text: For pure elements or compounds, e.g. pure copper, pure water, etc. the liquidus and solidus are at the same temperature, and the term melting point may be used.
  There are also some mixtures which melt at a particular temperature, known as congruent melting. One example is eutectic mixture. In a eutectic system, there is particular mixing ratio where the solidus and liquidus temperatures coincide at a point known as the invariant point. At the invariant point, the mixture undergoes a eutectic reaction where both solids melt at the same temperature.