Raoultian and Henrian standard states

The activity of Ni in molten Fe-Ni at 1850 K using the Henrian standard state is also given in the figure (ordinate given on the right-hand y-axis). 

If an arbitrary standard state is marked with, a formal definition of a Raoultian standard state for component A of a solution is 

It follows that the activity coefficient with this standard state  

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In the following, the Raoultian and Henrian standard states will be presented. These two are the far most frequent standard states applied in solution thermodynamics. Before discussing these standard states we need to consider Raoult s and Henry s laws, on which the Raoultian and Henrian standard states are based, in some detail. 

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