History of Sonochemistry
Ultrasonic research began in the twenties of the last century. During this time not only politics and culture where subjected to change in the science many new ideas were put into practice. The best known example is probably the quantum mechanics, the revolutionary physics of the microwaves, which until today determines our ideas about the structure of the atomic world. In 1927, however, a rather unknown chemist named Alfred L. Loomis published a study on the "physical and biological effects of high-frequency sound waves". In it, Loomis and his associate Wood reported for the first time that ultrasound bacteria can break up. In another work of the same year, Loomis and his colleague Richards described many fundamental phenomena that initiate ultrasound in solutions, solids, and pure fluids. For example, Loomis's investigations showed that ultrasound accelerates the dispersion of mercury, as well as the flocculation of silver chloride, the hydrolysis of dimethyl sulfate, and the reaction known as the "iodine clock". The degassing of liquids has also been described therein and the fact that ultrasound reduces the boiling points of liquids. After this pioneering work the interest in possible ultrasound applications also awoke to other researchers. Biologists were particularly concerned with the effect that the acoustic sound waves have on bacteria, viruses and other micro-organisms. Not only was it discovered that almost all bacteria can be easily killed with ultrasound, but also that cells can be disrupted, for example, in order to dissolve certain ingredients. Chemists, on the other hand, studied mainly the effects of ultrasound on inorganic chemical reactions, mostly in simple (so-called homogeneous) systems in aqueous solutions. At that time, the individual research groups, however, had very differently designed devices that varied widely in performance, frequency and intensity. However, since these factors can be particularly important for a specific chemical effect, there have been very different results in this early period of ultrasound research and it has been difficult to generalize them. In the fifties and sixties, the industry developed the first handy, powerful homogenizers. Gradually, more and more application possibilities emerged. This ranged from the use in plastic welding to material fatigue tests or the supporting effect in the crystallization of metal melts. The scientific interest in ultrasound research also grew with the accompanying production of high-performance and cost-effective devices. Especially in chemistry, there has been an ultrasound renaissance, and a large number of reactions have taken place which proceed faster and with greater yield under the catalytic effect of acoustic waves. In the meantime, one speaks of a special subject, the "SONOCHEMNISTRY", whose representatives have been meeting regularly since 1986 for their international symposium.
Brown, B. and Goodman, J.E.
High Intensity Ultrasonics - Industrial Applications
Synthesis with ultrasonic waves
Journal of chemical education, Vol.63, No. 5, 427; 1986
Kirk - Othmer:
Encyclopedia of chemical technology, Vol. 23, 462, 3.Edition; 1982
Mason, T.J. and J.P. Lorimer
Hemel Hempstead; Ellis Horwood Ltd; 1991
Suslick, Kenneth S.
Weinheim; VCH Verlagsgesellchaft; 1988
The chemical effects of Ultrasound
Scientific American, S. 62, Feb. 1989