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Determination of thallium(III) by use of a mercury reductor
Talcma, Vol. 32, No. 12, pp. 1161-I162, 1985 Printed m Great Bntain. All rights reserved
0039-9140/8553.00+ 0.00 CopyrIght Q 1985Pergamon Press Ltd
DETERMINATION OF THALLIUM(III) BY USE OF A MERCURY REDUCTOR S. N. DINDI and N. V. V. S. N. M. SARMA Department of Inorganic and Analytical Chemistry, Andhra University. Waltair. India (Received
12 March 1985. Accepted
9 August 1985)
Summary-A convenient method has been developed for the determination of thallium(lII) by using a mercury reductor. Thallium(II1) is reduced to thallium(I) in 0.5-4N hydrochloric or sulphuric acid medium and the determination is completed by oxidative titration with potassium bromate. The method is extended to analysis of thallium(III~-thallium(I) and thallium(II1 jiron(II1) mixtures.
Among various metal and metal-amalgam reductors, the mercury reductor is one of the most convenient and its use in the determination of iron(HI) vanahexadium(V),3*4 uranium(VI),5.6 antimony(V),’ cyanoferrate(III),2~B molybdenum(V1)’ etc., is well known. All these applications are based on the low redox potential of the mercury(I)/mercury couple in acid media. We have now developed a convenient method for the determination of thallium(II1) by use of a mercury reductor. The method allows determination of both thallium(II1) and thallium(I) in a mixture, by titration of thallium(I) in one aliquot with potassium bromate, lo and of total thallium in a second aliquot after reduction of the thallium(II1) in a mercury reductor. Preliminary studies have shown that iron(H) obtained by reducing iron(II1) in a mercury reductor’ can satisfactorily be titrated with sodium vanadate without interference from thallium(1). Moreover, it has been reported” that a mixture of thallium(I) and iron(I1) can be titrated with potassium bromate to a visual end-point. On the basis of these observations the method has been extended to allow determination of thallium(II1) and iron(III) in a mixture. EXPERIMENTAL
displace the air present, then the reductor is stoppered immediately and shaken vigorously for about 5 min. The supematant solution in the reductor is first decanted into a 250-ml beaker and then filtered into a 500-ml Buchner flask through a G4 filter. The reductor is washed four times (each time with about 20 ml of water and swirling for about 5 set) and the washings are filtered. Finally, the beaker and filter disc are washed twice with 20-ml portions of water and the washings filtered. The hydrochloric acid concentration of the combined filtrate and washings is adjusted to about l.SM, and the solution is titrated with standard potassium bromate solution’0.‘3 (Methyl Orange as indicator). The same determination can also be done in O.-M hydrochloric acid medium, without using sulphuric acid, by the same procedure. The determination can also be accomplished in 0.54M perchloric acid provided there is enough chloride present to remove mercury(I) as mercury(I) chloride. Precision and accuracy. Solutions containing known amounts of thallium(II1) were analysed ten times according to the above procedure. Averages and relative standard deviations were: 131.4 mg, 0.2% (131.3 mg taken) in sulphuric acid medium; 98.9 mg. 0.2% (98.8 mg taken) in hydrochloric acid medium. Inrerferences. Titanium, iron, vanadmm, uranium, antimony, osmium and iridium interfere in this determination. Phosphate and acetate do not interfere up to an overall concentration of 0.08 and 0.25M respectively in the reductor. Any other ions which are either reduced by mercury or oxidized by potassium bromate will interfere. Determination
of thallium(II1)
and thallium(I)
in a mixture
Thallium(II1) solutions, 0.025W.05M were prepared by dissolving thaliium(III) hydroxide” in the desired-acid anh were standardized.“,‘* Thallium(I) solutions (0.025XL05M) in water were prepared from thaii;m(I) chloride or sulphate and standardized.13 Approximately 0.05M sodium vanadate and 0.1 M ferric chloride solutions were prepared and standardized.14.1s A 0.00833M potassium bromate was also prepared and standardized. All other reagents used were of analytical reagent grade.
