Ultrasound research began in the 1920s. During this time, a lot was happening not only politically and culturally, but also in science, where many new ideas were put into practice. The best-known example is probably quantum mechanics, the revolutionary physics of the micro-world, which still determines our ideas about the structure of the atomic world. In 1927, however, a rather unknown chemist named Alfred L. Loomis also published a study on the "Physical and Biological Effects of High-Frequency Sound Waves". In it, Loomis and his colleague Wood reported for the first time that ultrasound can break up bacteria. In another paper from the same year, Loomis and his colleague Richards then described many fundamental phenomena that ultrasound initiates in solutions, solids and pure liquids. For example, Loomis' investigations showed that ultrasound accelerates the dispersion of mercury, as well as the flocculation of silver chloride, the hydrolysis of dimethyl sulphate and the reaction known as the "iodine clock'". It also described the degassing of liquids and the fact that ultrasound lowers the boiling points of liquids. After this pioneering work, interest in possible ultrasound applications also awoke among other researchers. Biologists were particularly interested in the effect that acoustic sound waves have on bacteria, viruses and other small organisms. Not only was it discovered that almost all bacteria can be easily killed with ultrasound, but also that it can be used to break down cells, for example to dissolve out certain substances. Chemists, on the other hand, mainly studied the effects of ultrasound on inorganic chemical reactions, mostly in simple (so-called homogeneous) systems in aqueous solutions. At that time, however, the individual research groups had very differently constructed devices, which often varied greatly in power, frequency and intensity. However, since these factors can be decisive for a specific chemical effect, there were often divergent results in these early days of ultrasound research and it was difficult to generalise. In the 1950s and 1960s, industry developed the first handy, powerful homogenisers. Gradually, more and more possible applications emerged. These ranged from use in plastic welding to material fatigue tests or the supporting effect in the crystallisation of molten metals. With the accompanying production of powerful and inexpensive devices, scientific interest in ultrasound research also grew again. Especially in chemistry, there was a renaissance of ultrasound and a multitude of reactions were found that run faster and with greater yield under the catalytic effect of acoustic waves. In the meantime, there is already talk of a separate field, "SONOCHEMIE", whose representatives have been meeting regularly for their international symposium since 1986.
Brown, B. and Goodman, J.E.
High Intensity Ultrasonics - Industrial Applications
Organic chemistry with ultrasound
Weinheim; VCH Publishing Company; 1983
Synthesis with ultrasonic waves
Journal of chemical education, Vol.63, No. 5, 427; 1986
Kirk - Othmer:
Encyclopedia of chemical technology, Vol. 23, 462, 3rd Edition; 1982
Physics and technology of ultrasound
Stuttgart, Hirzel-Verlag; 1988
Ley, Steven V. and Caroline M.R. Low
Ultrasound in Synthesis
Berlin, Heidelberg, New York; Springer-Verlag ; 1989
Mason, T.J. and J.P. Lorimer
Hemel Hempstead; Ellis Horwood Ltd; 1991
Millner, Dr Rudolf
Ultrasound Technology: Fundamentals and Applications.
Suslick, Kenneth S.
Weinheim; VCH Verlagsgesellchaft; 1988
The chemical effects of Ultrasound
Scientific American, p. 62, Feb. 1989