How can a mixed melting point confirm the identity of an unknown compound?

The melting point is not enough to definitely identify the compound because different compounds may have a similar melting point range. It all depends on the compounds. If you have a compound of acetanilide and flourene, the results will lead to similar melting points of 115 degrees Celsius and 116 degrees of Celsius. The ranges will be similar so it would be hard to definitely identify the compound.