Historical development of sonochemistry

Ultrasound research began in the 1920s. During this time, a great deal was happening not only politically and culturally - many new ideas were also put into practice in science. The best-known example is probably quantum mechanics, the revolutionary physics of the microworld, which still determines our ideas about the structure of the atomic world today. 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. Following this pioneering work, other researchers also became interested in possible ultrasound applications. 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 open cells, for example to extract 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 terms of power, frequency and intensity. However, as 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, the 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 cost-effective devices, scientific interest in ultrasound research grew again. In chemistry in particular, there was a veritable ultrasound renaissance and a large number of reactions were discovered that take place faster and with greater yield under the catalytic effect of acoustic waves. In the meantime, it has become a specialised field in its own right, "SONOCHEMISTRY", whose representatives have been meeting regularly for their international symposium since 1986.

Further reading:

Brown, B. and Goodman, J.E.

High Intensity Ultrasonics - Industrial Applications

Boudjouk, P.

Organic chemistry with ultrasound

Weinheim; VCH Publishing Company; 1983

Boudjouk, P.

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

Kuttruff, Heinrich

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

Sonochemistry

Hemel Hempstead; Ellis Horwood Ltd; 1991

Millner, Dr Rudolf

Ultrasound Technology: Fundamentals and Applications.

Weinheim, Physik-Verlag;1987

Suslick, Kenneth S.

Ultrasound

Weinheim; VCH Verlagsgesellchaft; 1988

Suslick, K.S.

The chemical effects of Ultrasound

Scientific American, p. 62, Feb. 1989

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