Titration curves, conductometric

In accordance to Kohlrausch s law the electrical conductivity of a solution depends upon the number of ions present and their mobility. For this reason, conductivity measurements can be used to determine the end-points of acid-alkali and other titrations. Present attention is focused on the conductometric titration curves shown in Figures 6.5 (A)-(D). 

Fig. 6.7. Conductometric titration curves of basic components extracted from engine oil CB SAE 30 into glacial acetic acid. Curve 1 -fresh oil, 2 - after 45 h of use, 3 - after 625 h of use (Pawlak et al.,...

Breaks in the conductometric titration curves for the aqueous ZrOCl2-K3-[MoO(OH)(CN)4] system occur at molar ratio 3 2 with the potassium salt as titrant and at 1 1 and 3 2 with ZrOCl2 as titrant corresponding to the formation of KZrO[MoO(OH)(CN)4] and (ZrO)3[MoO(OH)(CN)4]2.292 The e.p.r. spectra of frozen solutions of Zr and Hf peroxo complexes have been analysed.147 The increase in conductivity with decreasing concentration of solutions ofZr02L2 (L = quinoline N-oxide) has been interpreted293 in terms of the equilibrium ... 

Figure 4.7 (a) Conductometric titration curve for the titration of HC1 by NaOH. (b) Conductances of individual ions during the course of the titration summation of these at any volume of titrant corresponds to the point on curve a. 

As far as the determination of the composition of the complex is concerned, this can be obtained from the variation of electrical conductance of an ionic solution titrated with a solution of the neutral receptor as a result of the different mobilities of the species in solution. Plots of molar conductances, Am, against the ratio of the concentrations of the receptor and anion can provide useful information regarding the strength of anion-receptor interaction. In fact, several conclusions can be drawn from the shape of the conductometric titration curves. 

The slope of the conductometric titration curve gives a measure of not only the strength of complexation but also its solvation. If an increase in conductance is observed on complex formation, this may indicate that the anions are highly solvated and therefore less mobile than the complex ion. This behaviour is uncommon but has been previously observed for systems involving lithium and... 

The affinity of the various calix[4]pyrrole receptors (1,2, 8-aa/ / ) for the fluoride anion in acetonitrile at 298.15 K is reflected in the conductometric titration curves of fluoride against the ligand/anion ratio. The data shown in Fig. 4b are in accord with 1H NMR studies which show (Table 1) that the most significant chemical shift changes in the resonances of pyrrole NH and / -CH protons of receptors 1 and 2 were observed upon complexation with the fluoride anion in acetonitrile. 

The enhancement in the receptor capacity to host anions has been successfully achieved by the design of double-cavity ligands. This is reflected in the conductometric titration curve (Fig. 4c) for the fluoride anion when titrated with receptor 7. In fact, in A/,A/-dimethylformamide, this receptor takes up two anions per unit of ligand while discriminating against other spherical (chloride, bromide and iodide) and non-spherical (hydrogen sulphate, perchlorate, nitrate and tri-fluoromethane sulphonate) anions except H2POj. With this anion only the formation of a 1 1 complex was observed. 

Fig. 7.7.1. Conductometric titration curve of a strong acid with a strong base. E designates the end point...

Fig. 7.7.3. Conductometric titration curve of a refiner mechanical pulp made from sulfonated spruce chips (3.47g). End point A corresponds to titration of the sulfonic acid groups and end point B coresponds to titration of the sulfonic and carboxylic acid groups. (Katz et al. 1984)...

Figure 6.19. Conductometric titration curves (a) Titration of strong acid with NaOH. (b) Titration of acetic acid, K, = 1.75 x 10 3 mol dm" with NaOH. (c) Titration of boric acid Jf,= 6x 10" io mol dm" J with NaOH. (d) Titration...

The ligand interchange reaction between metal S-diketonates and edta was utihzed to establish the amount of metal -diketonate by conductometry in DMF or DMSO. The -diketonates studied were of Co(ll), Cu(ll), Mn(ll), Fe(III) and Cr(III). The combination ratios of the metal /3-diketonate with edta were 4 1, 2 1 and 1 1. Presence of less than 1% H2O, inorganic acids or organic solvents did not affect the inflection points in the conductometric titration curves . 

