled with stepwise layers of liquids of decreasing density (commonly bromoform 2.89 g/cm3 and bromobenzene 1.50 g/cm3 mixed in known...
- DFSS
- Directorate of Forensic Science Services, India; issues the Forensic Laboratory Manual that governs glass and soil examination procedures, including the bromoform-based density...
- ENFSI ENG3-2013
- The ENFSI Glass Expert Working Group guideline for glass comparison casework; specifies the examination sequence, within-source variation requirements, statistical comparison framework, and...
- Hydrostatic Weighing
- Density measurement exploiting Archimedes' principle; the apparent weight loss of a solid submerged in a liquid of known density equals the weight...
- Neutral Buoyancy
- The condition in which a solid object's density exactly matches the density of the surrounding liquid; the object neither sinks nor rises...
- Pycnometry
- Absolute density measurement using a calibrated-volume flask; the density of a solid is calculated from the mass of liquid displaced when the...
- Sink-Float Test
- Qualitative density screening in which a solid fragment is immersed in a liquid of adjustable density until neutral buoyancy is achieved; the...
- Stokes Settling Formula
- The equation v = 2r²g(ρₛ - ρ_f) / 9η relating the settling velocity of a spherical particle to its radius, the density...