Question

What is meant by mixed melting point determination ?

Answer 1

When there is an impurity, the melting point of substance shows a depression in its melting point. This can be used to identify unknown substance. Melting point of compound is an indicator of its purity. The sharper the melting point, more pure the compound. In mixed melting point determination we find the unknown from a group of references compound.

First melting point of unknown is determined

Reference compounds having melting point in the same range as that of unknown is selected.

These compounds are added to the unknown separately and melting point of each mixture is measured.

Only in those mixture which having the same substance as the reference show no depression in melting point while mixture of two different substance show a depression in melting point. Hence we can identify the unknown. This method is called mixed melting point determination