Hydrating ions

A number of refinements and applications are in the literature. Corrections may be made for discreteness of charge [36] or the excluded volume of the hydrated ions [19, 37]. The effects of surface roughness on the electrical double layer have been treated by several groups [38-41] by means of perturbative expansions and numerical analysis. Several geometries have been treated, including two eccentric spheres such as found in encapsulated proteins or drugs [42], and biconcave disks with elastic membranes to model red blood cells [43]. The double-layer repulsion between two spheres has been a topic of much attention due to its importance in colloidal stability. A new numeri-... 

The ability of living organisms to differentiate between the chemically similar sodium and potassium ions must depend upon some difference between these two ions in aqueous solution. Essentially, this difference is one of size of the hydrated ions, which in turn means a difference in the force of electrostatic (coulombic) attraction between the hydrated cation and a negatively-charged site in the cell membrane thus a site may be able to accept the smaller ion Na (aq) and reject the larger K (aq). This same mechanism of selectivity operates in other ion-selection processes, notably in ion-exchange resins. 

Many ionic halides dissolve in water to give hydrated ions. The solubility of a given halide depends on several factors, and generalisations are difficult. Ionic fluorides, however, often differ from other halides in solubility. For example, calcium fluoride is insoluble but the other halides of calcium are highly soluble silver fluoride. AgF, is very soluble but the other silver halides are insoluble. 

The chemistry of vanadium compounds is related to the oxidation state of the vanadium. Thus, V20 is acidic and weaMy basic, VO2 is basic and weaMy acidic, and V2O2 and VO are basic. Vanadium in an aqueous solution of vanadate salt occurs as the anion, eg, (VO ) or (V O ) , but in strongly acid solution, the cation (V02) prevails. Vanadium(IV) forms both oxyanions ((V O ) and oxycations (VCompounds of vanadium(III) and (II) in solution contain the hydrated ions [V(H20)g] and [V(H20)g], respectively. 

In the first step the hydrated ion and ligand form a solvent-separated complex this step is believed to be relatively fast. The second, slow, step involves the readjustment of the hydration sphere about the complex. The measured rate constants can be approximately related to the constants in Scheme IX by applying the fast preequilibrium assumption the result is k = Koko and k = k Q. However, the situation can be more complicated than this. - °... 

The attractions between the water molecules interacting with, or hydrating, ions are much greater than the tendency of oppositely charged ions to attract one another. The ability of water to surround ions in dipole interactions and... 

Water-soluble pAM neutral polymer interacts with ions of the solution through the complex formation between amide groups and hydrated ions. 

Arrangement O, in which water dipoles completely cover the surface of the metal with the locus of the centres of the hydrated ions forming the O.H.P. 

At each interface the interfacial potential will depend upon the chemical potentials of the species involved in the equilibrium. Thus at the Zn/Zn electrode there will be a tendency for zinc ions in the lattice to lose electrons and to pass across the interface and form hydrated ions in solution this tendency is given by the chemical potential of zinc which for pure zinc will be a constant. Similarly, there will be a tendency for hydrated Zn ions in solution to lose their hydration sheaths, to gain electrons and to enter the lattice of the metal this tendency is given by the chemical potential of the Zn ions, which is related to their activity. (See equation 20.155.) Thermodynamically... 

In the nineteenth century a liquid was thought to be like a gas. In a gas a molecule makes a collision, travels freely, makes another collision, again travels freely, and so on. It was thought that a liquid should be described in the same way—only with much shorter free paths. In a solution each solute particle would moke frequent collisions with solvent molecules. But in an aqueous solution containing atomic ions the question was asked between collisions is the atomic ion traveling alone, or does it travel with water molecules attached to it Electrochemists unanimously came to the conclusion that to each species of atomic ion several water molecules were attached, to form a hydrate when they spoke of the mobility of the ion, they meant the mobility of this large rigid hydrated ion. 

In equation (q) only the fully ionised form of EDTA, i.e. the ion Y4 , has been taken into account, but at low pH values the species HY3, H2Y2, H3 Y and even undissociated H4Y may well be present in other words, only a part of the EDTA uncombined with metal may be present as Y4. Further, in equation (q) the metal ion M"+ is assumed to be uncomplexed, i.e. in aqueous solution it is simply present as the hydrated ion. If, however, the solution also contains substances other than EDTA which can complex with the metal ion, then the whole of this ion uncombined with EDTA may no longer be present as the simple hydrated ion. Thus, in practice, the stability of metal-EDTA complexes may be altered (a) by variation in pH and (b) by the presence of other complexing agents. The stability constant of the EDTA complex will then be different from the value recorded for a specified pH in pure aqueous solution the value recorded for the new conditions is termed the apparent or conditional stability constant. It is clearly necessary to examine the effect of these two factors in some detail. 

Primarily the sum of carbonate, bicarbonate and hydrate ions in water, but phosphate, silicate etc. may also contribute partially to alkalinity. Normally expressed as ppm (mg/1) CaC03. Phenolphthalein alkalinity (P Aik.) is that portion of alkalinity titrated with acid to pH 8.2 end-point, while total alkalinity (T Aik. or M Aik.) is that titrated with methyl orange indicator to pH 4.2 endpoint. 

Samarium, tris(triphenylphosphine oxide)bis-(diethyldithiophosphato)-structure, 1,78 Samarium complexes dipositive oxidation state hydrated ions, 3, 1109 Samarium(III) complexes salicylic acid crystal structure, 2, 481 Sampsonite, 3, 265... 

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