a proton nmr method for the drtermination of salvation numbers of alkaline earth cations with hexamethyl phosphoramide (hmpa) in nitromethane (nm) as diluents is described. the method is based on monitoring the resonance frequency of hmpa protons as a function of hmpa / metal ion molar ratio at constant metalion concentration. the average salvation number of cations,  , at any hmpa / metal ion ...

The complexation of Alkali metal cations by the water-soluble p-sulfonic acid calix(4)arenewas thermodynamically characterized using spectrophotometeric data which are consistentwith the formation of a 1:1 complex resulting from electrostatic interactions between thesulfonato groups and alkali metal cations. In this study, we determined the formationconstants (log K) of the complexes and have c...

With a mean precipitation rate, much lower than that of the world, Iran is among the countries that face severe water challenges. The present study has dealt with the evaluation of hydrochemistry of Faryab spring water in Hormozgan Province, Iran. Four different composite water samples have been analyzed to detect major anions, cations, total dissolved solids, electrical conductivity, pH, and s...

the complexation of alkali metal cations by the water-soluble p-sulfonic acid calix(4)arenewas thermodynamically characterized using spectrophotometeric data which are consistentwith the formation of a 1:1 complex resulting from electrostatic interactions between thesulfonato groups and alkali metal cations. in this study, we determined the formationconstants (log k) of the complexes and have c...

the presence of cr(vi) in groundwater resources is governed by ph and eh of water and its compounds are generally soluble and have more toxicicity and mobility in oxidizing environments. in this article, the cr concentration in ophiolite units, in sediments, and in groundwater resources, and also its potential to contaminate the environment have been investigated in southeast of birjand. during...

Thermal behavior of various solid feldspars are different, namely those of bivalent cations show no change in the distribution of Al and Si atoms, whereas feldspars of univalent cations become more disordered with raising temperature. In the latter case Al atoms migrate from the sites they occupe at low temperatures and interchange positions with the Si atoms. At high temperatures (but stil...

Ion chromatography (IC), developed by Small et al. [1], is widely recognized as a simple and powerful analytical technique for the determination of various inorganic and organic anions and cations [2]. Sulfonated and carboxylated polymer resins and silicas are commonly employed as cation−exchange stationary phases in IC for cationic species. The application of unmodified silica gels as cation−e...