Critical opalescence

Critical opalescence is a phenomenon which arises in the region of a continuous, or second-order, phase transition. Originally reported by Charles Cagniard de la Tour in 1823 in mixtures of alcohol and water, its importance was recognised by Thomas Andrews in 1869 following his experiments on the liquid-gas transition in carbon dioxide; many other examples have been discovered since. In 1908 the Polish physicist Marian Smoluchowski became the first to ascribe the phenomenon of critical opalescence to large density fluctuations. In 1910 Albert Einstein showed that the link between critical opalescence and Rayleigh scattering is quantitative.