fractional fusion
THE fractional fusion is used to separate solids whose points from Fusion They are very different. How can we separate a mixture of solids like iron, lead and tin?
If we have two solids with different melting points and we know what the fusion point from each of the substances, it's relatively easy to separate them: we can heat them up and make one of them drain. Tin melts at 231°C; lead, at 327°C; iron, at 1536 °C. We can melt (melt) tin first, then lead, and lastly iron. Each element, when melting, is separated from the others.
This process is also used to separate sulfur and sand in the process of obtaining sulfur from underground deposits. This process is called Frasch.
There are mixtures that cannot be separated by fractional melting, because of the way they behave during the melting or boiling process. Let's see why:
eutectic mixture: is the type of Mix which behaves like a pure substance during fusion, therefore, it cannot be separated by fractional fusion as it has a constant melting point. The separation of components from eutectic mixtures is done by distillation. Example: mixture of tin and bismuth.
azeotropic mixture: it behaves like a pure substance during boiling, fractional fusion is used to separate its components, as we have just seen.
Fractional Solidification
It consists of heating the mixture until the component with the lowest melting point (M.P.) melts.
Have you noticed how important it is to know the physical properties of a substance? Boiling and melting points are important for separating compounds. The solidification point is also useful for separating the components of a mixture.
Fractional solidification can, for example, be used to separate paraffin from other petroleum residues. In this case, the mixture is cooled down to the paraffin solidification point. Thus, hardened, the paraffin is removed from the mixture.
By Líria Alves
Graduated in Chemistry
Source: Brazil School - https://brasilescola.uol.com.br/quimica/fusao-fracionada-solidificacao-fracionada-1.htm