Acid–Base Properties of Vitamin B₁ in an Aqueous Solution

Abstract—The dissociation constant of thiamine hydrochloride in an aqueous solution at 298.15 K and ionic strengths of 0.5, 1.0, and 1.5 (using potassium nitrate as the background electrolyte) is determined via potentiometric titration. The heat effects of the dissolution of crystalline thiamine hydrochloride in water and solutions of potassium hydroxide at 298.15 K and different ionic strengths of solution are measured, and the standard thermodynamic characteristics of dissociation are obtained on a variable-temperature calorimeter with an isothermal shell. The absorption spectra of aqueous solutions of thiamine hydrochloride in the pH range of 2.8 to 11.4 at 298.15 K are studied using spectrophotometric measurements. Vitamin B₁ in aqueous solutions is found to behave like a monobasic acid. The thermodynamic characteristics of the dissociation of thiamine hydrochloride in an aqueous solution are determined under standard conditions.