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Determination of sulphur monochloride by oxidation with chloramine-T
Short communications
295
REFERENCES 1 P. Wehber and W. Z. Johannsen, Z. analyt. Chem., 1957,158,7. 1 R. Belcher, T. V. Ramakrishna and T. S. West, Talanta, 1962, 9, 943. * I. P. Alimarin and Si-i Khan, Zhur. analit. Khim., 1963, 18, 182. 4 S. V. Elinson and L. I. Pobedina, ibid., 1963, 18, 189. e R. Belcher, T. V. Ramakrishna and T. S. West, 7’alanta,1963,10, 1013. DF. H. Pollard, P. Hanson and W. J. Geary, Awlyt. Chim. Acta, 1959, 20,26. 7A. I. Busev and V. M. Ivanov, Vestnik.Moskov. Univ., 1960, Ser. II Khim. 15, No. 3, 52. BK. L. Cheng, Talunta, 1962,9,739. o T. M. Florence and Y. Farrar, Ancdyt. Chem., 1963,35, 1613. lo A. I. Busev and V. M. Ivanov, Zhur. analit. Khim., 1963,18,208. I1 Idem, best. Vysshikh Uchebn. Zavedenii, Khim. i Khim. Tekhnol., 1961, 4, 914. la A, I. Busev and F. Chang, Vestnik Moskov, Univ., 1960, Ser. II Khim. 15, No. 6, 46. I* Zdem, T&mm, 1962, 9, 101. I4 L. Sommer and M. Hnilickova, Anulyt. Chim. Acta, 1962,27, 241. l6 K. Hagiwara and I. Muraki, Japan Analyst, 1961,10, 1022. I6 P. P. Kish and S. T. Orlovsky, Zhur. analit. Khim., 1962,17, 1057. l7 K. Hagiwara, M. Nakane, Y. Osumy, E. Ishii and Y. Miyake, JU~UJJAnalyst, 1961, 10, 1373. la M. HniliEkova and L. Sommer, Z. unalyt. Chem., 1963,193,171. l* A. I. Busev and V. M. Ivanov, Zhur. analit. Khim., 1964, 19,232. so P, Job, Ann. Chim. Phys., 1928,9, 113. *i I. Ostromyslensky, Ber., 1911, 44, 268. ‘* J. H. Yoe and A. L. Jones, Znd. Eng. Chem., Analyt., 1944,16, 111. L8A. E. Harvey and D. L. Manning, J. Amer. Chem. Sot., 1950,72,4488. adE. B. Sandell, Calorimetric Determination of Truces of Metals. Interscience Publishers, New York, 3rd Ed., 1959,925 p. t6 G. Charlot, Dosages Colorimetriques des Elements Mineranx. Masson, Paris, 2nd Ed., 1961, p. 357. I@J. JanouSek, Coil. Czech. Chem. Comm., 1962, 27,2972. *’ F. W. Staten and E. W. D. Huffen, Analyt. Chem., 1959, 31, 2003. *B0. Budevsky and R. Piibil, Talantu, 1964, 11, 1313.
Determination of sulplmr monochloride by oxidation with chloramine-T (Received 5 November 1964. Accepted 21 December 1964) INVESTIGATIONS carried out by the present authors showed that a solution of sulphur monochloride in dioxan could be oxidised by an excess of acidified chloramine-T solution. The sulphur present in sulphur chloride is quantitatively converted to sulphuric acid. A rapid and an elegant method for the determination of sulphur chloride has been evolved and it is described in this communication.
