ABSTRACT
The magnitude of surface tension change will depend on the concentration and the solute added. In some cases, the surface tension (γ) of the solution (such as NaCl) increases. The change in γ may be small (per mole added) (as in the case of inorganic salts) or large (as in the case of such molecules as ethanol or other soap-like molecules) with the addition of solute (equal gram per liter):
Inorganic salt: Minor change (increase) in γ Ethanol or similar: Small change (decrease) in γ Soap or similar: Large change (decrease) in γ
The following are typical surface tension data of different solutions:
This shows that, to reduce the value of γ of water from 72 to 30 mN/m, one would need to add 0.005 moles of sodium dodecyl sulfate (SDS) or 40% ethanol. Of course,
these two solutions cannot be used for the same application based on their similar magnitudes of γ.
