Crystallization means you allow the liquid to cool at a rate slow enough to form crystals (ie, produce stable, long range order of atoms/molecules). Solidification can produce a crystal or not. When you cool a liquid metal you obtain a solid that usually is crystalline.

What is Oiling Out in Crystallization? Oiling out in crystallization is a process in which supersaturation causes the initially dissolved compound to separate from solution by creating a secondary liquid phase (emulsion) (image 1a) instead of a solid, crystalline phase (suspension) (image 1c).

Recrystallization is the most important method of purifying nonvolatile organic solids. Recrystallization involves dissolving the material to be purified (the solute) in an appropriate hot solvent. As the solvent cools, the solution becomes saturated with the solute and the solute crystallizes out (reforms a solid).

tungsten

Impurities, even when present in small amounts, usually lower the melting point and broaden the melting point range. A wide melting point range (more than 5°C) usually indicates that the substance is impure; a narrow melting point range (O. 5-2°C) usually indicates that the substance is fairly pure.

Melting points are often used to characterize organic and inorganic crystalline compounds and to ascertain their purity. Pure substances melt at a sharp, highly-defined temperature (very small temperature range of 0.5 – 1 °C) whereas impure, contaminated substances generally exhibit a large melting interval.

When an impurity is added its freezing point is lowered i.e. its freezing point decreases. The depression in freezing point increases with the increase in concentration of the solute because on adding the solute the vapour pressure of solution becomes lower than that of pure solvent.