What is Andrews Isotherm
Andrew isotherm is the plot of pressure verses volume(P-V-plot) at different temperature for carbon dioxide. Each of the plots are an isotherm however it is known as Andrew isotherm because the critical phenomena and P-V-isotherm is noticed on CO2 gas molecules by Andrews in 1861.
In his studies over CO2 gas, he explained that when, temperature is 13.10C ,at low pressure ,the CO2 exists as a gas at the point A in graph, while when the pressure is increased the volume decreases along the curve shown AB, and at the point B the liquefaction starts.
At the point C, liquefaction is complete and now the increase in pressure has very little effect on volume. Hence, the straight CD curve is obtained which becomes more and more smaller at horizontal position when the temperature is increased and at 30.98 0C , the curve is reduced at point P.
So, above the temperature 30.980C the gas can not liquefy and this is called as critical temperature(Tc) and the corresponding pressure is its critical pressure(Pc) and the isotherm at this temperature is called as critical isotherm.
The detailed graph is given as:
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In his studies over CO2 gas, he explained that when, temperature is 13.10C ,at low pressure ,the CO2 exists as a gas at the point A in graph, while when the pressure is increased the volume decreases along the curve shown AB, and at the point B the liquefaction starts.
At the point C, liquefaction is complete and now the increase in pressure has very little effect on volume. Hence, the straight CD curve is obtained which becomes more and more smaller at horizontal position when the temperature is increased and at 30.98 0C , the curve is reduced at point P.
So, above the temperature 30.980C the gas can not liquefy and this is called as critical temperature(Tc) and the corresponding pressure is its critical pressure(Pc) and the isotherm at this temperature is called as critical isotherm.
The detailed graph is given as: