Thomas Andrews (1813-1885) was an Irish scientist known primarily for his contributions to thermodynamics and physical chemistry. He is best remembered for his work on the critical point and the behavior of gases and liquids. One of his most significant achievements was the formulation of the concept of the "critical state" of substances, which describes the conditions at which the distinctions between gas and liquid phases disappear.
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Thomas Andrews measured the pressure-volume behaviour of carbon dioxide around its liquid-gas critical region. Coupled capillaries and controlled water jackets connected pressure changes with temperature and the visible disappearance of a phase boundary.
The observations show how a liquid can be connected continuously with a gas by a path around the critical point. They distinguish a phase-boundary crossing from every possible change between liquid-like and gas-like densities.[ref]
The Bakerian Lecture: On the Continuity of the Gaseous and Liquid States of Matter by Thomas Andrews. 1869, pages 576–580 and Plate LXIII
A chemist.[ref]
https://www.qub.ac.uk/News/Allnews/2024/Queens-University-Belfast-pioneer-Thomas-Andrews.html. Independent biographical identity and professional specialization
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Portrait of Thomas Andrews
. Richard Hooke (1820–1908), painting; reproduction photographer not identified. No free license verified; external biographical illustration under the user-authorized fair-usage policy, via Wikimedia Commons. Source._-_Professor_Thomas_Andrews_(1813%E2%80%931885)_-_QUB_35_-_Queen%27s_University_Belfast.jpg){kind=link}