Kamerlingh Onnes constructs Gibbs surfaces assuming continuity of states

Abstract

Driven by the idea of continuity of states, Kamerlingh Onnes built a number of Gibbs energy–entropy–volume surfaces early in the 20th century. He devised an original method to construct such surfaces based on the van der Waals equation, and discovered that the surfaces have a sharp ridge running close to the liquid branch of the coexistence curve. He also built several surfaces for water and for carbon dioxide, including their solid phases. He made a major effort to represent faithfully the known data for these substances, including Tammann's new experimental high-pressure data. He proposed that the solid phases be represented by ridges similar to the liquid ridge, the ridges being caused by additional loops in the equation of state. This led him to the controversial concept of solid–liquid criticality, which is illustrated by several of his models.