English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The change in the Na+ ion binding properties of a series of the anions of inorganic phosphates (phosphinate, cyclic polyphosphate, and linear polyphosphate) has been studied in order to see the transition from simple electrolyte to polyelectrolyte. Na+ ion activity measurement together with 23 Na NMR peak width measurement gave a consistent conclusion that about 100 of the chain-length is needed to show the binding properties independent of the chain-length in salt-free system. INTRODUCTION Even though a large number of studies have been reported on polyion-counterion binding up to present, rather few works have been carried out to study how the ion-binding properties are dependent on the size of the polyion. A family of inorganic polyphosphate anions of various polymerization number, n, may be a suitable example to investigate the transition from simple ion to polyion properties. In this work, phosphinate ion, PH2O2-(P I), and long-chain polyphosphate anions, PP-(average degree of polymerization, n, is several thousands), have been used as examples of simpleand polyions, respectively. Cyclic polyphosphate anions, (PnO3n n-), cPn (n=3,4,6, and 8), and linear polyphosphate anions, Pn (n=15, 35, 50, 85, 101, 127, and 150) have been used as examples of oligoions and polyions. The binding equilibria have been examined from the two different experimental approaches, i.e., without salt and with an excess salt. The first part of this work deals with a study on the binding of sodium ions to inorganic polyphosphate ions in the absence of salt; whereas the second part consists of the binding equilibrium studies of sodium ions and calcium ions to inorganic polyphosphate ions in the presence of an excess salt. Both a potentiometric and NMR techniques are utilized to investigate the bindings. EXPERIMENTAL CHEMICALS A series of sodium salts of the mixtures of linear polyphosphates were obtained by a solubility fractionation with acetone or gel chromatographic fractionation of Graham's salt[1,2]. Trisodium Received November 18, 1993; Accepted December 20, 1993 -37cyclo-triphosphate hexahydrate, Na3P3O9 6H2O was prepared in our laboratory. Tetrasodium cyclotetraphosphate tetrahydrate, Na4P4O12 4H2O, hexasodium cyclo-hexaphosphate hexahydrate, Na6P6O18 6H2O, and octasodium cyclo-octaphosphate heptahydrate, Na8P8O24 7H2O, were kindly offered by Dr. M. Watanabe in Chubu University. The purities of these cyclic phosphate samples were checked by an HPLC. Concentrations in monomole of all the phosphate stock solutions were determined colorimetrically with a Mo(V)-Mo(VI) reagent. Sodium phosphinate monohydrate, NaPH2O2 H2O, was analytical grade reagent, whose stock solution was standardized colorimetrically with the Mo(V)-Mo(VI) reagent after being oxidized by sodium hydrogen sulfite, NaHSO3, to orthophosphate. POTENTIOMETRIC TITRATION Emf measurement of Na+ ion was carried out at 25•}2•Ž by use of a glass electrode (Horiba Na+ ion selective electrode 1512A-06T) and a single junction type reference electrode (Horiba 2010A-06T), connected with a Hitachi-Horiba pH meter/F-7ss. The single ion activities of Na+ ion, a Na, in the sample solutions were determined by measuring the emf value, E, expressed by the following equation,

COUNTERION BINDING TO INORGANIC POLYPHOSPHATE ANIONS (II)