Advanced calibration, adjustment, and operation of a density and sound speed analyzer

Influence of the alkyl group on thermophysical properties of carboxylic acids in 1-butyl-3-methylimidazolium thiocyanate ionic liquid at various temperatures

“…The estimated uncertainty in measurements of density, sound velocity and temperature were less than ±2 Á 10 À5 g Á cm À3 , ±0.8 m Á s À1 and ±0.02 K, respectively. The sound velocity is measured using a propagation time technique [33]. The sample is sandwiched between two piezoelectric ultrasound transducers.…”

“…One transducer emits sound waves through the sample-filled cavity (frequency around 3 MHz) and the second transducer receives those waves. Thus, the sound velocity is obtained by dividing the known distance between transmitter and receiver by the measured propagation time of the sound waves [33]. The estimated uncertainty in excess molar volume, isentropic compressibility, and deviation in isentropic compressibility was ±0.005 cm 3 Á mol À1 , ±2 Á 10 À8 Pa À1 and ±0.7 Á 10 À8 Pa À1 , respectively.…”

Measurement and prediction of speeds of sound of fatty acid ethyl esters and ethylic biodiesels

“…The calibrants used were ultra-pure water and dodecane with certified density values issued by H §D Fitzgerald, with expanded uncertainties of 0.01 kg m À3 (coverage factor k = 2, providing a 95% level of confidence). The use of this pair of calibrating fluids allowed a close bracketing of the densities measured, the importance of which has recently been emphasized by Fortin et al [32] As the temperature range of certified density values for dodecane does not cover values higher than 323.15 K, an extrapolation of those values had to be made. However, a careful analysis of results based on comparison between direct density values (taken from direct readings of the densimeter) and final values obtained from the calibration procedure allowed a reassurance about the validity of that extrapolation.…”

Excess thermodynamic properties of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate and N-octyl-2-pyrrolidone from T=(298.15 to 323.15)K at atmospheric pressure

“…Table 4 illustrates the important thermodynamic properties of the ILs, namely, isentropic compressibility The term isentropic means that as the sound wave pass through a fluid, the pressure and temperature fluctuate within each microscopic volume but the entropy of the system as a whole remains constant. This condition holds true when we measure the speed of sound using a low frequency generator (DSA 5000 M transducer produces approximately 3 MHz frequency) but at high frequency (>100 MHz) there is velocity dispersion as well as absorption of sound waves due to the coupling with molecular processes within the fluid [35][36][37]. As expected, isentropic compressibility decreases with increasing IL concentration in the mixture and increases with increasing temperature.…”