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A potentiometric determination of the dissociation constants of glycine in {14.926 mass% urea + water} mixed solvent at 278.15 to 318.15 K
Author(s) -
Yuan ChangBo,
Yang JiaZhen
Publication year - 1991
Publication title -
chinese journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.28
H-Index - 41
eISSN - 1614-7065
pISSN - 1001-604X
DOI - 10.1002/cjoc.19910090601
Subject(s) - chemistry , activity coefficient , solvent , potentiometric titration , dissociation constant , extrapolation , dissociation (chemistry) , thermodynamics , electrolyte , inorganic chemistry , analytical chemistry (journal) , aqueous solution , electrode , organic chemistry , mathematical analysis , biochemistry , physics , receptor , mathematics
First and second thermodynamic dissociation constants of glycine at five temperatures from 278.15K to 318.15K in {14.926 mass% urea + water} mixed solvent have been determined from precise emf measurements of hydrogen‐silver chloride electrodes in two cells, (A) and (B), without liquid junction, by the new method of polynomial approximation proposed on the basis of Pitzer's electrolytic solution theory in our previous papers, as compared with traditional extrapolation on the basis of the extended Debye‐Hückel equation. The results obtained from both methods are in agreement within experimental error. The thermodynamic quantities ΔG °, ΔH °, ΔS ° and ΔC p ° were derived from the dependence of p K ° values on temperature, and p K 1 = 367.60 ( K / T ) − 0.3973 + 3.108 × 10 −2 ( T / K ), whereas p K 2 , = 2028.77 ( K / T ) + 2.8791 – 2.110 × 10 −3 ( T / K ). The results have been discussed in terms of the solute‐solvent interaction and have been compared with those results in water and in other mixed solvents.