The entropy of mixing and assimilation: An information-theoretical perspective

It is claimed that the quantity -k Sigma x(i) ln x(i), the so-called "entropy of mixing," has nothing to do with the mixing process, and that, contrary to the accepted view, mixing,is not an irreversible process. Instead, the process of deassimilation is introduced, and it is shown that it is an inherently irreversible process. The information-theoretical perspective of these statements is discussed for classical and quantum-mechanical systems of noninteracting particles. (C) 2006 American Association of Physics Teachers.