  Finite systems may undergo first or second order phase transitions under not
isovolumetric but isobaric condition. The `analyticity' of a finite-system
partition function has been argued to imply universal values for isobaric
critical exponents, $\alpha_{{\scriptscriptstyle{P}}}$,
$\beta_{{\scriptscriptstyle{P}}}$ and $\gamma_{{\scriptscriptstyle{P}}}$. Here
we test this prediction by analyzing NIST REFPROP data for twenty major
molecules, including $\mathrm{H_{2}O, CO_{2}, O_{2}}$, etc. We report they are
consistent with the prediction for temperature range, $10^{-5}
<|T/T_{c}-1|<10^{-3}$. For each molecule, there appears to exist a
characteristic natural number, $n=2,3,4,5,6$, which determines all the critical
exponents for $T<T_{c}$ as
$\alpha_{{\scriptscriptstyle{P}}}=\gamma_{{\scriptscriptstyle{P}}}=\frac{n}{n+1}$
and $\beta_{{\scriptscriptstyle{P}}}=\delta^{-1}=\frac{1}{n+1}$. For the
opposite $T>T_{c}$, all the fluids seem to indicate the universal value of
${n=2}$.
