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Counter-ion dissociation

Headgroup size reduced by dehydration Increased surfactant counter-ion dissociation... [Pg.1564]

Investigations of Counter-ion Dissociation of Sodium Poly(styrenesulfonates)... [Pg.244]

CE is a predestinate for study of polyelectrolyte counter-ion dissociation in free solution and study of the speed of this dissociation process. Counterion dissociation was studied with sodium poly(styrenesulfonates) of different molecular mass using indirect UV detection for quantification of sodium ions in the sample solution. The separation [39] was performed in an unmodified fused-silica capillary using a 0.005 mol L-1 imidazole buffer at pH 4.5 with potassium chloride as internal standard. In the electrophero-... [Pg.244]

As discussed, quantification of counter-ion dissociation by means of CE is not trivial because reliable results are only obtainable under the following conditions ... [Pg.246]

Using a glassy carbon electrode modified with a mercury film, Weber et al. [66] measured the association and dissociation rate constants for the complex formed between Pb + and the 18-crown-6 ether. It was found that Pb + forms a complex with 18-crown-6 with a stoichiometiy of 1 1 in both nitrate and perchlorate media. The formation constant, for the nitrate and perchlorate systems are (3.82 0.89) X 10 and (5.92 1.97) x lO mol Ls , respectively. The dissociation rate constants, are (2.83 0.66) x 10 with nitrate and (2.64 0.88) x 10 s with perchlorate as counter ion. In addition, the binding of Pb + with benzo-18-crown-6 embedded in a polymerized ciystalline colloidal array hydrogel has been also analyzed [67]. [Pg.45]

The dissociation of the counter-ions of micelles is a characteristic feature of ionic surfactants. For alkyl ether sulfates the degree of dissociation a of the counter-ions of the micelles has been determined by several authors by various methods (2, 26), With... [Pg.9]

When strong bases neutralize strong acids in solutions that have molar concentrations of 1 mol dm-3, the enthalpy of the reaction is observed to be -55.83 kJ mol - irrespective of the counter ions (e.g. the chloride ion derivable from HC1 and the sodium ion contained in NaOH) present. For example, when a standard solution (1 mol dm-3) of hydrochloric acid is neutralized by a standard solution (1 mol dm-3) of sodium hydroxide, the change in enthalpy of the reaction is -55.83 kJ mol-1. Because the strong acid HCI and the strong base NaOH are 100% dissociated in aqueous solution, theucutruli/atiun reaction may be written as ... [Pg.20]

It is well known that the association-dissociation reaction goes in both directions and that there is always some finite fraction of ion pairs [28]. Counter ions that form ion pairs do not participate in creating osmotic pressure accounting for such counter ions is thus important for the correct determination of the dimensions of the network. [Pg.138]

The experimental result obtained was explained by the formation of ion pairs between the charges of a network and counter ions. The theoretical analysis of this problem has shown that the degree of ion pairs formation very strongly (exponentially) depends on e (cf. Sect. 2.2). Thus, if the precipitant has a small dielectric constant e (e.g. dioxane) the degree of dissociation of ion pairs is sufficiently small and this fact leads to the decrease of the osmotic pressure of counter ions which defines the swelling of the gel and the point of the transition in the collapsed state. As a result, in this case the degree of swelling of the gel near the transition point is less pronounced than for other solvents and only a relatively small amount of the precipitant is required to reach this point. In... [Pg.150]

Since the -COOH groups of glutamic and aspartic acids are completely dissociated to -COO- at neutral pH, it is customary in the biochemical literature to refer to these amino acids as glutamate and aspartate without reference to the nature of the cation or cations present as counter ions. Such "-ate" endings are also used for most other adds (e.g., malate, oxaloacetate,... [Pg.52]

Poly(acrylic acid) is a typical polyelectrolyte and shows a dissociation reaction. When pH is high, the polymer chain is charged negatively and extends itself due to coulombic repulsion and thermal motion of counter ions which pull the charged side chains. [Pg.244]

Flory [3] formalized the equation of state for equilibrium swelling of gels. It consists of four terms the term of rubber-like elasticity, the term of mixing entropy, the term of polymer solvent interaction and the term of osmotic pressure due to free counter ions. Therefore, the gel volume is strongly influenced by temperature, the kind of solvent, free ion concentrations and the degree of dissociation of groups on polymer chains. [Pg.244]

Unlike superelectrophiles generated in the condensed phase, the gas phase species are not stabilized by solvation or association to counter ions. The stabilities of multiply charged small ions are dependent on their tendencies to dissociate into fragments in the gas phase.39 For diatomic systems, there are two possible routes of dissociation to atomic fragments the cleavage to a pair of monocations (eq 41) or cleavage to a dication and neutral species (eq 42). [Pg.43]


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See also in sourсe #XX -- [ Pg.244 ]




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