Liquid range of a substance is possible range of temperature where liquid is allowed to exist. The value of its liquid range is obtained by subtracting melting point from its boiling point. If boiling point is higher than its melting point, liquid range is said to be positive; if boiling point is lower than its melting point, liquid range is negative, meaning that liquid is not possible to form unless pressure applied on the substance is raised.
The most familiar substance is water, whose liquid range is +100°C (+180°F), since the melting point is 0°C (32°F) and boiling point 100°C (212°F). The substance with greatest positive liquid range is faradium, whose value is +4903°C (+8826°F); substance with greatest negative liquid range is carbon, whose value is −663°C (−1193°F).