Hexacyanoferrate lll ions

Measurements of the rate of oxidation of D-galactose by hexacyano-ferratedll) Ions In the presence of ethylenedlamlne have shown that the reaction Is first order In sugar and hydroxide Ion, but zero order In the hexacyanoferrate(lll) Ion. A general mechanism In-... 

Probably the most extensively applied masking agent is cyanide ion. In alkaline solution, cyanide forms strong cyano complexes with the following ions and masks their action toward EDTA Ag, Cd, Co(ll), Cu(ll), Fe(ll), Hg(ll), Ni, Pd(ll), Pt(ll), Tl(lll), and Zn. The alkaline earths, Mn(ll), Pb, and the rare earths are virtually unaffected hence, these latter ions may be titrated with EDTA with the former ions masked by cyanide. Iron(lll) is also masked by cyanide. However, as the hexacy-anoferrate(lll) ion oxidizes many indicators, ascorbic acid is added to form hexacyanoferrate(ll) ion. Moreover, since the addition of cyanide to an acidic solution results in the formation of deadly... 

Li Y, Petroski J, El-Sayed MA (2000) Activation energy of the reaction between hexacyanoferrate(lll) and thiosulfate ions catalyzed by platinum nanoparticles. J Phys Chem B 104 10956... 

A.K. Jain, R.P. Singh, and C. Bala, Studies on an Araldite-based membrane of copper hexacyanoferrate(lll) as a caesium-ion-sensitive electrode. J. Chem. Technol. BiotechnoL, Chem. Technol. 34A, 363—366 (1984). 

Iron(III) ions cannot be detected in a solution of hexacyanoferrate(lll) with the usual reactions. The complex has to be decomposed first by evaporating with concentrated sulphuric acid or by igniting a solid sample, as described with hexacyanoferrate(II) (cf. Section 3.21, reaction 5). 

If phenolphthalein is used as an indicator for hydroxyl ions and potassium hexacyanoferrate(lll) as an indicator for iron(II) ions, the anode and cathode areas can be made visible in the case of corroding iron. If, for example, an iron nail is placed in a gelatin solution mixed with these two indicators, after a while the head and point of the nail start to turn blue because of the formation of Prussian blue, whereas the middle of the nail turns red. The experiment shows that it is mainly the anodic process that takes place at the mechanically worked points, whereas the cathodic process with the formation of hydroxyl ions occurs in the middle of the nail. 

Poly(diallyldimethylammonium chloride) (PDADMAC) and ferri-/ferrocyanide show a similar behavior [233]. In most cases, the ferri-/ferrocyanide (trivalent/ tetravalent hexacyanoferrate[lll]/[ll]) couple exhibits an unexpected interaction pattern with strong cationic polyelectrolytes. Hereby, the trivalent ferricyanide favors complexation compared with the tetravalent ferrocyanide [234, 235]. Although the higher charged ferrocyanide is supposed to release a higher number of monovalent counterions, this entropic contribution is less dominant for the ferrocyanide. This conclusion was derived from entropy measurements [232], clearly emphasizing the enthalpic repulsion between the highly hydrated, weakly polarizable ferrocyanide and the somewhat hydrophobic polymeric backbone [236]. This leads to pronounced ion-specific effects. In contrast, some systems... 

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