الفهرس 
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Abstract
The First chapter includes the literature survey on the reaction of thallium ions (Tl1+, Tl3+) / with an intro.-duction to the polarography equations for determination of the polarographic characterstics / and an introduction to the potentiometric measurements.
The experimental part included the preparation of the stock solutions together with their standarization. It includes also the procedures used for the Polarographic, Potentiometric, and Conductometric measurements.
Chapter three includes the following:
(i) The studies of complex formation between thallic ions and phthalic, fumaric, and maleic acids using potentiometric measurements. The half n value method is used in order to investigate the composition of the complex species and to calculate their formation constants. In each case, one complex with 1:1 metal to ligand is detected. The data of the calculated formation constants show that the stability of Tl(lll) completes is in the order phthalate, maleat, fumarate.
(ii) The conductometric titration studies on the reaction
between thallic ion and phthalic, fumaric, and maleic acids prove the formation of 1:1 and 1:3 (meta1:ligand).
complexes in case of phthalic, fumaric acids, whereas 1:3 in case maleic acid.
Chapter four includes the results of the polarographic behaviour of Tl(III) at the dropping mercury electrode in different concentrations of phthalic, Fumaric and meleic acid as complexing agent and in presence of 0.02M perchloric acid and 0.08M sodium perchlarate as support¬ing electrolyte. The results show that three waves are obtained in presence of fumaric and maleic acids, and two waves in presence of phthalic acid. The first and the second waves are corresponding to the reduction of TI(III) to T1(I) and of Ti(I) to Tl metal respectively. The third wave is due to the reduction of maleic and fumaric acid. The shift in the EL, of two waves increases to more negative potential by increasing the concentration of the acid and the limiting current decreases in the same order. The shifts in EL. and the decreases in the limiting current are attributed to the complex formation between Tl(III) ions and the ligands. The effect of mercury height on the two waves shows that the two waves are controlled by the diffusion of the depolarizer to the electrode surface.
The analysis of the two waves indicates that the electro-reduction of Tl(III) ions at different acid concentration proceeds quasireversibly along the first wave through consumption of two electrons and reversibly along the second wave through consumption of one electron. The polarographic method also is used to investigate the composition of the complex species and to calculate their formation constants. The results indicate that one complex is formed with 1:1 metal to ligand ratio. It is found that the ratios of the stabilities of the oxodized form (Tl (iiI)) and the reduced form (Tl (I)) as log kox are 3.56, 2.571 and 2.55 for phthalate, maleate and fumarate respectively. from these results and potentio-metric data the stability constant of T1(I) is calcu-*-lated it” equals 2.12, 2.35, and 1.86 in the same order.
Chapter Five includes the results of the -polarographic behaviour of Tl(lII) ions in EDTA, acetic acid, monoch-loroacetic acid, and glycine solution at different PH,S. (a) The behaviour in EDTA solutions at different pH’s(4.3-12.6) and different concentration (0.01-0.1M) of EDTA reveals the presence of two waves in all pH’s and EDTA concentrations. In general, the limiting current slightly decreases on increasing EDTA concent¬ration at different pH•s(4.3,8.3). Also E. of the two waves shifts to more negative potentials. The effect of mercury height on the limiting current of the polarographic waves at different EDTA concentrations indicates that the electroreduction process is diffusion controlled along the two waves. Analysis of the polarographic waves of Tl(III) in different pH1s and different concentrations of EDTA indicates that the electrode process along the first wave is quasireversible through consumption of two electrons and along the second wave is reversible through consumption of one electrone in the reduction process.
The effect of Tl(III) ion concentrations at 0.05M, 0.1M EDTA solution at pH 4.3 and 8.3 shows that the EDTA solutions at pH 4.3 and 8.3 can be used in determination of Tl(III).
The electroreduction of Tl(III) ions is investigated in acetic acid solutions at different pH’s (2.3-6.4) and different concentrations of acetic acid (0.1-2.0M) at pH 2.3 and 6.4. Two waves are obtained in all different pH s with e1/2,s shift towards more negative potentials by increasing pH’s and the concentration of the acid. The limiting current of the two waves decreases in the same order. The values of log i/logh plots slopes show that the polarographic waves are controlled by diffusion of the depolarizer. The loganithmic analysis of the two waves indicates that the nature of the reaction process is quasireversible and two electrons are consumed in the reaction process along the first wave. The reaction process is rever¬sible along the second wave with uptake of one electron The effect of Tl(III) ions concentrations at 0.1M and S.OM acetic acid at pH 2.3 and 6.4 shows that the acetic acid solution can be used in the quantitative determination of Tl(III).
)c(The behaviour of Tl(III) in monochloroacetic acid -
solution at different pH,s (1.22-5.0) indicates that the current decreases on increasing either the pH values or the concentration of monochloroacetic acid. The half-wave potential of the two waves slightly shifts to more negative potential. The effect of varying mercury height (h) on the limiting current of the polarographic waves at different pH’ and different monochloroacetic acid concentration indicates that the electroreduction process is mainly diffusion controlled. The logarithmic analysis of the two waves indicates that the nature of the reduction is irrever-ible along the first wave and reversible along the second wave. The effect of Tl(III) concentrations at 0.1M and 2.0M monochloroacetic acid at pH 1.2 2 and 5.0 shows that the monochloroacetic acid is suitable for the quantitative determination of Tl(III).
The electroreduction of Tl(III) in glycine solution at different pH|S (5.0-10.1) and different glycine concen¬trations proceed via two steps.
