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 ${n=2}$.
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