Surface potential and film pressure measurements in seawater systems1

Abstract

Surface potential (ΔV s ) and film pressure (γ f ) measurements of monolayers of standard compounds spread on organic carbon‐free seawater were compared to ΔV s and γ f values for natural films. The results suggest that natural seawater films most resemble films composed of proteins, polysaccharides, humic‐type material, and waxes. They contain relatively small amounts of free fatty acids, free fatty alcohols, or triglycerides, but the presence of relatively small amounts of these can strongly affect the resultant surface potential and film pressure of multicomponent films. Films formed very rapidly initially and formation rates decreased with time. Nevertheless, the potential for generating new films in 72‐liter natural seawater samples did not markedly decrease with time. Surface films derived from marine phytoplankton cultures had ΔV s and γ f properties similar to those of naturally occurring sea‐surface films. Cultures of marine bacteria contributed much less surface‐active material for film formation than did those of phytoplankton.