INTERFACIAL ACTIVITY OF DECYL PYRIDINEMONOCARBOXYLATES

Interfacial activity of decyl pyridinemonocarboxylates with or without the presence of decanol was studied in systems containing an excess o f modifier and a constant ratio of extractant to modifier used in comp arable amounts. The importance of appropriate procedures for reprocess ing the interfacial tension data has been demonstrated for the estimat ion of the absolute and relative interfacial concentrations of extract ant molecules at the interface. Decyl isonicotiniate has the highest i nterfacial activity when compared to that of decyl nicotiniate and dec yl picoliniate. When alcohol is used in a large excess then the interf ace is mainly occupied by its molecules. In systems containing compara ble amounts of decyl picoliniate and decanol, the co-adsorption of the se two compounds occurs with mole fractions at the interface close to 0.4 and 0.6 for decyl picoliniate and decanol, respectively. It should , however, be pointed out that the determination of the mole fractions of these two compounds at the interface was possible only in a very l imited region of concentrations corresponding to a domain of interfaci al tension ranging from 26 to 29 mN m(-1).