Titration curves for conductometric titrations take a variety of shapes, depending on the chemical system under investigation. In general, they are characterized by straight line portions with dissimilar slopes on either side of the equivalence point, as shown previously in Fig. 3. To establish a conductometric endpoint, after correcting for volume changes, the conductance data are plotted as a function of titrant volume. The two linear portions are then extrapolated, and the point of intersection is taken as the equivalence point. Frequently, reactions fail to proceed to absolute completion, and the conductometric titration curves invariably show departures from strict linearity in the region of the equivalence point. 

The form of the titration curve with cetyl alcohol varied according to the hexadecyltrimethylammonium bromide-cetyl alcohol molar ratio. Figure 2 shows the conductometric titration curves for hexadecyltrimethylammonium bromide-cetyl alcohol ratios of 1 0.33 to 1 6. These curves show that, with increasing proportion of... 

The purpose of this paper is to propose an interpretation of the foregoing results, to develop a mathematical model which uses the capability of the computer to establish the parameters that are important in the emulsification process, to predict the shape of the conductometric titration curves, and, finally, to visualize the conductometric titration curves as three-dimensional conductance-oil volume-cetyl alcohol concentration plots. 

The characteristic conductometric titration curve can be divided into three stages (i) an initial near-linear descending leg... 

The three stages of the conductometric titration curve were expressed as an exponential step function with the requisite parameters. ... 

The actual solute and micellar concentrations of hexadecyltrimethylammonium bromide should be lower than the calculated values because the rodlike particles and micellar aggregates are assumed to be non-conducting. The negative value calculated for the concentration in rodlike particles for the 1 0.33 hexadecyltrimethylammonium bromide-cetyl alcohol molar ratio is essentially zero. Figure 2 shows that the benzene conductometric titration curve for the 1 0.33 hexadecyltrimethylammonium bromide-cetyl alcohol ratio is very close to that for the same concentration of hexa-decyltrimethylammonium bromide without cetyl alcohol (Figure 1). 

Figure 10 shows that varying the hexadecyltrimethylammonium bromide concentration at the same hexadecyltrimethylammonium bromide-cetyl alcohol ratio changed the conductometric titration curve. For 0.4% hexadecyltrimethylammonium bromide at the 1 3 molar ratio, the conductometric titration curve showed no initial descending leg, suggesting that this system contained no emulsifier micelles. In comparison, the conductometric titration curve for 0.6% hexadecyltrimethylammonium bromide-cetyl alcohol at the... 

Figure 11 shows that the conductometric titration curves for 0.6% hexadecyltrimethylammonium bromide were essentially the same for molar ratios of 1 6 and 1 7. In both cases, the absence of a descending leg suggests that no micelles were present. Therefore, a further increase in the cetyl alcohol concentration resulted in an increase of that incorporated into the rodlike particles, which diminishes the crystallinity but gives no significant change in the conductometric titration curve. 

Thus both of these extensions of the changes in the conductometric titration curves resulting from a change in emulsifier and cetyl alcohol concentrations were consistent with the proposed mathematical model. 

The complex variation of the conductance with added oil volume at a given hexadecyltrimethylammonium bromide concentration was shown by a three-dimensional conductance-oil volume-cetyl alcohol concentration plot. The conductometric titration curves of Figure 2 were fitted using various equations. The best fit was obtained with the following expression. 

Table VI gives the values of these thirteen coefficients for the conductometric titration curves of Figure 2 and 0.6% hexadecyltrimethylammonium bromide at molar ratios of 1 0.33, 1 0.50, 1 1, 1 3, and 1 6.

Coefficients of Equation 2 for Conductometric Titration Curves of Figure 2 ... 

The conductometric titration of aqueous hexadecyltrimethyl-ammonium bromide-cetyl alcohol mixtures with benzene allows determination of the mechanism of emulsification. However, the shapes of the conductometric titration curves are complex the most sta-... 

Figure 15. Three-dimensional plot of family of conductometric titration curves calculated using Equation 2 for titration at 63°C of 25 cc water containing 0.15 g hexadecyltrimethylammonium bromide and varying concentrations of cetyl alcohol with benzene at a constant rate of Icc/min viewed at a horizontal angle of 275° and a vertical angle of 50°.

A typical conductometric titration curve for a DEAE cellulose anion exchanger of 2.68% N is shown in (Fig. 7). 

Figure 7. Conductometric titration curve of a 0.5001 g sample of DEAE cellulose of 2.58% N (0.92 meq) in base form in presence of 1.802 meq HCl vs. standardized 1.0 M NaOH. XY is neutralization of excess HCl YZ represents exchange of CT ions of exchanger for Off ions.

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