Electrokinetic Aspects of Surface Chemistry

It was shown by Loeb (1) that an approximate correspondence exists between the isoelectric points of gelatin or of egg albumin when in solution or adsorbed on the surfaces of microscopic particles. It remained for Abramson (2) to demonstrate a quantitative agreement between his own results for the electric mobility of serum albumin adsorbed on quartz surfaces and measured by the microscopic method of electrophoresis and the data of Tiselius (3) for solutions of freely dispersed serum albumin in U-tubes. Approximate agreement between the electric mobilities of adsorbed and dissolved egg albumin was also obtained but, in this case, it was noticed by Abramson that the isoelectric point of egg albumin is slightly shifted incidental to its adsorption. A recent reinvestigation of the electrokinetic properties of adsorbed egg albumin by Smith (4) and Moyer (5) has demonstrated that this divergence between the behavior of adsorbed and dissolved egg albumin is greater than had been originally indicated, the shift in isoelectric point being about 0.3 pH unit upward on the pH scale. Moyer also found that the shape of the electric mobility-pH curve of the adsorbed protein remains very nearly the same as in the dissolved state (5), except for a slight change in slope on the acid side. This was found true for egg albumin adsorbed on particles of quartz, glass, carbon, collodion, and mineral oil. Other, more polar surfaces, such as SiOL and A&OS, produced additional changes in slope from that obtained with the dissolved