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Potentiometric Titrations with Anti- Table l+-Results of ...
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Indian Journal of Chemistry Vol. 23A, May 1984, p: 448 Potentiometric Titrations with Anti- mony (V) Chloride in Non-aqueous Medium A V NAIDU, C V RAJESWARI & P R NAIDU· Department of Chemistry, Sri Venkateswara University, College of Engineering, Tirupa ti 517 502 Received 29 July 1983; revised and accepted 29 December 1983 Antimony (V) chloride in methyl ethyl ketone medium has been used as a titrant for the potentiometric determination of urotropine (hexamine), 3-picoline, dibutylamine, cyclohexylamine, pyrrolidine, 4-aminopyridine, and piperidine. The results show that semimicro quantities of the nitrogen bases can be determined accurately employing antimony (V) chloride as a titrant. A survey of the literature shows that the Lewis acids have been used only to a limited extent as titrants in non-aqueous media 1-5. The present work has been taken up to study the use of antimony (V) chloride as a titrant for the determination of nitrogen bases such as urotropine (hexamine), 3-picoline, dibutylamine, cyclohexylamine, pyrrolidine, 4-aminopyridine and piperidine in non-aqueous media. Potentiometric determination of hexamine with antimony (V) chloride was carried out in three commonly used solvents, namely, acetic acid, chloroform and methyl ethyl ketone (M EK). ME K has been found to be the best solvent because it gives the best potential jump, dissolves a wide variety of materials, is sufficiently weakly acidic to permit the titration of very weak acids and is sufficiently weakly basic to be good differentiating solvent as reported by Harlow et al,", Hence MEK was chosen as the solvent for all further titrations. All the reagents used were of AR grade. The solvent MEK was dried over anhydrous potassium carbonate for 24 hr and then distilled using a fractionating column. The liquid bases were purified by standard methods 7. The purities of the solvent and the liquid bases were checked by comparing the measured densities (using a bicapillary pycnometer reported by Naidu and Krishnan'') with those reported in literature. The purity of the solid bases was ascertained by their melting points. A stock solution of antimony (V) chloride (I M) was prepared by mixing ice-cooled antimony (V) chloride (7 ml) with the ice-cooled MEK (50 ml). The stock solution was further diluted with the solvent to obtain a solution of desired concentration. The acid solution was standardised potentiometrically using a standard solution of sodium acetate. The sodium acetate solution was prepared by dissolving an accurately weighed quantity of the salt in the minimum quantity 448 Table l+-Results of Potentiometric Titration of Some Nitrogen Bases Against Antimony (V) Chloride Base Amount (mg) Difference Taken Found (mg) Urotropine 59.05 29.52 54.26 27.13 38.24 19.12 35.33 17.66 38.08 19.04 41.74 20.86 48.33 23.96 58.43 29.54 54.00 27.22 38.59 19.44 35.00 17.52 37.37 19.14 42.12 20.81 48.42 24.16 -0.62 0.02 -0.26 0.09 0.35 0.32 -0.33 -0.14 -0.71 0.10 0.35 -0.05 0.09 0.20 3-Picoline Dibutylamine Cyciohexylamine Pyrolidine 4-Aminopyridine Piperidine of acetic acid as the salt was not freely soluble in MEK, and then it was diluted with MEK. The presence of small amounts of acetic acid did not interfere with the titration". Weighed samples of the bases were dissolved directly in the solvent. The end point was located potentiometrically using an Elico digital pH -rneter fitted with a glass-saturated calomel electrode assembly. The volume of the titrant crresponding to the end point was determined by the calculation method 10. In all the cases the base to acid mole ratio was found to be I: I. The titration results are presented in Table I. The results of the investigation show that solution of nitrogen bases of the order of I x 1 -2 M can be successfully titrated with antimony (V) chloride with an accuracy of ±2% in non-aqueous medium. The accuracy of the results presented here parallels that observed using chlorosulphonic acid as a titrant 1. References I Peterson W S. Heimerzheim C J & Smith G B L. J .4m chem Soc. 65 (1943) 2403. 2 Hitchcock ET & Elving P J. Analytica Chim Acta. 27 (1962) 501. 3 Paul R C & Vashist J L, Indian J Chem, 7 (1969) 1243. 4 Paul R C. Sing P & Chadha S C. Indian J Chern, 8 (1970) 1010. 5 Naidu P R. Mohan Rao K C. Reddy N S & Naidu P B. Curr Sci, 46 (1977) 520. 6 Harlow G A. Noble eM & Garrard E A Wyld, Analyt Chem, 28 (1956) 787. 7 Riddick 1A & Bunger W B, Organic so/;,ents(Wiley Interscience, New York). 1970. 8 Naidu PR & Krishnan V R. Trans Faraday Sac, 61 (1965) 1347. 9 Mohan Rao K C & Naidu P R. Proc Indian A cad S 7 A (1971) 7. 10 Lingane 1 1. Electroanalytical chemistry (In, .science Publishers. New York). 1966. II Mohan Rao K C & Naidu P R. Talanta, 19 (1972) 1465.
