Cholic acid, deoxycholic acid, chenodeoxycholic acid, and ursodeoxycholic acid were purified by a foam fractionation method. Using thermogravimetric analysis, the attached water molecule was found to be completely removed from solids of the latter three at 100°C, while cholic acid still had one water molecule of crystallization per two cholic acid molecules at that temperature. The acidity cons...

A spectrophotometric method is used to determine the acidity constants of some derivatives of 9,10-anthraquinone in binary methanol-water mixtures at 25 °C. There is a linear inverse relationship between pKa of all acids and the mole fraction of methanol in the mixed solvent. The influence of substituents in the molecular structure on the ionization constants is discussed.  

The acidity and stability constants of M(Trp) M: Cu, Cu(Bpy)2+, and Cu(Phen)2+ complexes, were determined by potentiometric pH titration. It is shown that the stability of the binary Cu(Trp) complex is determined by the basicity of the carboxylate group on one side and amino group on the other side. It is demonstrated that the equilibrium, Cu(Har)2+ + Cu(Trp) Cu(Har)(Trp) + Cu, is displacement ...

the complexation reactions between methylthymol blue (mtb) and co2+, ni2+, cu2+, zn2+ and pb2+ ions have been studied in different water-methanol mixtures at ph 4.45 and 25 °c by a spectrophotometric technique. the stepwise stability constants of the resulting 1:1 and 2:1 (metal ion to ligand) complexes were determined from the absorbance-mole ratio data. it was found that the overall stability...

The stability constants and complexation reaction between L-glutamine, L-arginine andglycine with Zn (II) , Co (II) and Ni (II) were studied potentiometrically in aqueous solution at25° C and μ=0.1 M KNO3. The overall stability constants log β´s of all species are obtained bycomputer refinement of pH-volume data using BEST computer program. Several models weretested and the lowest δFIT, the bes...

The acid–base properties of calcon (1-(2-hydroxy-1-naphthylazo)-2-naphthol-4-sulfonic acid) in water and mixed water–organic solvents at 25 °C at an ionic strength of 0.10 M are studied by a multiwavelength spectrophotometric method. The organic solvents used were the amphiprotic (methanol), dipolar aprotic (dimethylsulfoxide), and low basic aprotic (acetonitrile). To evaluate the pH absorbance...

the acid-base equilibria of glycine have been studied in different aqueous solutions of 1,4-dioxane(0-50 % by v/v) using potentiometric method. in this study, the macro and micro protonationconstants of the amino acid and its tautomeric constant have been determined at 25 °c and constantionic strength 0.1 mol dm-3 (nacl). the protonation and the tautomeric constants of glycine indifferent binar...

Cumulative formation constants for the interaction of phenylboronic acids with 1,2-diols and structurally related α-hydroxy carboxylic acids were determined by potentiometric titration in aqueous solution. Although there is a significant electronic effect on the acidity of phenylboronic acid (ρ = 2.1), there is no marked electronic effect on the stability of the complexes. Rather, the complexes...