Mixtures of anions

The presence of several anions in these ionic liquids has the effect of significantly decreasing the melting point Considering that the formation of eutectic mixtures of molten salts is widely used to obtain lower melting points, it is surprising that little effort has been put into identifying the effects of mixtures of cations or anions on the physical properties of other ionic liquids [17]. 

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Titanium tetrachloride is hydrolysed by water, to give a mixture of anions, for example [Ti(OH)Cl5]" and [TiClg] , together with some hydrated titanium dioxide (Ti02.4H2O is one possible hydrate, being equivalent to [Ti(0H)4(H20)2]). This suggests that titanium dioxide is amphoteric (see below). 

Surfactants in E/ectroc/eaners. Surfactants typically consist of a long-chain hydrocarbon molecule having a solubilising or water-loving group which can be anionic, cationic, or nonionic when solubilized. Thousands of surfactant products are marketed, usually under trade names (32). In commercially formulated electrocleaners, surfactants are usually anionic, and often mixtures of anionics and nonionics. 

In the case of ions, the repulsive interaction can be altered to an attractive interaction if an ion of opposite charge is simultaneously adsorbed. In a solution containing inhibitive anions and cations the adsorption of both ions may be enhanced and the inhibitive efficiency greatly increased compared to solutions of the individual ions. Thus, synergistic inhibitive effects occur in such mixtures of anionic and cationic inhibitors . These synergistic effects are particularly well defined in solutions containing halide ions, I. Br , Cl", with other inhibitors such as quaternary ammonium cations , alkyl benzene pyridinium cations , and various types of amines . It seems likely that co-ordinate-bond interactions also play some part in these synergistic effects, particularly in the interaction of the halide ions with the metal surfaces and with some amines . 

The performance potential of synergistic mixtures of anionics (e.g., alkanesulfonates) and amine oxides with hydroxyethylene groups was already analyzed some years ago [89]. It was shown that lauryldi(hydroxyethylene)amine N-oxide lowers the Zein values of the mixtures with alkanesulfonates. 

As mentioned, AOS is a complex mixture of anionic active substances the nature of which is dependent on the quality of the olefin feed and the manufacturing processes employed. Formulations utilizing AOS are developed according to the level and type of these active species. Analytical procedures are therefore required to define their level and nature. 

In the same year, Fulda and Tieke [75] reported on Langmuir films of monodisperse, 0.5-pm spherical polymer particles with hydrophobic polystyrene cores and hydrophilic shells containing polyacrylic acid or polyacrylamide. Measurement of ir-A curves and scanning electron microscopy (SEM) were used to determine the structure of the monolayers. In subsequent work, Fulda et al. [76] studied a variety of particles with different hydrophilic shells for their ability to form Langmuir films. Fulda and Tieke [77] investigated the influence of subphase conditions (pH, ionic strength) on monolayer formation of cationic and anionic particles as well as the structure of films made from bidisperse mixtures of anionic latex particles. 

Surfactants have been widely used to reduce the interfacial tension between oil and soil, thus enhancing the efficiency of rinsing oil from soil. Numerous environmentally safe and relatively inexpensive surfactants are commercially available. Table 18.6 lists some surfactants and their chemical properties.74 The data in Table 18.6 are based on laboratory experimentation therefore, before selection, further field testing on their performance is recommended. The Texas Research Institute75 demonstrated that a mixture of anionic and nonionic surfactants resulted in contaminant recovery of up to 40%. A laboratory study showed that crude oil recovery was increased from less than 1% to 86%, and PCB recovery was increased from less than 1% to 68% when soil columns were flushed with an aqueous surfactant solution.74-76... 

BASIS OF MANUAL PHOTOMETRIC TITRATION. The determination of anionic surfactants by a photometric titration employs a cationic indicator to form a coloured complex with the surfactant which is insoluble in water but readily soluble in chlorinated solvents (1 ). The end point of the titration occurs when there is a loss of colour from the organic phase. A considerable improvement in this technique is achieved by the use of a mixture of anionic and cationic dyes (4 ), for example disulphine blue and dimidium bromide (Herring s indicator (3)). The sequence of colour changes which occurs during the two phase titration of an anionic surfactant (AS) with a cationic titrant (CT) using a mixed indicator consisting of an anionic indicator (AD) and cationic indicator (CD) is summarised in Scheme 1 ... 

Particularly effective is a mixture of anionic and nonionic agents, such as a mildly anionic sulphated alcohol ethoxylate with a nonionic alcohol ethoxylate. Ideally, foaming agents should ... 

Chrisstoffels, L. A. J. de Jong, F. Reinhoudt, D. N. Sivelli, S. Gazzola, L. Casnati, A. Ungaro, R. Facilitated transport of hydrophilic salts by mixtures of anion and cation carriers and by ditopic carriers. J. Am. Chem. Soc. 

