reference electrode (3). The ionized calcium concentration of sequential retentates prepared by ultrafiltration of a human control serum increased with increasing protein concentration in a way consistent with Donnan theory (4, 5) when the analyzers’ standard reference-electrode liquid junctionswere used; however, the ionized calcium in the same retentates declined slightly with increasing prot...

The streaming potentials of two different nanofiltration membranes were studied with several electrolyte solutions to investigate the influence of salt type and concentration on the zeta potential and kinetic surface charge density of the membranes. The zeta potentials decreased with increasing salt concentration, whereas the kinetic surface charge densities increased. The kinetic surface charg...

The classical Gibbs-Donnan equilibrium describes excess osmotic pressure associated with confined colloidal charges embedded in an electrolyte solution. In this work, we extend this approach to describe the influence of multivalent ion binding on the equilibrium force acting on a charged rod translocating between two compartments, thereby mimicking ionic effects on force balance during in vitro...

Although Frederick George Donnan (Fig. 1) grew up in Northern Ireland, actually he was born in Columbo, Ceylon (now Sri Lanka), on September 5, 1870 (1). He lost the sight of his left eye at the age of nine but did not allow this accident to handicap him. As a schoolboy, his main interest was in mathematics and physical science. He attended the Belfast Royal Academy from 1880 to 1889; and altho...

An answer has been given by Hitchcock 1 to a recent criticism by myself 2 of an argument vigorously exploited by Loeb in favor of his theory of colloidal behavior. Hitchcock suggests that this criticism rests upon a misunderstanding, but he admits the validity of my main contentions, and I am happy to note that Loeb has taken heed of them in two recent papers. I have no quarrel with many of the...