AbstractsChemistry

In 1822 Cagniard de la Tour published the observation (15) that the meniscus separating the liquid from the gaseous phase in a closed glass “bomb” containing the two phases suddenly disappeared when the bomb was heated past a certain temperature. This phenomenon was systematically investigated by Andrews with carbon dioxide in 1869 (3) and his results, extended theoretically by van der Waals shortly afterwards, form the basis of the well known Andrews-van der Waals theory of the continuity of the liquid and gaseous state and of the concept of a -uniquely defined critical point (87). The far reaching implications of a continuous transition from the gaseous state, whose properties are easily interpretable in molecular terms, to the liquid state which was previously considered a separate and distinct state of matter with its own set of characteristic properties, led investigators thenceforth to test different aspects of the consequences of the theory. In short, the experimental question presented by the theory is: Do the properties of the liquid and of the gaseous phase, in fact, approach each other continuously at equal critical concentration and do they become identical at the critical point, or do the two phases retain characteristic properties even when visually indistinguishable? [...]