Weakly basic cationics with amphoterics

This short section is included for the sake of completeness, since it is not likely that this combination will be encountered. 

Mixtures of weakly basic cationics with WW or SW amphoterics can be analysed by titration with SDS in acid solution and BEC in alkaline solution. The measurements obtained are shown in Table 8.2. 

Weak base (C) with WW amphoteric (A) Weak base (C) with SW amphoteric (A) 

Mixtures of weak bases with WS amphoterics (carboxybetaines) can be analysed by the method described in section 7.2.4 [2]. The betaine is determined by potentiometric titration of an initially acid solution in methyl isobutyl ketone with alkali, and the weak base by potentiometric titration of an initially alkaline solution in 50% aqueous propan-2-ol with acid. This procedure distinguishes between tertiary amines and amine oxides (section 7.8). 

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Anionics with weakly basic cationics or amphoterics... 

BEC titration. Most mixtures of anionics with weakly basic cationics or amphoterics can be analysed by BEC titration in acid and alkaline solution. Two-phase titration is more satisfactory than potentiometric. Acid and alkaline have the same meanings as before. The measurements produced are shown in Table 8.3. 

Table 8.3 Titration of mixtures of anionics with weakly basic cationics or amphoterics...

Column 2 strongly basic anion exchanger hydroxide. Retains carboxy-lates and WW and SW amphoterics. Elute with hydrochloric acid. Car boxy lates and amphoterics are eluted rapidly. Response of phosphate esters is uncertain, but if they were not retained by column 1 they would be retained by column 2 and also eluted rapidly. Quaternary salts are converted to the hydroxide, weakly basic cationics (amines, amine oxides) to the free base and betaines to the zwitterionic form. All of these pass through. 

This is more satisfactory for weakly basic cationics than for amphoterics, although the results with WW and WS amphoterics are usually considered reasonable for quality-control purposes. 

The first three form amphoteric oxides and are distinctly superior, as cement-formers, to the latter two which form weakly basic oxides. Data from Table 2.3b indicate that optimum cement formation occurs with cations that have / values lying between 18 and 29. 

Even when modifiers are not necessary for cement formation, they can lead to improved cement properties. Kingery (1950b) also examined this effect. He found that optimum bonding was achieved with cations that had small ionic radii and were amphoteric or weakly basic, such as beryllium, aluminium, magnesium and iron. By contrast, cations that were highly basic and had large ionic radii, for example calcium, thorium and barium, had a detrimental effect on bonding. 

Evaporate both solutions to a low volume, dilute to about 10 ml with water and carry out the indicator test on small portions of each of them in both acid and alkaline solution. The solution from the cation exchange column contains only anionics, soaps, SW and SS sul-phobetaines and nonionics, and the solution from the anion exchange column contains only cationics with both weakly and strongly basic nitrogen, betaines, SS sulphobetaines and nonionics. WW amphoterics are retained by both columns. 

All cations, including weak bases, amine oxides, betaines, amphoterics all bases not sulphobetaines with weakly basic nitrogen... 

Nonionics and WW or amphoterics present. The previous procedure would include all amphoterics with weakly basic nitrogen (WW and SW) in the anionic fraction. If a WW amphoteric is present the simplest procedure is to combine the two columns described, with the cation exchanger first. The WW amphoteric is retained on the cation exchanger and the anionics on the anion exchanger, from which they are eluted as described. 

Nonionics and WW or WS amphoterics present. The previous procedure would include betaines and amphoterics with weakly basic nitrogen in the cationic fraction. 

One might speculate about the anionic, cationic or zwitterionic character of amphoterics with more than one acid or basic group or with both strong and weak acid or basic functions (some of which are commercially available), but there appears to be no published information about their behaviour in ion-exchange columns. If confronted by one of these, it is a simple matter to pass samples through the columns of acidic and basic resins in the acid, base or salt form and see what happens. It should then be straightforward to work out a system for the... 

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