Abstract
Ferric hydroxide was peptized by pouring the precipitate into aqueous solutions of various amino acids and boiling for 8 hr. The degree of peptization was evaluated by the concentration of ferric hydroxide in the sol thus formed. For this purpose, the concentration was determined by chelatometry after decomposition of colloidal particles into ferric ions. The adsorption of hydrogen ions on ferric hydroxide particles in amino acid solutions was measured as well. In the case of glycine, L-α-alanine, DL-α-aminobutyric acid, L-valine, and L-isoleucine, the addition of a small amount of hydrochloric acid increased the degree of peptization. However, no peptization took place in the case of L-arginine and L-lysine hydrochlorides, and L-methionine. In spite of no difference between glycine and L-α-alanine in the amount of hydrogen ion adsorbed on ferric hydroxide particles, the degree of peptization and stability of sol were higher in L-α-alanine than in glycine. It was found that L-α-alanine is one of the most effective peptizer of ferric hydroxide among amino acids, and it was concluded that the adsorption of amino acids except L-methionine promotes peptization.
