Historical Development

In 1556, an extraordinary book entitled De Re Metallica, Libri XII appeared in Basel. The author was a German physician, naturalist and mineralogist, calling himself Georgius Agricola (originally called Georg Bauer), living in Jachymov, Bohemia, from 1494 to 1555. Agricola described, in a fascinating manner, the contemporary advances in metals and

1This article does not deal with the important particle separation techniques of filtration, flotation and the use of membranes which are dealt with elsewhere in the Encyclopedia.

minerals recovery and gave us a very detailed report on the sophisticated technologies of his epoch. This late medieval period saw a true expansion of science and technology in Europe. Winston Churchill once said:'... from this date, 1492, a new era in the history of mankind takes its beginning'. As many metal recovery processes used at that time were based on various separations of particulate matter and De Re Metallica, Libri XII seems to be the first printed review of separation technologies, it is fitting to acknowledge Agricola's publication priority in this field and to consider his book as the beginning of a modern scientific approach to particle size separations.

The reproduction of a rendering in Figure 1 taken from Agricola's book shows a surprisingly sophisticated device for gold (and other metals) recovery by 'panning' or 'sluicing' which used gravity and

Figure 1 Mediaeval device for the recovery of gold particles and minerals from sand, clay, and soil blends by combining the sedimentation and quasi-horizontal stream of water, accompanied by vigorous manual stirring of the mud cake. (Bottom) The author of the book De Re Metallica, LibriXII, Georgius Agricola.

Figure 1 Mediaeval device for the recovery of gold particles and minerals from sand, clay, and soil blends by combining the sedimentation and quasi-horizontal stream of water, accompanied by vigorous manual stirring of the mud cake. (Bottom) The author of the book De Re Metallica, LibriXII, Georgius Agricola.

a stream of running water to separate gold particles from other solid material (soil, clay, sand, etc.). Astonishingly, this technology dates back to at least 4000 to 5000 bc.

Original scientific discoveries, outstanding inventions and innovations in technology representing the important achievements at a given moment reflect continuity of imagination throughout the long history of civilization. When looking for the background and genesis of modern and powerful separation methodologies and technologies, very often natural analogies can be found at a macroscopic level. An image of a river meandering through the countryside and removing soil, clay, sand, and stones from a river bank, carrying them off in the stream, and depositing them later at other places, is one such example. On the other hand, although ancient technologies can have essentially the same goal (separation), in a manner similar to that in which 'cat's cradle' is equivalent to a sophisticated electronic computer game, the intellectual progress is evident.

Dry and wet sieving, sedimentation, and filtration are probably the most ancient, intelligently applied, separation processes on which the foundations of modern separation science stand. These processes were originally exploited for the separations of disintegrated matter whose average 'particle' size was somewhere between millimetre and centimetre fractions, sometimes even bigger. Slowly, the need to separate smaller and smaller particle size material became apparent. The old-fashioned but transformed methods still afforded positive answers to questions which appeared in relation to the new separation problems. However, these transformations gave rise to newer methods which, together with the discovery and invention of completely new principles, symbolize the state of the art of particle separation.

Solar Panel Basics

Solar Panel Basics

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