Cation compositions

Most of the data from the complete set at each station do not show a substantial charge imbalance, considering that the cationic composition should be balanced by the anionic composition. The magnitude of the imbalance is best seen by using the Normalised Inorganic Charge Balance (NICB = X — X+/X + X+ 100). Most points plot within the 5% field with a mean NICB close to 0% and a standard deviation of 2% for all the Ebro monitoring stations and the tributaries. 

The partial structural decomposition of the POM, as evidenced by (i) the formation of small amounts of crystalline M0O3, and (ii) the change in the cationic composition. In regard to the latter point, the ammonium content in the catalyst decreased, and its place in the cationic position of the POM was occupied by Mo ions. The formation of Mo dimeric species was shown in the downloaded catalysts, which were made of neighboring Mo ions located in the anion and in the counteranion cationic position." ... 

Fig. 11 Ideal local order for a cation composition M /M of a 2 1, and b 3 1. The circles represent the correlations between the cations P2 P6 defined in the text...

The effect of solution chemistry on the speciation of the organic contaminant 1-naphtol (1-hydroxynaphthalene) and its complexatiom with humic acid is reported by Karthikeyan and Chorover (2000). The complexation of 1-naphtol with humic acid (HA) was studied during seven days of contact, as a function of pH (4 to 11), ionic strength (0.001 and 0.1 M LiCl), and dissolved concentration (DO of 0 and 8 mg L ) using fluorescence, UV absorbance, and equilibrium dialysis techniques. In a LiCl solution, even in the absence of HA, oxidative transformation of 1-naphtol mediated by was observed. In addition, the presence of humic acid in solution, in the absence of DO, was found to promote 1-naphtol oxidation. These reactions are affected by the solution chemistry (pH, ionic strength, and cation composition). 

Fig. 2. Triangular plot of Ca, Na, and A-site vacancies in pyrochlore from Vishnevogorskii calculated from structural formulae normalized to two B-site cations. Compositions of primary pyrochlore plot near the Ca-Na join (solid symbols). Compositions of the altered areas move toward the Ca-vacancy join, then along this join toward the top of the triangle.

After the experiments, significant quantities of newly formed minerals were observed at the cold extremity of the tube, pointing to a fast material transport by diffusion from the hot to the cold end of the tube. The following spatial distribution of newly formed phases, reflecting the temperature profile, was observed in both runs (Fig. 8) quartz + K-feldspar + plagioclase + Mg-rich saponites (hot extremity) quartz + K-feldspar + plagioclase (middle of the tube) and alkaline or Ca-rich clays + quartz + plagioclase (cold extremity). The cation composition of the phyllosilicates was similar in both experiments. Some newly fonned quartz crystals... 

Arai and co-workers investigated the effects of cation composition in the mirror plane of Mn-substituted hexaaluminates.5,15 Investigation of a series of rare-earth-based hexaaluminates (AMnAluOi9, A=La, Pr, Nd, Sm) prepared via hydrolysis of alkoxides and calcined at 1200 °C for 5 h showed that surface area increases with the ionic radius of A. The La-substituted sample, the largest cation of the series, showed a surface area of 15 m2/g, which compared with 5 m2/g for the Sm-substituted one, i.e., the smallest cation of the series. These data are consistent with the mechanism of sintering resistance reported above. Indeed, it is expected that the larger the cation, the more difficult its diffusion along the c axis. 

The differences in cation compositions are probably due to the fact that phases containing these ions (illite, smectite, etc.) have sufficient time to form in natural systems but did not form in the experimental system. The high HCO3 content of the experimental system is due to contact with an infinite reservoir of CO2 having a partial pressure of 0.1 atmosphere. 

Two synthesis variables seemed to have received most attention in the work reviewed here, the cation composition and the nature and source of the aluminosilicate reactant. Extensive use of mixed bases of the alkali, alkaline earth, and organic cations have been reported as well as a wide variety of reactant aluminosilicates including solutions, hydrogels, glasses, kaolin (raw and calcined), and naturally occurring zeolites. 

Tables II and III are presented as an initial attempt to establish a broad correlation between crystallization and structure in terms of cation composition. The extensive assumptions and uncertainties involved are well recognized including acceptance of assignment of framework type based on similarity of x-ray powder diffraction patterns, exclusion of some polyhedral cages found in zeolite structures (62) f the relative concentrations of cations in mixtures, variables other than cation, and the possible presence of impurity cations not reported but derived from reagents or reaction vessels.

Table II. Unit Cells and Cation Compositions in Zeolite L...

Finally complexes have been obtained having two different cations and a partially oxidized Pt(CN)4 chain. These molecules show significant changes in electrical conductivity with small differences in cation composition.295,296... 

Chemical analysis for cation composition, cation/anion ratio, and chemical impurities. 

Control over the silver halide environment is possible by varying the anion and cation compositions as illustrated below and in Figure 1 ... 

Cationic Composition of the Samples HC, NaHC, KHC, CaHC, and MgHC... 

Note The error in the determination of the cationic composition is 0.1 mequiv/g. 

Cationic Composition of the Samples NiNaHC, NiKHC, NiCaHC, and NiMgHC... 

The cathodic mechanism is complex and it depends on the melt composition, especially the acidity of the electrolyte, namely the cation composition. In less acidic electrolytes (see below) the peroxide mechanism prevails [341,342] ... 

Very recently Geus and co-workers [44, 45] have applied another method based on chemical complexes. This is the complex cyanide method to prepare both monocomponent (Fe or Co) and multicomponent Fischer-Tropsch catalysts. A large range of insoluble complex cyanides are known in which many metals can be combined, e.g. iron(n) hexacyanide and iron(m) hexacyanide can be combined with iron ions, but also with nickel, cobalt, copper, and zinc ions. Soluble complex ions of molybdenum(iv) which can produce insoluble complexes with metal cations are also known. Deposition precipitation (Section A.2.2.1.5) can be performed by injection of a solution of a soluble cyanide complex of one of the desired metals into a suspension of a suitable support in a solution of a simple salt of the other desired metal. By adjusting the cation composition of the simple salt solution, with a same cyanide, it is possible to adjust the composition of the precursor from a monometallic oxide (the case when the metallic cation is identical to that contained in the complex) to oxides containing one or several foreign elements. 

In this paper we shall summarize our recent findings concerning the nature and distribution of species present in silicate and aluminosilicate solutions and gels. Particular attention will be focused on establishing the effects of pH, cation composition, Si/Al ratio, and solvent composition. 

Amine Additives. It is precisely in this area, suppressing an undesired product in favor of the desired one, that additives can be most useful. High silica zeolites have been formed in the presence of amine additives. Vaughan (16) has prepared faujasite with 7.0 SiC>2/Al2(>3 (24.52 A0) by addition of bis-(2-hydroxyethyl) dimethyl ammonium chloride in a slurry composition whose cation composition is 69% Na and 31% organic template (T). To scale this product up to commercial synthesis would require almost total recovery of the organic template. But its silica content makes it an interesting candidate for catalytic testing. 

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