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...

Recently solution scanometry, as a new, simple, fast, portable, and economic method was introduced for determination of acidity constants of indicator and dyes. In this study, a method was applied for the determination of the acidity constant of p-Rosolic acid (RA) and Bromoxylenol blue (BXB) indicators. The method is based on scanning of Plexiglas® sheet containing colored solutions with a fla...

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 acidity constants of the compounds, including five-membered heterocyclic (pyrrole, thiophene, furan or thiazole) ring systems were determined at 25oC in aqueous solitions, applying UV-Vis spectroscopic method that uses absorbance diagrams,. In order to explain the pKa values obtained, also the molecule conformations of the bases and their corresponding conjugate acids were investigated, app...

The macro acidity constants valid for aqueous solutions of several adenine, guanine, and hypoxanthine derivatives are summarized. It is shown how the application of the corresponding constants, e.g., for 7,9-dimethyladenine, allows a quantification of the intrinsic acidic properties of the (N1)H0/+ and (N7)H+ sites via micro acidity constants, and how to use this information for the calculation...

the acidity constants of some amino acids (am) were determined by potentiometric ph titration. the stability constants of the 1:1 complexes formed between m2+: ca2+, mg2+, mn2+, co2+, ni2+, cu2+ or zn2+ and am2-, were determined by potentiometric ph titration in aqueous solution (i = 0.1 m, nano3, 25°c). the order of the stability constants was reported. it is shown that the stability of the bi...

The surface physical-chemical characteristics of a class F coal fly ash were studied in an effort to establish a quantitative understanding of metal adsorption. The ash surface acidity (acid site density and acidity constant), surface electrical characteristics, and adsorption constants for selected heavy metal ions were determined using a batch titration method, an electrophoretic method, and ...

Article history: Received March 28, 2013 Received in Revised form August 28, 2013 Accepted 27 November 2013 Available online 28 November 2013 In this work, acidity constants protonated form of 4.4'-bis astilbene-2,2'-disulfonic-disodium salts (TRIAZ) have been determined spectrophotometrically and spectrofluorimetrically at 25C and ionic strength of 0.1M KNO3. A program based on MCR-ALS applied...

The dinucleotide d(pGpG) is an often employed DNA model to study various kinds of interactions between DNA and metal ions, but its acid-base properties were not yet described in detail. In this study the six deprotonation reactions of H4[d(pGpG)]+ are quantified. The acidity constants for the release of the first proton from the terminal P(O)(OH)2 group (pKa = 0.65) and for one of the (N7)H+ si...