How can you choose that right technique to separate the solid?

-Here is an Example. A mixture has X and Y. X is a liquid at room temperature [Melting point at 5, Boiling point at 60] and Y is a solid at room temperature [Melting point at 745 and boiling point at 1218] -Y has completely dissolved in X -To get X, You will have to Distil it. Since its a liquid, and the boiling points are far apart. Distilling it will give you a Pure sample of X -To get Y, you should use Crystallisation. Its a soluble solid. [You could use the same technique as X, but there could be traces of X still there. This is just a better and reliable Technique]