Estimate the $$ for $1-$butene vapor at $473\mathrm{.}15K$ and $70$ bar. Available data: $Tc=420K,Pc=40\mathrm{.}43$ bar and $=0\mathrm{.}191.$

Working equation:

$ln=\frac{Pr}{Tr}(B_o+B_1)$

$B_o=0\mathrm{.}083-\frac{0\mathrm{.}422}{T{r}^{1\mathrm{.}6}}$

$B_1=0\mathrm{.}139-\frac{0\mathrm{.}172}{T{r}^{4\mathrm{.}2}}$