Abstract. Solutions of stabilized 5 and 25% Normal Serum Albumin (Human) fractionated from plasma, placentas, and blends of these sources were subjected to repeated heatings for 120 h at 56 °C, interspersed with storage for 48 h at 4°C. Disc electrophoretic analyses showed that heating some solutions produced a reversible dimerization of the albumin related to the source, protein concentration, and number of heatings. Cellulose acetate electrophoresis showed that repeated heating produced a reduction in the amount of albumin with the formation of a component with a mobility slower than that of albumin. After eight heatings plasma albumin gelled; albumin from placental‐plasma blends partially gelled; there was no gelation of placental albumin after nine heatings.

Stabilized 5 and 25% normal serum albumin (human) derived from plasma, placentas and plasma-placental blends was subjected to repeated heating at 56 °C for 120 h, interspersed with storage at 4 °C for 48 h. Immunoelectrophoretic analyses showed that after the ninth heating, 5% plasma albumin developed a component which migrated in the α-globulin region and gave a reaction of nonidentity with albumin. This antigen, which was not detected in the other albumin samples, reacted with antiserum prepared against control 5% plasma albumin, indicating that it was present in the latter at an undetectably low concentration.

Stabilized 5 and 25% normal serum albumin (human) derived from plasma, placentas and plasma-placental blends was subjected to repeated heating at 56 degrees C for 120 h, interspersed with storage at 4 degrees C for 48 h. Immunoelectrophoretic analyses showed that after the ninth heating, 5% plasma albumin developed a component which migrated in the alpha-globulin region and gave a reaction of nonidentity with albumin. This antigen, which was not detected in the other albumin samples, reacted with antiserum prepared against control 5% plasma albumin, indicating that it was present in the latter at an undetectably low concentration.