The viscosities of aqueous solutions of gelatin at different temperatures were carefully measured in a common glass-capillary Ubbelohde viscometer at dilute to extremely dilute concentrations. The adsorption effect that occurred in the viscosity measurements was theoretically analyzed and discussed. A theory based on Langmuir isotherms could adequately describe the existing data. Some structural information was obtained by the use of an iterative fitting procedure to treat the reduced viscosity data, which disclosed that individual gelatin chains underwent a coil-to-helix transition as the solution cooled from 40 to 15 degrees C. (c) 2006 Wiley Periodicals, Inc.