Specific-ion electrodes are expensive, temperamental and seem to have a depressingly short life when exposed to aqueous surfactants. They are also not sensitive to some mechanistically interesting ions. Other methods do not have these shortcomings, but they too are not applicable to all ions. Most workers have followed the approach developed by Romsted who noted that counterions bind specifically to ionic micelles, and that qualitatively the binding parallels that to ion exchange resins (Romsted 1977, 1984). In considering the development of Romsted s ideas it will be useful to note that many micellar reactions involving hydrophilic ions are carried out in solutions which contain a mixture of anions for example, there will be the chemically inert counterion of the surfactant plus the added reactive ion. Competition between these ions for the micelle is of key importance and merits detailed consideration. In some cases the solution also contains buffers and the effect of buffer ions has to be considered (Quina et al., 1980). 

Bismuth compounds have been used for treating gastrointestinal disorders for more than two centuries (451). These include bicarbonate, nitrate and salicylate salts, and colloidal bismuth subcitrate. These are all Bi(III) compounds Bi(V) is usually a strong oxidant. Their structures are largely unknown and often contain a mixture of anionic ligands. This reflects the strong tendency of Bi(III) to hydrolyze and form stable hydroxo and oxo complexes. The first pKa of Bi(III) in water is ca. 1.5. Bismuth(III) has a variable coordination number, from 3 to 10. 

In this triad the simple polynuclear neutral carbonyls are unknown the compound [Pt(CO)2] probably corresponds to a mixture of anions [Pt3(CO)6] 2 (n — 10) 60). Stable polynuclear species have been obtained only in the presence of ligands less n-acidic than CO, or as anions. 

The mixture of anionic fluorinated alkylphosphinic and -phosphonic acid surfactants with perfluorinated alkyl moieties was examined using ESI-FIA-MS-MS(—). For CID in the negative mode, precursor ions at m/z 399, 499 and 599 were selected [22]. From all precursor ions only one product ion at m/z 79 ([PO3]—) besides the [M — H] ion was... 

The target HLB can be obtained by using a mixture of anionic surfactant (HLB = 9.4) and nonionic surfactant HLB = 16.7) in the right proportions (1 3.75 based on the formula in Table 3). Such mixing of anionic and nonionic surfactants is expected to lower the individual CMC s and thus an increase of the soil solubilization capacity. The surfactants in the product should be in spherical micelle phase to give a transparent/translucent appearance and small viscosity (Table 6). 

Fig. 3.89. Separation of the six anionic dyes under gradient conditions in 5 pm Hypersil ODS, 100 X 3 mm i.d. column. Eluent (first solution) 25 mM TBAN03, 25 mM acetate buffer pH 4.7 (second solution) methanol. Flow rate, 0.7 ml/min injection volume, 20 pV, gradient indicated in the Figure sample solution, mixture of anionic dyes, concentration of each 25 pg/ml Absorption detection at 500 nm. Reprinted with permission from R. M. Seifar et al. [150].

As logical as this diagnostic method is, one needs to realize its lack of absolute applicability. The observed magnitude of the kinetic isotopic effect is not great, and the aforementioned statement of independence of the electron affinity from the increase in molecular mass of the substrate is not obvious. This postulate should be proved in each case. Benzophenone, taken as an isotopic mixture of C=0 and C=0 gives a mixture of anion-radicals with a decreased proportion of C=0 isotomer when reduced with potassium in HMPA (Stevenson et al. 1987b). In effect, this means that for the heavier isotopomer of benzophenone, the electron affinity is smaller. 

A potentiometric study of polymeric anions of molybdenum in nitrate melts has resolved apparent contradictions in earlier work and confirmed that [Mo207] ", rather than [Mo30,o] , is the polymeric anion in equilibrium with [MoOj ] The crystal structure of K2[Mo,07] has been shown to involve chains of M0O4 tetrahedra and MoO octahedra " and the dissociation of molten Na2[W207] to Na and a mixture of anions including [W04], [W207] , and has been confirmed. " The results of other... 

Bourrel M, Bernard D, Graciaa A (1984) Properties of binary mixtures of anionic and cationic surfactants Micellization and Microemulsions. Tenside Deterg 21 311-318... 

Scamehorn et. al. (19) reported the adsorption isotherms for a binary mixture of anionic surfactants. A formal adsorption model developed for single surfactant systems ( ) was extended to this binary system and shown to accurately describe the mixed adsorption isotherms (19). That theoretically based model was very complex and is probably not feasible to extend beyond two surfactant components. 

In suppressed-ion anion chromatography (Figure 26-4a), a mixture of anions is separated by ion exchange and detected by electrical conductivity. The key feature of suppressed-ion chromatography is removal of unwanted electrolyte prior to conductivity measurement. 

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