THERMODYNAMIC PARAMETERS FOR THE FORMATION OF GLYCINE COMPLEXES WITH MAGNESIUM(II), CALCIUM(II), LEAD(II), MANGANESE(II), COBALT(II), NICKEL(II), ZINC(II) AND CADMIUM(II) AT DIFFERENT TEMPERATURES AND IONIC STRENGTHS, WITH PARTICULAR REFERENCE TO NATURAL FLUID CONDITIONS

Protonation constants and Mg2+-, Ca2+-, Pb2+-, Mn2+-, Co2+-, Ni2+-, Cu 2+-, Zn2+- and Cd2+-glycine complex formation constants have been dete rmined in different aqueous media at different temperatures. Salt effe cts are explained by a complex formation model which takes into accoun t the formation of weak species. From the temperature dependence of th e formation constants, thermodynamic parameters Delta H-Kelvin (and in some cases Delta C-p(Kelvin)) have been obtained. A rigorous analysis of literature data, together with experimental findings, allows recom mended formation parameters, in the ranges 0 less than or equal to I-e less than or equal to 1 mol l(-1) (I-e is the effective ionic strengt h) and 5 degrees C less than or equal to T less than or equal to 45 de grees C, to be obtained. Because the proposed model can be used in any electrolyte mixture in the above I and T ranges, the speciation in se awater, and other natural fluids, can be simulated by appropriate comp uter programs. The validity of the present approach which takes into a ccount the ionic strength dependence of formation constants, together with the concepts of effective ionic strength and complex formation mo del, is discussed.