The relative volatility $({}_{12})$ for the system consisting of carbon

sulphide $(1)$ and acetone $(2)$ at $35\mathrm{.}17C$ is given by the following

empirical equation:

${}_{12}=\frac{1+7\mathrm{.}0783x_2-2\mathrm{.}4044x_2^2}{1+1\mathrm{.}4856x_1+2\mathrm{.}5819x_1^2}$

If $P_1^{\text{s}\text{a}\text{t}}=0\mathrm{.}691$ bar and $P_2^{\text{s}\text{a}\text{t}}=0\mathrm{.}498$ bar, get estimates for:

a$.$ The activity coefficients at infinite dilution.

b$.$ Composition and pressure at the azeotrope.