Complexity of natural systems causes that results of experimental studies are often ambiguous and extremely unrewarding in interpretation. To overcome this difficulty, relative simple model systems may be investigated in order to provide physical grounds for further discussion. This study deals with adiabatic compressibility of liquid ternary system consisting of phenanthrene, toluene and heptane. Increase of heptane concentration in the mixture changes considerably the partial compressibility of phenanthrene, from common positive value in pure toluene up to clearly negative ones. This is most probably because of selfassociation of phenanthrene due to strong London forces. Heptane seems to promote the self-association. These feature of the investigated system suggests its usefulness in studies of flocculation of asphaltenes from crude oils.
There was presented in the paper the theoretical discussion about the ultrasonic relaxation process related to energy transfer between translational and vibrational degrees of freedom as well as with the existing of chemical isomerism. The part of the paper describes several ultrasonic equipments for measurements of absorption and velocity in very wide frequency range from hundreds kHz to tens GHz. At the end there were shown several experimental examples of possible taking the advantage of the ultrasonic spectroscopy.
In the present paper, the authors discuss studies carried out for many years by numerous acoustics researchers, dealing particularly with two compounds: benzene and carbon disulphide. They are typical liquids in which acoustic Kneser-type relaxation occurs, caused by an irreversible vibrational-translational (VT) transition. Since magnitudes describing the relaxation process were diverse in many papers, we have undertaken an attempt to clarify these differences and to indicate how to avoid errors resulting from instrumental imperfections and the disregard of considerable measurement errors when investigating velocity dispersion in the hypersonic range.
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