PRESSURE OF SATURATED STEAMS AS INDICATOR OF STRUCTURAL CHANGES IS IN LIQUIDS
DOI:
https://doi.org/10.20535/2218-93002322018144955Keywords:
molecular liquids, structurizing, structure-dependent properties, mathematical functions, structural analysisAbstract
The results show that the pressure of saturated vapors of water and other molecular liquids can indeed be affected by structural changes in the volume and even on the surface. On the basis of supposition that homogeneously structured liquids have permanent energy of activating, two functions are shown out: "cubic" - for pressure of saturated steams (∛Р=f (T)) and "square" - for a surface-tension waters (√σ= f (T)) that can keep straightforwardness in the termobaric terms of existence of corresponding structures. Calculations have showed that the first function well described 4-phase changes of water structure at heating to 374 °C and it is suitable for the analysis of in other molecular liquids. The second function confirms homogeneity of structures of interface surface in waters of I and II types.
For liquids with weak intermolecular interaction, only two types of volume structuring were found — before and after the boiling point. In this case, high-temperature structures are always homogeneous, and low-temperature structures can be homogeneous (C2H6, СН3Cl) or non-uniform (СН3ОН, CCl4). It is noted that the existence of high-temperature structures for the liquids under consideration is not due to temperature, but to high pressures, which have to be used to preserve these substances in a liquid state.
It is well-proven by means of "cubic" function that in the concentrated solutions of Н2SO4 below 40 °С it is possible to find out the presence of hydrates of H2SO4 ⸱6,5Н2О, H2SO4 ⸱4Н2О, H2SO4 ⸱3Н2О і H2SO4 ⸱2Н2О. The character of structurizing of water in salt solutions to 100 °С, as a rule, remains immutable. But in saturated solutions of KNO3 over 50 °С there is formation of some homogeneous structure of water. The results show that salts can change the structure of water only in cases of high concentrations and special properties of their ions.
Using the "cubic" function of the saturated vapor pressure can be a new method for structural analysis of liquids. This method can be especially useful in the study of systems with H-bonds, as well as in the case of salt solutions that can form crystalline hydrates.
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