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Indirect complexometric determination of nickel(II) using 1,10- phenanthroline and copper(II) using cysteamine hydrochloride as releasing agents
Abstract
Indirect complexometric methods have been described for the determination of nickel(II) and copper(II) in the presence of various cations and anions using 1,10-phenanthroline and cysteamine hydrochloride respectively as releasing agents. Metal ions in an aliquot is complexed with EDTA and the excess EDTA is back titrated with lead nitrate/zinc sulphate at pH 5.0-6.0 (hexamine) using xylenol orange as the indicator. Reproducible results are obtained with 3.5-38.7 mg of Ni(II) and 1.27-44.48 mg of Cu(II). The interference of various cations and anions have been studied. The relative errors in both cases are found to be less than ± 0.6% and standard deviations less than 0.05 mg.
Internal migration is one of the important livelihood strategies for poor community of Bangladesh. Numerous factors
i.e. social, economic, demographic and geographic factors perpetuate poor households’ decision of internal migration.
Two-step Heckman selection model is used to analyze the factors that influence households’ decision to send migrant.
In addition, the paper also tries to shed light on the factors that mediate the migrant’s destination preference.
Multinomial logit model is used in this regard. The sample size is 26,720 households. The data manifests that age,
dependency ratio, small land holding, seasonality, crop loss and house damage are preponderance factors for internal
migration. Meanwhile, in the case of destination preference the data delineates that household sends migrant more
towards Dhaka and Chittagong rather different districts or different villages of the same district. Dhaka and Chittagong
are the most preferred destination for migration as these mega cities are endowed with employment opportunities.
However, high concentration of migrant in Dhaka and Chittagong will yield unbalanced regional development in the
long run. Therefore, it is crucial to search policy options i.e. decentralization of industrialization, creating scope of job
in other parts of the country to ensure balanced economic growth of Bangladesh.
A simple, rapid and reasonable selective Complexometric technique for nickel (II) determination using some selected hydroxytriazene as a metallochromic indicator is reported in the present study. The colour change at the end point was from greenish-yellow/yellow to colourless with sharp end point. The pH ranges were 9.3-9.7, 9.0-9.5, 8.5-9.0, 8.0-8.5 while temperature ranges were 25-60, 25-60, 25-60, 25-50 and 25-50 0 C for reagent (i), (ii), (iii), (iv), and (v) respectively. Nickel(II) was determined accurately up to concentration as low as 3.0x10-3 M for reagents (ii), (iv), and (v)) while for reagents (i) and (iii) the concentration range could be even lowered to 1.0x10-3 M for the determination of nickel (II). The ions such as Cl-, Br, NH4 + , Na + , K + did not show any interference in the determination of nickel (II) even when they were present in tenfold excess. Ba 2+ , Mg 2+ , Ca 2+ , were tolerated up to five-fold excess. However Mn 2+ , Pb 2+ , Hg 2+ , Sn 2+ , Th 4+ , Cd 2+ , Co 2+ , Cu 2+ ,Zn 2+ , interfered even at equivalent amount. The method was used to determine nickel in its synthetic alloy with maximum relative error of 0.78 when using secondary masking agent.
A complexometric method for the determination of thallium(III) in the presence of other metal ions is described. This is based on the selective masking ability of sodium sulfite towards thallium(III). At pH 5.0–6.0, hexamine, thallium(III) and other diverse metal ions (e.g., common metal ions, including copper, and rare earth elements) are initially complexed with an excess of EDTA. The surplus EDTA is titrated with zinc sulfate solution, using Xylenol Orange as indicator. An excess of sodium sulfite solution (1% m/v) is then added, the mixture is shaken well and EDTA, released from the TI–EDTA complex, is titrated against standard zinc sulfate solution. The method works well in the range 4–80 mg of thallium(III), with a relative error 0.3%. The method is applied to the determination of thallium(III) in its alloy compositions and in its complexes.
An indirect complexometric method is described for the determination of zinc(II), 1,10-phenanthroline being used as masking agent. Zinc(II) in a given sample solution is initially complexed with an excess of EDTA and the surplus EDTA is titrated with lead nitrate solution at pH 5.0–6.0 (hexamine), using xylenol orange as indicator. An excess of 1,10-phenanthroline is then added, the mixture shaken well and the EDTA released from the Zn–EDTA complex is titrated with a standard lead nitrate solution. Results are obtained for 2–32 mg of Zn with relative errors 0.6% and standard deviations ±0.06 mg. The interferences of various ions are studied. The method is applied for the determination of zinc in its alloys, ores and complexes.
After formation of the PdII - EDTA complex and other metal - EDTA complexes by use of 0.01M-EDTA and titration of the unconsumed EDTA with 0.01M-Pb(NO3)2 with xylenol orange as indicator (cf. Anal. Abstr., 1980, 38, 5B217), 1% NH4SCN soln. (2 to 12 ml; 100 mg of SCN- for each 6 mg of Pd) is added to decompose the Pd - EDTA complex, the mixture is shaken and the liberated EDTA is titrated with 0.01M-Pb(NO3)2 as before. Interference is caused by HgII, IrIII or SnIV and by >5 mg of MnII (owing to the instability of the Mn - EDTA complex). Results obtained on various alloys or synthetic soln. containing Pd and Cu, Sm, Ni or Co agree well with those by gravimetric methods. The proposed method is superior to previous methods (cf. Ibid., 1975, 29, 2B223; loc. cit.) in that SCN- yield a soluble complex when larger amounts of Pd are present and release EDTA instantaneously in the cold, and that more foreign cations are tolerated.
A complexo-titrimetric method for the determination of copper(II) in the presence of other metal ions is described, based on the selective masking ability of 2-mercaptoethanol towards copper(II). Copper and other ions in a given sample solution are initially complexed with an excess of EDTA and the surplus EDTA is titrated with zinc sulfate solution at pH 5.0–6.0 (hexamine), using xylenol orange as indicator. A known excess of 2-mercaptoethanol solution (10%) is then added, the mixture is shaken well and the released EDTA from the Cu-EDTA complex is titrated against standard zinc sulfate solution. The interferences of various ions are studied and the method is applied to the determination of copper in its ores, alloys and complexes. Reproducible and accurate results are obtained for 2.5–40 mg of Cu with relative errors 0.4% and standard deviations 0.04 mg.