In the present work the existence of a common intersection point for the isobars of internal pressure of some liqs. of interest as a function of temp. has been investigated, exptl. and theor. The regularity has been tested for molten alkali metals and some pure liqs. The common intersection point occurs at approx. 0.57-0.62 of the crit. temp. of these liqs. We have found that the linear isotherm regularity (LIR), Ihm-Song-Mason (ISM) and Peng-Robinson (PR) equations of state are able to predict the common internal pressure point. An important result obtained from this research is that we may get information about the magnitude of the sepn. at the min. of the av. effective potential well, rm, using the d. of the common intersection point, oi.

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