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1953
Sharpness of critical point: Optical density measurements of Lorentzen
When mapping out the curves experimentally for equations of
state, it turns out that the shape of the isotherms can be
remarkably sensitive to variations in density. Lorentzen
arranged a vertical glass tube filled with CO2 at extremely
stable temperatures so that slits at each end would define
a cylindrical lens whose focal length depended on the fluid
density. Near the critical point tiny differences in
height could lead to large discrepancies in density. That
most previous tests of equations of state did not take this
density inhomogeneity into account meant that coexistence
curves had been unduly flattened, implying that the
critical transition was more gradual than it actually was.
Primary:
H. L. Lorentzen, "Studies of critical phenomena in carbon
dioxide contained in vertical tubes," Acta Chem. Scand. 7
(1953): 1335-1346.
Secondary:
Brush 1983, 249
Heller 1967, 735
--Karl Hall
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