Reagents Chlorumine-T. About 15 g of a recrystallised sample of pure chloramine-T were dissolved in 1 litre of water and stocked in an amber coloured bottle. The solution was standardised iodometritally in an acidic medium as described earlier.ls* Sulphur chloride. A sample of sulphur monochloride was treated with 10% of its weight of active charcoal and of pure sulphur; this was refluxed on a water-bath in an all-glass apparatus, then distilled under reduced pressure (28 mm at 41”)” The middle fraction of the distillate was collected and preserved in sealed tubes. A solution of such a sample (6 %) in carbon tetrachloride was analysed by two methods. The sulphur content was determined by the mercury decomposition method’ described by Rao and Rao and the chlorine was determined bv the sulohur iodide method described bv Rao.6 The analytical results indicated that the purity of the sulphur chloride was at least 99*9%‘and that the atomic ratio sulphur :chlorine was 1: 1. A solution of sulphur chloride in pure dry dioxan (6 %) also gave the same result. Procedure An aliquot of the sulphur chloride solution in dioxan (5 ml) was added to a known excess of acidified chloramine-T solution (50 ml of chloramine-T with 25 ml of 2M HCl and 10-25 ml of dioxan in a stoppered conical flask). The reactants in the flask were well shaken and set aside for
296
Short communications
about 0.5 hr. At the end of this period 30 ml of 10% potassium iodide solution were added, and the liberated iodine was titrated agamst standard thiosulphate solution (0-W). The amount of chloramiue-T consumed by sulphur chloride was then obtained from the titre, and the number of equivalents of the oxidant required per mole of sulphur chloride was calculated. No blank correction was found to be necessary, the blank being less that @05 ml equivalent of thiosul hate. The analytical values were found to be reproducible and the results of a Few representative experiments are given in Table I. TABLEI.--OXIDATION
OF SULPHUR
MONOCHLORIDE
WlTH
CHLORAMINE-T
-
Expt. no. 1. 2. ::
Sulphur chloride taken, moles x RP -1.38 5.69 6.89 Il.38 14.22 28.50
Chloramine-T consumed, quits X lo” 13.83 56.87 68.65 113.80 142.70 28440
Chloramine-T consumed per mole of sulphur monochloride, quills
10-02 9.99 9.96 1000 10.03 9.98
RESULTS AND DISCUSSIONS It can be seen from the results in Table I that 10 equivalents of chloramine-T are consumed by 1 mole of sulphur chloride, as would be expected stoichiometrically from the equation SIClp + 8 HpO + 10 e -+ 2SO,*- + 2Cl- + 16H+. It was found advantageous to employ a 7 to I-fold excess of the oxidant over the stoichiometric requirement of the equation.* It is better to add some dioxan to the oxidant before adding the dloxan solution of sulphur chloride. Solutions of sulphur chloride in carbon tetrachloride were found to consume large quantities of chloramine-T even when the solution was homogenised for purposes of oxidation by the addition of dioxan or alcohol. Such solutions in carbon tetrachloride are, therefore, not suitable for this purpose. D. K. PADMA A. R. VASIJLWVA MURTHY Department of Inorganic and Physicd Chemistry Zndiax institute of Science -alore-12, India Sunuuary_-A rapid method is described for the determination of sulphur monochloride by adding excess of chloramine-T and determining the excess iodometrically. Zasammeufassuug-Eine Schnellmethode xur Restimmung von Schwefelmonochlorid wird beschrieben. Es wird mit einem Uberschut3 Chloramin T oxydiert und der UberschulJ mit Jodid und Thiosulfat bestimmt. Rkuue-On d&it une m6thode de dosage du monochlorure de soufre par addition dun exds de chloramine T et dosage de l’exc&s par l’iode et l’hyposulfite. + The products of the hydrolysis of sulphur chloride are very varied, including in the present reaction, sulphide, sulphite, thiosul hate, polythiofate and elemental sulphur. In the present determination, if the solution of suYphur chloride IS concentrated, there IS a possibility of the separation of appreciable amounts of elemental sulphur, and this is then d&cult to oxidisc further b the chloramine-T. Therefore, a large excess of oxidant is recommended. If the sulphur cK_1 oride solution is dilute, as little as 30 % in excess is sufficient.
Short communications
297
REFERENCES 1 A. R. Vasudeva Murthy and B. Sanjiva Rao, Proc. Indian Acad. Sci., 1952,35A, 7. 1 E. Bishop and V. J. Jennings, Talanra, 1958,1,197. * B. Sanjiva Rao, Proc. Indian Acad. Sot., 1939,10,423. ’ B. Sanjiva Rao and M. R. A. R,ao, 10th ZnternaIional Congress of Ckernistry, 1938,3,462. 6 M. R. A. Rao, Proc. Indian Acod. Sci., 1940,11,162.
