Comments on temperature calibration and uncertainty estimate of the vibrating tube densimeter operated at atmospheric pressure

0558885 - ÚT 2023 RIV GB eng J - Journal Article
Prokopová, Olga - Blahut, Aleš - Čenský, Miroslav - Součková, Monika - Vinš, Václav
Comments on temperature calibration and uncertainty estimate of the vibrating tube densimeter operated at atmospheric pressure.
Journal of Chemical Thermodynamics. Roč. 173, October (2022), č. článku 106855. ISSN 0021-9614. E-ISSN 1096-3626
R&D Projects: GA ČR(CZ) GA19-05696S; GA ČR(CZ) GA22-03380S
Institutional support: RVO:61388998
Keywords : calibration * density * uncertainty estimate * vibrating tube densimeter * viscosity effect
OECD category: Thermodynamics
Impact factor: 2.6, year: 2022
Method of publishing: Limited access
https://doi.org/10.1016/j.jct.2022.106855

Vibrating tube densimeter (VTD) is a popular instrument providing a quick and accurate measurement of density for large variety of liquids and gases. Sensitive commercial instruments have resolution of down to 0.001kg⋅m3 and their accuracy is declared to reach 0.007kg⋅m3 under ideal conditions at temperatures close to ambient.However, the uncertainty of the obtained data can be significantly higher when it comes to measurements over wider temperature range. We present calibration procedure for a commercial borosilicate glass VTD (namely Anton Paar DMA 5000 M) over the temperature range from 275 to 363K together with an uncertainty analysis.The approach is similar to that of Fritz et al. [J. Phys. Chem. B 104 (2000) 3463] when the density can be obtained from the relative oscillation period PQ, damping difference ΔD0 and calibration parameters A, B,V1, and V2 as ρ = A(1 + V1ΔD0 + V2ΔD20 )PQ2B. Temperature dependencies of the calibration parameters A and B were determined from a series of precise measurements with ultrapure water and dry air correlated to the densities calculated from the IAPWS-95 equation of state for water and the IAPWS G8-10 guideline for humid air. The calibration procedure was verified on measurements with toluene, ethanol, ethylene glycol, and glycerol. A detailed analysis of the uncertainty budget resulted in the standard uncertainty around 0.030kg⋅m3 for typical low-viscosity samples. In case of highly viscous liquids such as low-temperature ethylene glycol or glycerol, the uncertainty can reach 0.060kg⋅m3 or even 0.14kg⋅m3, respectively, at the dynamic viscosity exceeding 50mPa⋅s. Other influences are also discussed, such as the relation between fluid viscosity and damping, the isotopic composition of the calibration water, the measurement procedure covering VTD cleaning and filling, and the effect of water contained in samples.
Permanent Link: https://hdl.handle.net/11104/0332618