A vibrating tube flow densitometer for measurements with corrosive solutions at temperatures up to 723 K and pressures up to 40 MPa

A new version of a vibrating tube flow densitometer has been designed permitting measurements of density differences between two fluids in the temperature range from 298 to 723 K and at pressures up to 40 MPa. The instrument is equipped with a Pt/Rh20 vibrating tube ( 1,6-ram o.d,) and a Pt/Rh 10 transporting tube (I.2-mm o.d.) permitting measurements with highly corrosive liquids. The period of oscillation of the tube is about 7.5 ms, with a typical stability better than 10-4% over about a l-h period over the entire temperature iInterval. The calibration constant K at room temperature is about 530 kg. m -3. ms--ʹ with a temperature coefficient of approximately -0.13 kg. m-3. ms -2. K - and is practically pressure independent. It can be determined by calibration with a reproducibility generally better than 0.1%. The instrument was tested with NaCl(aq) solutions in the temperature range from 373 to 690 K for density differences between sample and reference liquid ranging from 200 to 2 kg. m-~; the corresponding errors are believed to be below 0.3 and 5%. respectively. A highly automated temperature control maintains the temperature of the tube stable to within _+0.02 K.