An aliquot of the mixture IS taken, enough hydrochloric acid is added to give a concentration of about 1.5M on dilution to 100 ml and the thallium(I) IStitrated directly with standard potassium bromate solution. This gives the thallium(1) concentration m the mixture. Another ahquot of the same size is taken and, after reduction of thallium(II1) to thallium(I), titrated with potassium bromate. The difference between the two titrations gives the thalhum(II1) content. Some typical results obtained in sulphuric and hydrochloric acid media are shown in Table 1.
of thallium (III) To an aliquot of thallium(II1) solution placed in a mercury reductor,’ enough sulphuric and hydrochloric acids are added to give an overall sulphuric acid concentration of O.WM and a chloride ion concentration of 0.054.2M on dilution to about 100 ml. Ehloride ion is added to precipitate mercury(I) as Hg#$.] A rapid stream of &bon dioxide is passed into the solution for about 5 min to
of lhallium(III) and iron(III) in a mixture An aliquot of the mixture is placed in the mercury reductor and enough water and concentrated hydrochloric acid are added to give a total volume of about 100 ml of 2M hydrochloric acid. A rapid stream of carbon dioxide is passed into the reductor for about 5 min. then the reductor is stoppered and shaken thoroughly for about 5 min. The supematant solution in the reductor is decanted into a
Reagents
Determination
Determination
1161 TAL
32,IZ-F
1162
SHORT
Table 1. Determination
of thallium(II1) and thallium(I) in a mixture
Taken
Found
Taken
Found
potassium bromate’O solution, after addition of 5 ml of syrupy phosphoric acid, 5 ml of 0.2% copper(I1) sulphate solution and 3 drops of Methyl Orange indicator. The bromate titration volume corresponds to thallium(II1) plus iron(II1). Some representative results are shown in Table 2.
133.1 78.8 45.0 41.9
133.3 78.8 44.5 41.7
42.6 61.7 100.2 38.2
42.8 61.7 99.7 38.2
. _ __ Acknowlec;Igements-We are grateful to Protl L. S. A. Dikshitulu I of our department for his valuable suggestions and to the: UGC, New Delhi, for financial assistance.
53.0 77.0
53.2 76.8
52.1 41.4
51.9 41.1
REFERENCES
Thallium(III), mg Medium
COMMIJNlCATIONS
Thallium(I), mg
1. L. W. McCay and W. T. Anderson, J. Am. Chem. Sot.,
Table 2. Determination Iron(III), mg
of thallium(II1) and iron(II1) in a mixture Thallium(III), mg
Taken
Found
Taken
Found
27.8 30.7 14.0 41.9 33.5 22.3
27.9 30.4 14.1 41.9 33.3 22.1
47.8 44.8 74.6 24.9 39.8 59.7
47.7 44.9 74.9 24.6 40.0 59.7
250-ml beaker and then filtered into a 500-ml conical flask through a Whatman No. 42 filter paper. The mass in the reductor is washed with five 20-ml portions of 0.5M hydrochloric acid, each time with swirling for about 5 sec. Each washing is decanted into the beaker and filtered into the conical flask. The acidity of the solution is adjusted to about l.SM with hydrochloric acid, 5 ml of syrupy phosphoric acid and 3 drops of barium diphenylamine indicator are added and the solution is titrated with standard sodium vanadate. This titration gives the concentration of iron(II1). The procedure is repeated with an identical aliquot of the mixture, but the final solution is titrated with standard
1921, 43, 2372. 2. F. Burriel-Marti, F. L. Conde and S. E. Taccheo, Anal. Chim. Acta, 1953, 9, 293. 3. L. W. McCay and W. T. Anderson, J. Am. Chem. Sot., 1922, 44, 1018. 4. L. S. A. Dikshitulu and D. Satyanarayana, Indian J. Chem., 1974, 12, 180. 5. E. R. Caley and L. B. Rogers, J. Am. Chem. Ser.. 1946, 68, 2202. 6. L. S. A. Dikshitulu and D. Satyanarayana, Z. Anal. Chem., 1974, 271, 366. 7. L. W. McCay, Ind. Eng. Chem., Anal. Ed., 1933, 5, 1. 8. L. S. A. Dikshitulu and D. Satyanarayana, Indian J. Chem., 1976, 14A, 142. 9. N. H. Furman and W. M. Murray, Jr., J. Am. Chem. Sot., 1936, 58, 1689. 10. S. R. Sagi, K. A. Rao and M. S. P. Rao, Indian J. Chem., 1983, 22A, 95. 11. S. R. Sagi and K. V. Ramana, Talanta, 1969, 16, 1217. 12. I. M. Kolthoff and R. Belcher, Volumetric Analysis, Vol. III, p. 370. Interscience, New York, 1957. 13. S. R. Sagi, G. S. P. Raju, K. A. Rao and M. S. P. Rao, Talanra, 1982, 29, 413. 14. G. Gopala Rao and L. S. A. Dikshitulu, Talanta, 1963, 10, 295. 15. A. I. Vogel, A Text Book of Quantitative Inorganic Analysis, 3rd Ed., p. 287. ELBS and Longmans, London, 1968.
