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Engraving of Thomas Andrews (1813-85), Irish physical chemist. Andrews trained in medicine, graduating in 1835. From 1845 he taught chemistry in Belfast, a professorship he held for 34 years. Andrews made a study of the liqufaction of gases by pressure. It was known that some 'permanent' gases could not be liquefied at room temperature. Andrews studied the properties of carbon dioxide, and found that although it could be made liquid at room temperature, above 31 Celsius no amount of pressure could achieve this. This temperature he called the critical point. This work led to all of the so-called permanent gases being liquefied by applying a suitable reduction in temperature.
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