Sentence:  Whereas the usual organic surface-active agent is strongly sorbed at oil-water interfaces , the highly charged ions are most strongly sorbed at interfaces between <WSD>water</WSD> and insoluble materials exhibiting an ionic structure ( see Table 26 - 2 on p. 1678 ) . 
Meaning of the word marked with <WSD> tags:  binary compound that occurs at room temperature as a clear colorless odorless tasteless liquid; freezes into ice below 0 degrees centigrade and boils above 100 degrees centigrade; widely used as a solvent