Casein has been spread from its aqueous solutions by different methods and it has been found that the modified band method is the most suitable for the study of protein films.
Effect of salts on the spreading of casein has been studied. The results obtained can be explained on the basis that two different factors, solubility and the electric charge of the protein molecule influence spreading.
Treatment of the protein with formaldehyde causes a decrease in spreading. Change in pH affects spreading of formolised casein to a smaller degree.
Sodium metaphosphate diminishes markedly the spreading of casein. Trichloracetic acid, however, has no effect.
Deaminisation of casein alters the spreading properties and gives unstable films on acidulated water. No films can be got on distilled water.
The spreading properties of an isodisperse fraction of casein have been studied. The limiting area of this fraction has been found to be of the same order as that of the original material.