Ultrasonic attenuation and sound velocity assessment for mixtures of gasoline and organic compounds

The paper presents an experimental method that can be used to identify the possible adulteration in gasoline using ultrasonic attenuation and the ultrasonic propagation velocity. The experiments and measurement uncertainties were assessed according to the Guide to the Expression of Uncertainty in Measurement, JCGM 100:2008. The test samples were mixtures of gasoline and different chemical products: ethanol with gasoline concentrations varying from 52.3% to 80.3% in mass; a ternary mixture of gasoline, ethanol, and hexane, a ternary mixture containing gasoline, ethanol, and toluene; a ternary mixture of gasoline, ethanol, and turpentine; pure gasoline; and commercial gasoline purchased from a local supplier. For the ethanol mixtures, the correlation coefficient between the gasoline concentrations and the ultrasonic propagation velocity was 0.96, and the maximum combined uncertainty was 0.81 m.s(-1). With regard to attenuation, the correlation coefficient was 0.99, and the maximum combined uncertainty was 0.066 dB.cm(-1). Regarding the mixture of gasoline and ethanol, the quantification limit range for a typical maximum concentration (E25 or 75% of gasoline plus 25% of ethanol) was between 73.8% and 76.2%, with expanded uncertainty 0.62 m.s(-1) (coverage probability p = 0.95), considering the propagation velocity as the parameter. In the case of gasoline adulteration with organic solvents, the results were not conclusive, mainly because of the ultrasonic physical-chemical properties of those products and the blends of gasoline and ethanol. Nevertheless, adulteration with those chemicals was easily identifiable for pure gasoline. (C) 2016 Elsevier Ltd. All rights reserved.