Toop’s equation

Here, the solute S is in dilute solution, and tire equation can be used across the enthe composition range of tire A-B binary solvent, when Aa + Ab is close to one. When the concentration of the dilute solute is increased, the more concentrated solution can be calculated from Toop s equation (1965) in the form... 

Both the Muggianu and Kohler equations can be considered symmetrical as they treat the components in the same way and do not differentiate between them. This is true for another method suggested by Colinet (1967) which is derived differently than either the Kohler or Muggianu equations but which can be reduced to the Muggianu equation (Hillert 1980). Toop s equation (1965) is essentially different in that it considers one of the binary systems does not behave in the same way as the others and the extrapolation is based essentially on two of the binaries having identical mole-fraction products with the mole-fiaction products of the third being different. For a sub-regular solution Toop s equation breaks down to (Hillert 1980)... 

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