The combination of proteins, amino-acids, &c., with acids and alkalis. Part II.—Titration curves of amino-acids in presence of formaldehyde

Abstract

Grounds for an Investigation. 1.A detailed examination of the acid-base equilibrium and the titration curves of amino-acids in aqueous solution has already been made (1), but data have hitherto been lacking for these solutions in the presence of formal-dehyde,i.e., relating to the methylene derivatives of the amino-acids. 2.The addition of formaldehyde to amino-acids and the resulting increase in their acidity towards phenol phthalein (or thymol phthalein) constitutes the basis of the well-known Sørensen (“formol”) method (2) for their estimation by titration with soda; accordingly some knowledge of the acid-base constants and the titration curves of the systems in question is necessary before one can formulate the conditions (viz., the concentrations of formaldehyde and amino-acids, and the initial and finalphreadings, etc.) under which this estimation may be carried out with maximum accuracy.