Surface Tension of Egg Albumin Solutions.

Abstract

Although it is generally believed that egg albumin is a capillarilly active substance, contradictory statements are often found in literature. According to Clark and Mann 1 egg albumin increases the surface tension of water in very dilute solutions but lowers it in more concentrated solutions. It is impossible to draw any conclusion from the works of early investigators because most of them did not pay any attention to the reaction of the solution which is an important factor as shown by St. Johnston 2 and qualitatively by Bottazzi. 3 The latter found the minimum surface tension to be at the isoelectric point, while the former showed the reverse to be the case. The present study deals with the relation between surface tension and the hydrogen ion concentration of egg albumin solutions together with an approximate calculation of the cross-sectional area of the egg albumin molecule.

As we are interested in the equilibrium surface tension, the drop weight method as recommended by Harkins and Brown 4 was adopted, the only modification being that the liquid was pushed over instead of being sucked through the capillary. A necessary condition in this static method is that sufficient time must be allowed for the surface to reach equilibrium. It is well known from the work of Du Noüy 5 and others that the surface tension of a freshly prepared egg albumin solution decreases on standing to a constant value. For the most dilute solutions we used, more than an hour must be allowed to reach equilibrium, while with more concentrated solutions 15-20 minutes will suffice. Egg albumin was recrystallized 3 times from ammonium sulphate solution and dialyzed until no ammonia or sulphate could be detected.