Variable type cations

We learned in Chapter 5 that some metals always form monatomic ions having one given charge in all their compounds. In this book, we will call this type of ion the constant type. Other metals form monatomic ions with different charges (see Figure 5.11). We will call this type the variable type. There are also some polyatomic cations, but only three of these are important for this course. Thus, the first step in naming a cation is to decide which of these three types it is polyatomic, constant type, or variable type. We name them in different ways. 

Naming ions of metals that form ions of more than one charge requires distinguishing between the possibilities. For example, iron forms Fe and Fe ions. We cannot call both of these iron ion because no one would know which of the two we meant. For monatomic cations of variable type, the charge in the form of a Roman numeral is attached to the element s name to indicate which ion we are talking about. For example, Fe is called iron(II) ion and Fe is called iron(lll) ion. This system of nomenclature is called the Stock system. 

Strong acidic cation (SAC) Can exchange all cations and is very useful for all types of water. Has good physical and oxidation stability and provides a variable capacity dependent on regeneration levels. A limitation is the operating efficiency of SAC resins. A relatively low cost resin. 

Qualitatively, the results observed with ferric chloride and lead acetate were highly variable. It was first noted with ferric chloride that gels were forming within the reaction vessel We observed the formation of translucent gels in the reaction vessel with calcium chloride, spermidine and ferric chloride. In the case of lead acetate, a feathery type precipitate formed in the reaction vessel. Macdonald et al. (14) observed formation of a clear gel and flocculated precipitate in high ester pectin treated with lemon endocarp and peel PE isozymes, respectively. They hypothesized that the different gel structures were due to unique mechanism of deesterification by the PE isozymes. Our results with different cations and formation of different gel structure or precipitate seems to be similar to that reported by Macdonald et al. (14). If there is a different mechanism of de-esterification for plant PEs,... 

Soils and vadose zone information, including soil characteristics (type, holding capacity, temperature, biological activity, and engineering properties), soil chemical characteristics (solubility, ion specification, adsorption, leachability, cation exchange capacity, mineral partition coefficient, and chemical and sorptive properties), and vadose zone characteristics (permeability, variability, porosity, moisture content, chemical characteristics, and extent of contamination)... 

It appears that other compounds having this structure type should be possible. In particular, by appropriate substitution of Ba2+ by cations of different charge the MCE count should be variable over some range, and conceivably even compounds having more than 10 MCE per cluster unit might be prepared, with ad-... 

Since all three types of rate-constants are essentially affected by the same factors - although in a different way - it may be useful as a background to the following discussion to specify briefly the principal variables which are now known to affect the phenomenology of any cationic polymerisation these include the following ... 

One of the most signiflcant variables affecting zeolite adsorption properties is the framework structure. Each framework type (e.g., FAU, LTA, MOR) has its own unique topology, cage type (alpha, beta), channel system (one-, two-, three-dimensional), free apertures, preferred cation locations, preferred water adsorption sites and kinetic pore diameter. Some zeolite characteristics are shown in Table 6.4. More detailed information on zeolite framework structures can be found in Breck s book entitled Zeolite Molecular Sieves [21] and in Chapter 2. 

The sample-preparation technique may depend on a number of variables, for example the molecular weight of sample and interferences, the sample volume and analyte concentration, buffer salt (anion and cation) content and metal concentration and type. Other than filtration for particulate removal, most of the approaches are based on the use of chromatographic media for cleaning up samples before analysis. 

When some other factor also enters into the tautomerization equilibrium, such as a variable medium, then tautomerism may be observable over a certain range of medium compositions. Examples of this kind of behaviour may be found in concentrated aqueous acids, where varying degrees of hydration of the two types of cation can lead to a dependence of the tautomeric equilibrium upon the activity of water, as discussed in the preceding section. This happens in the tautomerization of amide and phenol (or anisole) cations and further discussion of this phenomenon will be deferred until later (see pages 333 and 372). 

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