Surface Tensions of Alkyl Lactates with n-Alkanols or Branched Alkanols

The surface behavior of 18 binary mixtures at T = 298.15 K and at atmospheric pressure (p = 0.1 MPa) was measured with a drop volume tensiometer. These mixtures are formed by alkyl lactates (methyl lactate and ethyl lactate) and alcohols (n-alkanols from methanol to 1-hexanol and isomeric butanols). Surface tension deviations for all these systems were calculated and correlated with the mole fraction using the Myers–Scott equation. For the mixtures alkyl lactate with methanol, the surface tension deviations are positive. With regard to the mixtures containing ethanol, the surface tension deviation is positive for methyl lactate and slightly negative in the lactate-poor region for ethyl lactate. For the rest of the mixtures, the surface tension deviations are negative. A molecular interpretation of the different behaviors observed was proposed.