Activity Coefficient of a Solute

Abstract

The chapter mentions the relations which on one hand link the activity and the concentration of the solute in the conditions in which an osmotic pressure is developing and, on the other one, when the solution is maintained at constant temperature and pressure. In other words, the activity coefficients are focused. It is known that the activity coefficients of the imperfect gases can be theoretically related to the virial coefficients (changing with the nature of the gas) which are purely experimental parameters. For very weak density numbers of the gases, this result is very interesting since it permits, at least in principle, to forecast the changes in the value of the activity coefficient and therefore in the changes of the activity when the density number vary, while, however, keeping a weak value.

Given the fact that the preceding theories, devoted to the osmotic pressure and to the solutions at constant pressure and temperatures, are very close to that applied to the real gases, it is not surprising that it is possible to theoretically relate the activity coefficients of the nonelectrolyte solutes to some experimental parameters. The reasonings involve the introduction of a new kind of activity applying to the osmotic equilibrium. The chapter mentions these relations and their setting up.