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Supercritical Carbon Dioxide

The critical point for a chemical is defined by the maximum temperature (critical temperature) at which a gaseous substance can be liquefied and by the pressure (critical pressure) needed to do this.
A gaseous substance below the critical temperature is called a vapour while one above is either a gas or supercritical fluid depending on the pressure. The critical point is characterised by a liquid like density and a gaseous like diffusion and viscosity. Physical properties of carbon dioxide can be found here. Small changes in temperature and pressure produce significant changes in density and solvent power. An example of this is naphthalene which is practically insoluble in low pressure carbon dioxide. At 100 bar the solubility is 10 g/L and at 200 bar it is 50 g/L.