Precipitation of lead sulphate from homogeneous solution by hydrolysis of snlphamic acid (Received 10 June 1964. Accepted 6 December 1964)
THEtechnique and advantages of precipitation from homogeneous solution have been amply presented by Gordon, Salutsky and Willard.’ They also reviewed the methods that have been employed to generate sulphate ions for the determination of barium, calcium, strontium and lead. Elving and Zook’ precipitated lead sulphate by hydrolysis of dimethyl sulphate in 70-80x methanol. Satisfactory accuracy and precision were obtained for amounts of lead in the range of 10 to 100 mg, except in the presence of large amounts of iron(II1) and aluminium(II1). The conditions under which small quantities of lead are precipitated arc somewhat stringent. The concentration of the methanol, amount of dimethyl sulphate added and digestion t‘ime required are dependent upon the quantities of lead and foreign ions present. There is also a tendency for the precipitate to “creep.” Jamagin and Kenneth precipitated lead sulphate by hydrolysis of sulphamic acid catalyzed by the presence of potassium chlorate. A small-sized, uniform precipitate was formed, the volume of which was measured after centrifugation. The successful use of the hydrol sis of sulphamic acid for the precipitation of barium sulphate *s6led to the present investigation oP the precipitation of lead sulphate by a similar procedure. EXPERIMENTAL All reagents met American Chemical Society specifications of purity. Stdek solutions of lead nitrate. Prepared by dissolving the reagent in distilled water. Definite, volumes of these solutions, measured by means of pipettes, were used in subsequent analyses. The quantity of lead present in the solution delivered by a given pipette was determined by evaporating the solution with an excess of sulphuric acid in a platinum dish. The lead sulphate thus obtained was ignited to constant weight in an electric muflle furnace at 550-600”. Stock solutions of possible interfering ions were prepared by dissolving the corresponding salts in distilled water. National Bureau of Standards copper-base alloys were aqalysed to check the analytical procedure. Apparatus Filtering media. Both porcelain filtering crucibles (Coors, fine porosity) and filter paper were used
successfully for the filtration. Some difficulty was encountered in bringing the porous porcelain crucibles to constant weight if the excess sulphuric acid solution was not removed by a final wash with ethyl alcohol. With either medium, the precipitate was ignited to constant weight in-an electric muffle furnace at 550-600”. Preliminary experiments
Preliminary tests were made to determine the optimum conditions necessary to effect complete precipitation of the lead sulphate. For these tests, 25 ml of lead nitrate stock solution containing approximately 100 mg of lead ion were ipetted into 250-ml beakers. A weighed portion of reagent grade sulphamic acid and suIEcient disti Eed water to give a solution volume of 100 ml were added to each sample. These solutions were heated to incipient boiling for varying times up to 2 hr. Portions of the supematant liquid were tested for completeness of precipitation by adding dilute sulphuric acid. Optimum conditions were obtained when 2 g of sulphamic acid were added to the solutions and the period of heating was 1 hr. The use of O-5- and l-g portions of sulphamic acid gave results which were sli htly low. The heating time and temperature were more critical than the amount of sulphamic acl*d.
295
REFERENCES 1 P. Wehber and W. Z. Johannsen, Z. analyt. Chem., 1957,158,7. 1 R. Belcher, T. V. Ramakrishna and T. S. West, Talanta, 1962, 9, 943. * I. P. Alimarin and Si-i Khan, Zhur. analit. Khim., 1963, 18, 182. 4 S. V. Elinson and L. I. Pobedina, ibid., 1963, 18, 189. e R. Belcher, T. V. Ramakrishna and T. S. West, 7’alanta,1963,10, 1013. DF. H. Pollard, P. Hanson and W. J. Geary, Awlyt. Chim. Acta, 1959, 20,26. 7A. I. Busev and V. M. Ivanov, Vestnik.Moskov. Univ., 1960, Ser. II Khim. 15, No. 3, 52. BK. L. Cheng, Talunta, 1962,9,739. o T. M. Florence and Y. Farrar, Ancdyt. Chem., 1963,35, 1613. lo A. I. Busev and V. M. Ivanov, Zhur. analit. Khim., 1963,18,208. I1 Idem, best. Vysshikh Uchebn. Zavedenii, Khim. i Khim. Tekhnol., 1961, 4, 914. la A, I. Busev and F. Chang, Vestnik Moskov, Univ., 1960, Ser. II Khim. 15, No. 6, 46. I* Zdem, T&mm, 1962, 9, 101. I4 L. Sommer and M. Hnilickova, Anulyt. Chim. Acta, 1962,27, 241. l6 K. Hagiwara and I. Muraki, Japan Analyst, 1961,10, 1022. I6 P. P. Kish and S. T. Orlovsky, Zhur. analit. Khim., 1962,17, 1057. l7 K. Hagiwara, M. Nakane, Y. Osumy, E. Ishii and Y. Miyake, JU~UJJAnalyst, 1961, 10, 1373. la M. HniliEkova and L. Sommer, Z. unalyt. Chem., 1963,193,171. l* A. I. Busev and V. M. Ivanov, Zhur. analit. Khim., 1964, 19,232. so P, Job, Ann. Chim. Phys., 1928,9, 113. *i I. Ostromyslensky, Ber., 1911, 44, 268. ‘* J. H. Yoe and A. L. Jones, Znd. Eng. Chem., Analyt., 1944,16, 111. L8A. E. Harvey and D. L. Manning, J. Amer. Chem. Sot., 1950,72,4488. adE. B. Sandell, Calorimetric Determination of Truces of Metals. Interscience Publishers, New York, 3rd Ed., 1959,925 p. t6 G. Charlot, Dosages Colorimetriques des Elements Mineranx. Masson, Paris, 2nd Ed., 1961, p. 357. I@J. JanouSek, Coil. Czech. Chem. Comm., 1962, 27,2972. *’ F. W. Staten and E. W. D. Huffen, Analyt. Chem., 1959, 31, 2003. *B0. Budevsky and R. Piibil, Talantu, 1964, 11, 1313.
