In my textbook, it says that impurities lower the melting point and increase the boiling point. But is this only true if the boiling point of the impurity is greater than the boiling point of the solvent, and the melting point is greater than of the solvent too? So essentially, if greater bp impurity, boiling point of solution will be increased. if lower bp impurity then the boiling point of solution is decreased. If greater mp impurity, melting point is lowered. if higher melting point impurity then the melting point of the solution will be decreased. then what about alloys? so if i have two metals i want the alloy to have a low melting point, then i put a impurity that has a higher melting point so that the alloy will have a lower melting point? Must the impurity have a smaller percentage in the alloy or the effect will be otherwise where the impurity have a lower melting point which will in turn increase the overal melting point of the alloy?