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critical volume[′krid·ə·kəl ′väl·yəm]
the specific volume of a substance (or mixture of substances) in its critical state. The specific volumes of the liquid and gaseous phases in the critical state become equal. This specific critical volume corresponds to a density approximately three times lower than the density of the substance in the solid state. (For values of the critical volume Vc of a number of substances, see .)