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Certification Report for SRM 2214: Density of Iso-octane for Extended Ranges of Temperature and Pressure



Mark O. McLinden, Jolene D. Splett


This report of analysis documents procedures used to obtain certified values and associated uncertainties of the density of iso-octane SRM 2214 over an extended range of temperatures and pressures. This SRM is certified over the temperature range –50˚C to 160˚C and pressure range of 0.1 MPa to 30 MPa; an interpolation model is provided to calculate the density within these ranges. This SRM has a density of 691.853 kg⋅m–3 at t = 20˚C and p = 0.1 MPa. The certification measurements were carried out in a two-sinker magnetic- suspension densimeter. The SRM material is commercial, high-purity iso-octane (2,2,4- trimethylpentane, CAS 540-81-1). Measurements were made on both degassed material and material saturated with nitrogen, and an estimated correction surface (valid over the range –50˚C ≤ t ≤ 100˚C and 0.1 MPa ≤ p ≤ 20 MPa) gives the density difference between the nitrogen-saturated and degassed materials. A thorough analysis of the uncertainties is presented; this includes effects resulting from the experimental density determination, possible degradation of the sample due to time and exposure to high temperatures, dissolved air, uncertainties in the empirical density model, and the sample-to-sample variations in the SRM vials. Also considered is the effect of uncertainties in the user’s temperature and pressure measurements. This SRM is intended for the calibration of industrial densimeters.
Special Publication (NIST SP) - 260-186
Report Number


standard reference material, iso-octane, density, measurement


McLinden, M. and Splett, J. (2016), Certification Report for SRM 2214: Density of Iso-octane for Extended Ranges of Temperature and Pressure, Special Publication (NIST SP), National Institute of Standards and Technology, Gaithersburg, MD, [online], (Accessed June 22, 2024)


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Created October 17, 2016, Updated November 10, 2018