The shift in the E,1/2 of the two waves increase by increasing either the pH of solution or glycine concentrations. The limiting current decreases in the same order. The effect of mercury height shows that the waves are mainly controlled by diffusion of the depolarizer to the electrode surface. The analysis of the two waves indicates that the electroreduction of Tl(III) at different pH’s and different glycine concentrations proceed quasireversibly along the first wave and reversibly along the second wave. The effect of Tl(III) concentration at 0.3M and 1.0M glycine at pH 5.0 and pH 10.1 shows that glycine solution at pH 5.0 can be used in the deter¬mination of TI(III), whereas at pH 10.1 the deter¬mination of Tl(lII) is only successfull at concentr¬ation ImM Tl(III).
Chapter six includes the results of the polarographic determination of monovalent thallium in EDTA, acetic acid/ monochloroacetic acid and glycine in presence of copper (II), lead (II) and selenium(IV) at different pK,s . a- The polarographic determination of T] (I) in EDTA Solutions i - The interferences reused by Cu(ll) at pH,s 4.2 and 8.2 can be eliminated by SAS viz, Triton-X-100, sod. dodecyl benzene sulphonate, and gelatine, ii- Since the E, of Pb(II) is more negative than that of the Tl (I),addition of SAS is not needed in the determination, of Tl(I) in presence of lead(II). iii- The interferences caused by Se(lV) at pH 4.2 can be eliminated by SAS, whereas selenium(IV) is electroin-active at pH 8.2, accordingly, Tl(I) can be determine in presence of Se(IV) at pH 8.2 without addition of SAS.
Furthermore it is found that by using SAS it is possible to determine T1(I) polar©graphically in - 164 - quaternary mixtures containing Cu(II), Pb(II) and Se(IV) at pH 4.2 and pH 8.2, whereas, T1(I) can be determined in ternary mixtures containing Pb(II) and Se(IV) without addition of SAS at pH 8.2.
The polarographic determination of T1(I) using acetic acid solutions: i - Tne electroreduction of Cu(II) in acetic acid solution at pH 3.2 is represented by a single wave with a’sudden rise in the current. The E, of Cu(II) is more positive than that of T1(I) and the SAS tested has no effect on the Cu(II) reduction wave. Accordingly, Tl(l) can not ”be determined in presence of Cu(II) if the latter is present in a large excess. In alkaline medium (pH 12.2) the determination of •Tl(I) in presence of Cu(II) is impossible due to the precipitation of copper(II) in acetic acid at pH ]2.2. ii - The half wave potential of lead(II) at pH 3.2 is so close to the Et of Tl(I) and the wave of Pb(II) is notaffected by SAS, therefore the determination of T1(I) in presence of Pb(II) at pH 3.2 is impossible. The determination of T1(I) in presence of Pb(II) at Ph 12.2 is possible due to the differences between their E,’ . The E, of Pbillj wave is more negative than, that of Tl (I) . -ii- Thallium(I) can be determined in presence of selenium(IV) at pH 3.2 using SAS to eliminate the two waves of Se(IV) which interfere with the wave of T1(I). However, at pH 12.2, Se(lV) is electron nani-i^o - 165 - therefore/ SAS is not added in this case. Tl(I) can be determined in ternary mixtures contain¬ing Cu(II) and Se(IV) using SAS in acetic acid at pH 3.2 and in ternary mixtures containing Se(IV) and Pb(II) without using SAS in acetic acid at pH 12.2.
- The polarographic determination of Tl(I) in monochloro-acetic acid solutions: i - The half-wave potential of Cu(II) is more positive than that of Tl(I) in monochloroacetic acid at PH 3.1 Thus Tl(l) can not be determined in presence of large amounts of copper(II). At pH 12.1 SAS must be added in the determination of T1(I) to eliminate the wave of Cu(II) which interferes with that of T1(I). ii- It is found that the determination of Tl(l) in
presence of Pb(II) at pH 3.1 is impossible since SAS has no effect on the Pb(II) wave. At pH 12.1 T1(I) can be determined in presence of Pb(TI) without addition of SAS due to the wide differences in the values of their E, iii- By using Triton-X-100/ or gelatine the waves of Se(IV) in monochloroacetic acid at pH 3.1 can be eliminated/ consequently Till) can be determined successfully in presence of Se(IV) in this medium. At pH 12.1 T1(I) can be determined in presence of Se(IV) without using SAS/ since Se(IV) is not reduced in alkaline medium.
Furthermore/ T1(I) can be determined in ternarv - 166 - SAS at pH 3.1, whereas at pH 12.1, T1(I) can be determined in ternary mixtures containing Se(IV) and Pb(II) without addition of SAS. Also, Tl(I) can be determined in quaternary mixtures containing Cu(II) Pb(II) and Se(IV) at pH 12.1 using SAS. The polarographic determination of T1(I) using glycine solutions: i - The determination of T1(I) in presence of Cu(II) at pH 3.2 is possible providing that the concentra¬tion of copper is not present in large amounts. However, at pH 12.2 SAS is added to eliminate the wave of Cu(II) which interferes with that of T1(I). Thallium(I) can be determined in presence of Pb(II) with the addition of SAS at pH 12.2 since the Pb(II) wave is more negative than that of T1(I) at this medium. At PH 3.2, the determination of T1(I) in presence of Pb(II) is impossible due to the inter¬ferences caused by Pb(II) wave even in the presence of SAS .
i- The waves of Se(IV) in glycine solution at pH 3.2 can be eliminated by using SAS. Therefore, the determination of Till) in presence of Se(IV) is im¬possible at pH 3.2. However, T1(I) can be determined in presence of Se(IV) in glycine solution at pH 12.2 without using SAS due to the fact that selenium(IV) is electroinactive in this medium.
from the results obtained it is found that Tl (I) can be determined in quaternary mixtures containing Cu(II), Pb(II) and Se(IV) at pH 12.2 by using SAS.