Transcript of Potentiometric Titrations with Anti- Table l+-Results of ...
Indian Journal of ChemistryVol. 23A, May 1984, p: 448
Potentiometric Titrations with Anti-mony (V) Chloride in Non-aqueous Medium
A V NAIDU, C V RAJESWARI & P R NAIDU·
Department of Chemistry, Sri Venkateswara University,College of Engineering, Tirupa ti 517 502
Received 29 July 1983; revised and accepted 29 December 1983
Antimony (V) chloride in methyl ethyl ketone medium has beenused as a titrant for the potentiometric determination of urotropine(hexamine), 3-picoline, dibutylamine, cyclohexylamine, pyrrolidine,4-aminopyridine, and piperidine. The results show thatsemimicro quantities of the nitrogen bases can be determinedaccurately employing antimony (V) chloride as a titrant.
A survey of the literature shows that the Lewis acidshave been used only to a limited extent as titrants innon-aqueous media 1-5. The present work has beentaken up to study the use of antimony (V)chloride as atitrant for the determination of nitrogen bases such asurotropine (hexamine), 3-picoline, dibutylamine,cyclohexylamine, pyrrolidine, 4-aminopyridine andpiperidine in non-aqueous media.
Potentiometric determination of hexamine withantimony (V) chloride was carried out in threecommonly used solvents, namely, acetic acid,chloroform and methyl ethyl ketone (M EK). ME K hasbeen found to be the best solvent because it gives thebest potential jump, dissolves a wide variety ofmaterials, is sufficiently weakly acidic to permit thetitration of very weak acids and is sufficiently weaklybasic to be good differentiating solvent as reported byHarlow et al,", Hence MEK was chosen as the solventfor all further titrations.
All the reagents used were of AR grade. The solventMEK was dried over anhydrous potassium carbonatefor 24 hr and then distilled using a fractionatingcolumn. The liquid bases were purified by standardmethods 7. The purities of the solvent and the liquidbases were checked by comparing the measureddensities (using a bicapillary pycnometer reported byNaidu and Krishnan'') with those reported inliterature. The purity of the solid bases was ascertainedby their melting points.
A stock solution of antimony (V) chloride (I M) wasprepared by mixing ice-cooled antimony (V) chloride(7 ml) with the ice-cooled MEK (50 ml). The stocksolution was further diluted with the solvent to obtaina solution of desired concentration. The acid solutionwas standardised potentiometrically using a standardsolution of sodium acetate. The sodium acetatesolution was prepared by dissolving an accuratelyweighed quantity of the salt in the minimum quantity
448
Table l+-Results of Potentiometric Titration of SomeNitrogen Bases Against Antimony (V) Chloride
Base Amount (mg) Difference
Taken Found (mg)
Urotropine 59.0529.5254.2627.1338.2419.1235.3317.6638.0819.0441.7420.8648.3323.96
58.4329.5454.0027.2238.5919.4435.0017.5237.3719.1442.1220.8148.4224.16
-0.620.02
-0.260.090.350.32
-0.33-0.14-0.71
0.100.35
-0.050.090.20
3-Picoline
Dibutylamine
Cyciohexylamine
Pyrolidine
4-Aminopyridine
Piperidine
of acetic acid as the salt was not freely soluble in MEK,and then it was diluted with MEK. The presence ofsmall amounts of acetic acid did not interfere with thetitration". Weighed samples of the bases weredissolved directly in the solvent.
The end point was located potentiometrically usingan Elico digital pH -rneter fitted with a glass-saturatedcalomel electrode assembly. The volume of the titrantcrresponding to the end point was determined by thecalculation method 10. In all the cases the base to acidmole ratio was found to be I: I.
The titration results are presented in Table I. Theresults of the investigation show that solution ofnitrogen bases of the order of I x 1 -2 M can besuccessfully titrated with antimony (V) chloride withan accuracy of ±2% in non-aqueous medium. Theaccuracy of the results presented here parallels thatobserved using chlorosulphonic acid as a titrant 1 .
ReferencesI Peterson W S. Heimerzheim C J & Smith G B L. J .4m chem Soc.
65 (1943) 2403.2 Hitchcock E T & Elving P J. Analytica Chim Acta. 27 (1962) 501.3 Paul R C & Vashist J L, Indian J Chem, 7 (1969) 1243.4 Paul R C. Sing P & Chadha S C. Indian J Chern, 8 (1970) 1010.5 Naidu P R. Mohan Rao K C. Reddy N S & Naidu P B. Curr Sci,
46 (1977) 520.6 Harlow G A. Noble eM & Garrard E A Wyld, Analyt Chem, 28
(1956) 787.7 Riddick 1 A & Bunger W B, Organic so/;,ents(Wiley Interscience,
New York). 1970.8 Naidu P R & Krishnan V R. Trans Faraday Sac, 61 (1965) 1347.9 Mohan Rao K C & Naidu P R. Proc Indian A cad S 7 A (1971)
7.10 Lingane 1 1. Electroanalytical chemistry (In, .science
Publishers. New York). 1966.II Mohan Rao K C & Naidu P R. Talanta, 19 (1972) 1465.