0039-9140/8553.00+ 0.00 CopyrIght Q 1985Pergamon Press Ltd
DETERMINATION OF THALLIUM(III) BY USE OF A MERCURY REDUCTOR S. N. DINDI and N. V. V. S. N. M. SARMA Department of Inorganic and Analytical Chemistry, Andhra University. Waltair. India (Received
12 March 1985. Accepted
9 August 1985)
Summary-A convenient method has been developed for the determination of thallium(lII) by using a mercury reductor. Thallium(II1) is reduced to thallium(I) in 0.5-4N hydrochloric or sulphuric acid medium and the determination is completed by oxidative titration with potassium bromate. The method is extended to analysis of thallium(III~-thallium(I) and thallium(II1 jiron(II1) mixtures.
Among various metal and metal-amalgam reductors, the mercury reductor is one of the most convenient and its use in the determination of iron(HI) vanahexadium(V),3*4 uranium(VI),5.6 antimony(V),’ cyanoferrate(III),2~B molybdenum(V1)’ etc., is well known. All these applications are based on the low redox potential of the mercury(I)/mercury couple in acid media. We have now developed a convenient method for the determination of thallium(II1) by use of a mercury reductor. The method allows determination of both thallium(II1) and thallium(I) in a mixture, by titration of thallium(I) in one aliquot with potassium bromate, lo and of total thallium in a second aliquot after reduction of the thallium(II1) in a mercury reductor. Preliminary studies have shown that iron(H) obtained by reducing iron(II1) in a mercury reductor’ can satisfactorily be titrated with sodium vanadate without interference from thallium(1). Moreover, it has been reported” that a mixture of thallium(I) and iron(I1) can be titrated with potassium bromate to a visual end-point. On the basis of these observations the method has been extended to allow determination of thallium(II1) and iron(III) in a mixture. EXPERIMENTAL
displace the air present, then the reductor is stoppered immediately and shaken vigorously for about 5 min. The supematant solution in the reductor is first decanted into a 250-ml beaker and then filtered into a 500-ml Buchner flask through a G4 filter. The reductor is washed four times (each time with about 20 ml of water and swirling for about 5 set) and the washings are filtered. Finally, the beaker and filter disc are washed twice with 20-ml portions of water and the washings filtered. The hydrochloric acid concentration of the combined filtrate and washings is adjusted to about l.SM, and the solution is titrated with standard potassium bromate solution’0.‘3 (Methyl Orange as indicator). The same determination can also be done in O.-M hydrochloric acid medium, without using sulphuric acid, by the same procedure. The determination can also be accomplished in 0.54M perchloric acid provided there is enough chloride present to remove mercury(I) as mercury(I) chloride. Precision and accuracy. Solutions containing known amounts of thallium(II1) were analysed ten times according to the above procedure. Averages and relative standard deviations were: 131.4 mg, 0.2% (131.3 mg taken) in sulphuric acid medium; 98.9 mg. 0.2% (98.8 mg taken) in hydrochloric acid medium. Inrerferences. Titanium, iron, vanadmm, uranium, antimony, osmium and iridium interfere in this determination. Phosphate and acetate do not interfere up to an overall concentration of 0.08 and 0.25M respectively in the reductor. Any other ions which are either reduced by mercury or oxidized by potassium bromate will interfere. Determination
of thallium(II1)
and thallium(I)
in a mixture
Thallium(II1) solutions, 0.025W.05M were prepared by dissolving thaliium(III) hydroxide” in the desired-acid anh were standardized.“,‘* Thallium(I) solutions (0.025XL05M) in water were prepared from thaii;m(I) chloride or sulphate and standardized.13 Approximately 0.05M sodium vanadate and 0.1 M ferric chloride solutions were prepared and standardized.14.1s A 0.00833M potassium bromate was also prepared and standardized. All other reagents used were of analytical reagent grade.
