TABLE OF CONTENTS It is important to know the surface tension value and be able to predict it on the basis of the chemical structure of the substance is important, because many individual properties of liquids and solids, as well as miscibility and solubility of them in each other, depend on the surface tension of liquids and surface energy of solids. Among existing methods of calculation of surface tension, the most wide-spread is the additive scheme based on summing up of parachors which characterize the contribution of separate atoms to surface tension. The calculation is performed by the formula
| (XIII.1) |  |
where P is the total parachor of the molecule (or the repeat unit of the polymer); P i are parachors typical of every atom.
Values of atomic parachors P i, as well as constants which characterize contribution of various types of bonds (double, triple) and cycles (three-component, four-component, etc.) to the general parachor of the substance, are indicated in Table 45.
| Atom | P i | Constants | P j |
|---|---|---|---|
| C | 4.8 | Double bond | 23.2 |
| H | 17.1 | ||
| O | 20.0 | Triple bond | 46.4 |
| O 2 [*] | 60.0 | ||
| N | 12.5 | Three-component cycle | 16.7 |
| S | 48.2 | Four-component cycle | 11.6 |
| F | 27.5 | ||
| Cl | 54.3 | Five-component cycle | 8.5 |
| Br | 68.0 | ||
| I | 91.0 | Six-component cycle | 6.1 |
| [*]For two oxygen atoms participating in the ester |
Formula (XIII.1) enables the value
