Improving the simplified-perturbed-hard-chain theory equation of state using a new non-attracting hard-sphere equation

In this research a new simple non-attracting hard-sphere equation is introd uced. The equation meets the ideal gas and close-packed limits and is in ac cordance with computer simulation data with reasonable accuracy. When this equation is used with the simplified-perturbed-hard-chain theory equation o f state, improvements on the calculation of vapour pressure and saturated l iquid density of pure compounds are observed. For 35 pure compounds of diff erent classes, the averages of absolute error are 3.31% and 4.20% for the c alculation of vapour pressure and saturated liquid density, respectively. T he respected errors for the original equation of state are 3.53% and 4.96%, respectively. Moreover, the use of the new hard-sphere equation in place o f the Carnahan-Starling equation in the simplified-perturbed-hard-chain the ory equation of state, does not have any appreciable effect on the predicti on of K factors in VLE calculations.