Adsorption von Elektrolyten an Kartoffelstärke. Wärmeentwicklung, Sedimentvolumen, Kontraktion

Adsorption of Electrolytes on Potato Starch. Heat Development, Swelling and Contraction. On addition of electrolyte solutions to moist potato starch an adsorption takes place, accompanied by the development of heat and by swelling. In alkali salts both phenomena proceed rapidly, usually within a few minutes, and reversible. In potassium salts the evolution of heat depends on the anion (in the sequence of the lyotropic series: rhodanid strongly adsorbed with high thermal effect, sulphate weakly adsorbed with hardly any effect). The amount of swelling on the contrary is hardly different in this case, and the amount of contraction is the same. In this respect there is a contrast with earlier research on the adsorption of water in air-dry starch in which heat development and contraction proved to be proportional. Calcium hydroxyde is adsorbed in much higher quantities than those of the monovalent cations and this adsorption takes a much longer time (up to 50 minutes). The adsorption of hydroxyl ions from monovalent hydroxydes is augmented by the addition of neutral salts. The practical combination NaOH-Na2SO4 is studied.