Critical Point
| Also Known As | Critical state, liquid-vapour critical point, thermodynamic critical point |
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What is Critical Point?
The critical point of a substance is the temperature and pressure above which the distinction between liquid and vapour phases disappears, forming a supercritical fluid. At the critical point, the liquid and vapour phases have identical densities. Above the critical temperature (Tc), a gas cannot be liquefied by pressure alone. For water, Tc = 374°C and Pc = 218 atm.
Properties & Characteristics
Uses & Applications
Safety Information
Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.
Key Facts
Frequently Asked Questions
The critical point of a substance is the temperature and pressure above which the distinction between liquid and vapour phases disappears, forming a supercritical fluid. At the critical point, the liquid and vapour phases have identical densities. Above the critical temperature (Tc), a gas cannot be liquefied by pressure alone. For water, Tc = 374°C and Pc = 218 atm.
Critical point data is used in industrial design of distillation columns, supercritical extraction (CO₂: T_c = 31.1°C, P_c = 73.8 atm used in decaffeination, extraction of hops), supercritical fluid chromatography (SFC), and in chemical engineering equations of state.
Operating near the critical point requires high-pressure equipment rated for P_c. Supercritical CO₂ equipment must have pressure relief valves and be operated only by trained personnel. Sudden depressurisation of supercritical fluids can cause rapid cooling and dry ice formation (CO₂).