Determination of sulplmr monochloride by oxidation with chloramine-T (Received 5 November 1964. Accepted 21 December 1964) INVESTIGATIONS carried out by the present authors showed that a solution of sulphur monochloride in dioxan could be oxidised by an excess of acidified chloramine-T solution. The sulphur present in sulphur chloride is quantitatively converted to sulphuric acid. A rapid and an elegant method for the determination of sulphur chloride has been evolved and it is described in this communication.
Reagents Chlorumine-T. About 15 g of a recrystallised sample of pure chloramine-T were dissolved in 1 litre of water and stocked in an amber coloured bottle. The solution was standardised iodometritally in an acidic medium as described earlier.ls* Sulphur chloride. A sample of sulphur monochloride was treated with 10% of its weight of active charcoal and of pure sulphur; this was refluxed on a water-bath in an all-glass apparatus, then distilled under reduced pressure (28 mm at 41”)” The middle fraction of the distillate was collected and preserved in sealed tubes. A solution of such a sample (6 %) in carbon tetrachloride was analysed by two methods. The sulphur content was determined by the mercury decomposition method’ described by Rao and Rao and the chlorine was determined bv the sulohur iodide method described bv Rao.6 The analytical results indicated that the purity of the sulphur chloride was at least 99*9%‘and that the atomic ratio sulphur :chlorine was 1: 1. A solution of sulphur chloride in pure dry dioxan (6 %) also gave the same result. Procedure An aliquot of the sulphur chloride solution in dioxan (5 ml) was added to a known excess of acidified chloramine-T solution (50 ml of chloramine-T with 25 ml of 2M HCl and 10-25 ml of dioxan in a stoppered conical flask). The reactants in the flask were well shaken and set aside for
296
Short communications
about 0.5 hr. At the end of this period 30 ml of 10% potassium iodide solution were added, and the liberated iodine was titrated agamst standard thiosulphate solution (0-W). The amount of chloramiue-T consumed by sulphur chloride was then obtained from the titre, and the number of equivalents of the oxidant required per mole of sulphur chloride was calculated. No blank correction was found to be necessary, the blank being less that @05 ml equivalent of thiosul hate. The analytical values were found to be reproducible and the results of a Few representative experiments are given in Table I. TABLEI.--OXIDATION
OF SULPHUR
MONOCHLORIDE
WlTH
CHLORAMINE-T
-
Expt. no. 1. 2. ::
Sulphur chloride taken, moles x RP -1.38 5.69 6.89 Il.38 14.22 28.50
Chloramine-T consumed, quits X lo” 13.83 56.87 68.65 113.80 142.70 28440
Chloramine-T consumed per mole of sulphur monochloride, quills
10-02 9.99 9.96 1000 10.03 9.98
RESULTS AND DISCUSSIONS It can be seen from the results in Table I that 10 equivalents of chloramine-T are consumed by 1 mole of sulphur chloride, as would be expected stoichiometrically from the equation SIClp + 8 HpO + 10 e -+ 2SO,*- + 2Cl- + 16H+. It was found advantageous to employ a 7 to I-fold excess of the oxidant over the stoichiometric requirement of the equation.* It is better to add some dioxan to the oxidant before adding the dloxan solution of sulphur chloride. Solutions of sulphur chloride in carbon tetrachloride were found to consume large quantities of chloramine-T even when the solution was homogenised for purposes of oxidation by the addition of dioxan or alcohol. Such solutions in carbon tetrachloride are, therefore, not suitable for this purpose. D. K. PADMA A. R. VASIJLWVA MURTHY Department of Inorganic and Physicd Chemistry Zndiax institute of Science -alore-12, India Sunuuary_-A rapid method is described for the determination of sulphur monochloride by adding excess of chloramine-T and determining the excess iodometrically. Zasammeufassuug-Eine Schnellmethode xur Restimmung von Schwefelmonochlorid wird beschrieben. Es wird mit einem Uberschut3 Chloramin T oxydiert und der UberschulJ mit Jodid und Thiosulfat bestimmt. Rkuue-On d&it une m6thode de dosage du monochlorure de soufre par addition dun exds de chloramine T et dosage de l’exc&s par l’iode et l’hyposulfite. + The products of the hydrolysis of sulphur chloride are very varied, including in the present reaction, sulphide, sulphite, thiosul hate, polythiofate and elemental sulphur. In the present determination, if the solution of suYphur chloride IS concentrated, there IS a possibility of the separation of appreciable amounts of elemental sulphur, and this is then d&cult to oxidisc further b the chloramine-T. Therefore, a large excess of oxidant is recommended. If the sulphur cK_1 oride solution is dilute, as little as 30 % in excess is sufficient.
