Determination of the force transmission error in a single-sinker magnetic suspension densimeter due to the fluid-specific effect and its correction for use with gas mixtures containing oxygen

•The magnetic suspension coupling induces errors in single-sinker densimeters.•Paramagnetic fluids affects density measurements in single-sinker densimeters.•Fluid-specific effect of the force transmission error is experimentally determined.•The apparatus-specific constant depends on temperature and density. Density measurements from single-sinker magnetic suspension densimeters need to be corrected to compensate for the magnetic effects of the measuring cell materials and the fluid on the coupling transmission system. While the magnetic effect of the densimeter materials can be easily determined, the fluid effect requires the calculation of an apparatus-specific constant, ερ. In this work, the apparatus-specific constant of the single-sinker magnetic suspension densimeter at the University of Valladolid has been determined by using two alternative methods. The first method, which uses density data for the same fluid and conditions and different sinkers, yielded a value of ερ = 4.6·10−5. The second method, obtained from measurements with pure oxygen, yielded a value of ερ = 8.822·10−5. The second value is considered as more reliable, as the first method presents inherent limitations in this case.