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 water and insoluble materials exhibiting an ionic structure ( see Table 26 - 2 on <WSD>p.</WSD> 1678 ) . 
Meaning of the word marked with <WSD> tags:  one side of one leaf (of a book or magazine or newspaper or letter etc.) or the written or pictorial matter it contains