Experience shows, the change of the external pressure on the solids effect on the melting point of this substance. In those cases, when the volume of the substance during melting increases, the increase in external pressure, which complicates the process of melting, leads to raising the temperature of the melting. If the volume of the substance during melting is reduced, the increase in external pressure leads to a decrease in the melting point of this substance, as increased pressure in this case helps the melting process. Note, only a very large increase in pressure noticeably changes the melting point of the substance. For example, to lower the melting point of ice at 1 Calvin, the pressure needs to improve on 130 atmospheres.

The melting point of the substance at atmospheric pressure is called melting point of a substance.

It turns out, what is the specific heat of melting ‘It also depends on the pressure. At high external pressures the substance in the enlargement process should make visible the work against the forces of external pressure. Therefore, those substances, which upon melting expands, specific heat of melting by increasing the external pressure increases, and ice, bismuth and gallium — decreases. For example, if under normal pressure for mercury λ_Hg=11,5*10³ J/kg and bismuth λ_Bi=54,5*10³ J/kg, when the pressure 12*10³ ATM λ_Hg=13,2*10³ J/kg and λ_Bi=38,1*10³ J/kg.