Short communications
297
REFERENCES 1 A. R. Vasudeva Murthy and B. Sanjiva Rao, Proc. Indian Acad. Sci., 1952,35A, 7. 1 E. Bishop and V. J. Jennings, Talanra, 1958,1,197. * B. Sanjiva Rao, Proc. Indian Acad. Sot., 1939,10,423. ’ B. Sanjiva Rao and M. R. A. R,ao, 10th ZnternaIional Congress of Ckernistry, 1938,3,462. 6 M. R. A. Rao, Proc. Indian Acod. Sci., 1940,11,162.
Precipitation of lead sulphate from homogeneous solution by hydrolysis of snlphamic acid (Received 10 June 1964. Accepted 6 December 1964)
THEtechnique and advantages of precipitation from homogeneous solution have been amply presented by Gordon, Salutsky and Willard.’ They also reviewed the methods that have been employed to generate sulphate ions for the determination of barium, calcium, strontium and lead. Elving and Zook’ precipitated lead sulphate by hydrolysis of dimethyl sulphate in 70-80x methanol. Satisfactory accuracy and precision were obtained for amounts of lead in the range of 10 to 100 mg, except in the presence of large amounts of iron(II1) and aluminium(II1). The conditions under which small quantities of lead are precipitated arc somewhat stringent. The concentration of the methanol, amount of dimethyl sulphate added and digestion t‘ime required are dependent upon the quantities of lead and foreign ions present. There is also a tendency for the precipitate to “creep.” Jamagin and Kenneth precipitated lead sulphate by hydrolysis of sulphamic acid catalyzed by the presence of potassium chlorate. A small-sized, uniform precipitate was formed, the volume of which was measured after centrifugation. The successful use of the hydrol sis of sulphamic acid for the precipitation of barium sulphate *s6led to the present investigation oP the precipitation of lead sulphate by a similar procedure. EXPERIMENTAL All reagents met American Chemical Society specifications of purity. Stdek solutions of lead nitrate. Prepared by dissolving the reagent in distilled water. Definite, volumes of these solutions, measured by means of pipettes, were used in subsequent analyses. The quantity of lead present in the solution delivered by a given pipette was determined by evaporating the solution with an excess of sulphuric acid in a platinum dish. The lead sulphate thus obtained was ignited to constant weight in an electric muflle furnace at 550-600”. Stock solutions of possible interfering ions were prepared by dissolving the corresponding salts in distilled water. National Bureau of Standards copper-base alloys were aqalysed to check the analytical procedure. Apparatus Filtering media. Both porcelain filtering crucibles (Coors, fine porosity) and filter paper were used
successfully for the filtration. Some difficulty was encountered in bringing the porous porcelain crucibles to constant weight if the excess sulphuric acid solution was not removed by a final wash with ethyl alcohol. With either medium, the precipitate was ignited to constant weight in-an electric muffle furnace at 550-600”. Preliminary experiments
Preliminary tests were made to determine the optimum conditions necessary to effect complete precipitation of the lead sulphate. For these tests, 25 ml of lead nitrate stock solution containing approximately 100 mg of lead ion were ipetted into 250-ml beakers. A weighed portion of reagent grade sulphamic acid and suIEcient disti Eed water to give a solution volume of 100 ml were added to each sample. These solutions were heated to incipient boiling for varying times up to 2 hr. Portions of the supematant liquid were tested for completeness of precipitation by adding dilute sulphuric acid. Optimum conditions were obtained when 2 g of sulphamic acid were added to the solutions and the period of heating was 1 hr. The use of O-5- and l-g portions of sulphamic acid gave results which were sli htly low. The heating time and temperature were more critical than the amount of sulphamic acl*d.