Heat Capacity Ratios for Real Gases

For many calculations it is required to know the ratio of Cp/C, for a gaseous compound. The well-known expression Cp-C = R (where R is the universal gas constant) holds good only for gases under ideal conditions. When working with situations involving real gases, the relationship between Cp and C, is given as  

= Critical pressure Tj = Critical temperature in absolute units For Cp and C, in metric units, the value for R is 1.987 cal (gm-raole)-°K 

---