This function passes through a minimum at xB = 0.5, at which point, l'Hopital's rule shows that r = 2. No mathematical solutions exist for r < 2, which physically means that the system is a single phase solution for all compositions. For r > 2, the same value of r is obtained for xB and 1 - xB.
To convert Eq (8.19) to the equation for the phase diagram (i.e., T Vs xB), the maximum r = 2 is equivalent to a unique temperature T* through Eq (8.18):
T* is called the critical solution temperature. It is a property of the A-B binary system that reflects its nonideal behavior, as represented in the regular solution approximation.
With the help of Eqs (8.18) and (8.20), Eq (8.19) becomes:
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Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.