An aliquot of the mixture IS taken, enough hydrochloric acid is added to give a concentration of about 1.5M on dilution to 100 ml and the thallium(I) IStitrated directly with standard potassium bromate solution. This gives the thallium(1) concentration m the mixture. Another ahquot of the same size is taken and, after reduction of thallium(II1) to thallium(I), titrated with potassium bromate. The difference between the two titrations gives the thalhum(II1) content. Some typical results obtained in sulphuric and hydrochloric acid media are shown in Table 1.
of thallium (III) To an aliquot of thallium(II1) solution placed in a mercury reductor,’ enough sulphuric and hydrochloric acids are added to give an overall sulphuric acid concentration of O.WM and a chloride ion concentration of 0.054.2M on dilution to about 100 ml. Ehloride ion is added to precipitate mercury(I) as Hg#$.] A rapid stream of &bon dioxide is passed into the solution for about 5 min to
of lhallium(III) and iron(III) in a mixture An aliquot of the mixture is placed in the mercury reductor and enough water and concentrated hydrochloric acid are added to give a total volume of about 100 ml of 2M hydrochloric acid. A rapid stream of carbon dioxide is passed into the reductor for about 5 min. then the reductor is stoppered and shaken thoroughly for about 5 min. The supematant solution in the reductor is decanted into a
Reagents
Determination
Determination
1161 TAL
32,IZ-F
1162
SHORT
Table 1. Determination
of thallium(II1) and thallium(I) in a mixture
Taken
Found
Taken
Found
potassium bromate’O solution, after addition of 5 ml of syrupy phosphoric acid, 5 ml of 0.2% copper(I1) sulphate solution and 3 drops of Methyl Orange indicator. The bromate titration volume corresponds to thallium(II1) plus iron(II1). Some representative results are shown in Table 2.
133.1 78.8 45.0 41.9
133.3 78.8 44.5 41.7
42.6 61.7 100.2 38.2
42.8 61.7 99.7 38.2
. _ __ Acknowlec;Igements-We are grateful to Protl L. S. A. Dikshitulu I of our department for his valuable suggestions and to the: UGC, New Delhi, for financial assistance.
53.0 77.0
53.2 76.8
52.1 41.4
51.9 41.1
REFERENCES
Thallium(III), mg Medium
COMMIJNlCATIONS
Thallium(I), mg
1. L. W. McCay and W. T. Anderson, J. Am. Chem. Sot.,
Table 2. Determination Iron(III), mg
of thallium(II1) and iron(II1) in a mixture Thallium(III), mg
Taken
Found
Taken
Found
27.8 30.7 14.0 41.9 33.5 22.3
27.9 30.4 14.1 41.9 33.3 22.1
47.8 44.8 74.6 24.9 39.8 59.7
47.7 44.9 74.9 24.6 40.0 59.7
250-ml beaker and then filtered into a 500-ml conical flask through a Whatman No. 42 filter paper. The mass in the reductor is washed with five 20-ml portions of 0.5M hydrochloric acid, each time with swirling for about 5 sec. Each washing is decanted into the beaker and filtered into the conical flask. The acidity of the solution is adjusted to about l.SM with hydrochloric acid, 5 ml of syrupy phosphoric acid and 3 drops of barium diphenylamine indicator are added and the solution is titrated with standard sodium vanadate. This titration gives the concentration of iron(II1). The procedure is repeated with an identical aliquot of the mixture, but the final solution is titrated with standard
1921, 43, 2372. 2. F. Burriel-Marti, F. L. Conde and S. E. Taccheo, Anal. Chim. Acta, 1953, 9, 293. 3. L. W. McCay and W. T. Anderson, J. Am. Chem. Sot., 1922, 44, 1018. 4. L. S. A. Dikshitulu and D. Satyanarayana, Indian J. Chem., 1974, 12, 180. 5. E. R. Caley and L. B. Rogers, J. Am. Chem. Ser.. 1946, 68, 2202. 6. L. S. A. Dikshitulu and D. Satyanarayana, Z. Anal. Chem., 1974, 271, 366. 7. L. W. McCay, Ind. Eng. Chem., Anal. Ed., 1933, 5, 1. 8. L. S. A. Dikshitulu and D. Satyanarayana, Indian J. Chem., 1976, 14A, 142. 9. N. H. Furman and W. M. Murray, Jr., J. Am. Chem. Sot., 1936, 58, 1689. 10. S. R. Sagi, K. A. Rao and M. S. P. Rao, Indian J. Chem., 1983, 22A, 95. 11. S. R. Sagi and K. V. Ramana, Talanta, 1969, 16, 1217. 12. I. M. Kolthoff and R. Belcher, Volumetric Analysis, Vol. III, p. 370. Interscience, New York, 1957. 13. S. R. Sagi, G. S. P. Raju, K. A. Rao and M. S. P. Rao, Talanra, 1982, 29, 413. 14. G. Gopala Rao and L. S. A. Dikshitulu, Talanta, 1963, 10, 295. 15. A. I. Vogel, A Text Book of Quantitative Inorganic Analysis, 3rd Ed., p. 287. ELBS and Longmans, London, 1968.