Bakore, G. V.

Hiran, B. L.

Joshi, S. N.

English

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Procedure - In the volumetric method, excesspotassium dichromate was added to a known volumeof N2H4 (the ratio of dichromate varying from 1: 2to 1: 25 depending upc;n the concentraticn of hy-drazine) and acidity adjusted to 0·2-0·8N HCI.After 5 min, 10 ml of KI (10%) were added andsolution titrated against standard sodium thio-sulphate at room temperature under "proper condi-tions". Blank titrations have shown that thereaction between N2H4 and K2Cr207 is completedin 5 min before the addition of KI.In the potentiometric procedure, the oxidationprocess involves the direct titration of N2H4 withK2Cr207 or the reverse process at an acidity rangingbetween 3 and 5N HCl in the presence of 0'015MCUS04' where a sudden change in the potentialindicates the end point. The titration apparatuswas the same as previously described".The oxidation of N2H4 with excess K2Cr207 wasinvestigated at different acidities and time intervals.At lower acidities « 0·20N Hel), the reaction isslow and requires 15 to 30 min for completion.However, in 0·20 to 0'80N HCI, the reaction iscompleted in 5 min. Above 0·8N HCl, the volumeof K2Cr 207 consumed is less than the theoreticalvalue which may be due to the lowering of the reactionrate.Under the optimum conditions, good results areobtained when the initial amount of N2H4 variesfrom 0·08 to 24 mg. Similarly amounts of chromiumin the range 0·17-52·5 mg can be determined withgood results.The optimum ratio of K2Cr207 to N2H4 dependson the amount of the latter. With higher amountsof N2H4 (6-24 mg), the ratio should net be less than1·5 : 1, whereas with lower amounts (4 to 0·60 mg)the ratio should be increased to 3 : 1. Higher ratioswere used for determination of micro amounts.In the potentiometric titration of hydrazinesolutions with Cr20~- at different acidities, theattainment of equilibrium at the Pt electrodeseems to be very slow even on heating to 60°. Thereaction was found to be catalysed by Cu2+ ions.The role played by Cu2-f is mainly restricted toenhance the attainment of equilibrium". Cu2-f inthe concentration range O·01-0·025M is sufficientfor successful quantitative determination of N2H4by the potentiometric method. Good end pointsare obtained at acidities ranging from 3 to 5N HClin the presence of 0'015M CUS04 at room tempe-rature. At lower acidities, the equilibrium becomesmore or less smooth at temperatures between 40and 50°C and good results are obtained. The titra-tion curves obtained are characterized be sharpinflections of the order of 280 mV per 0·1 ml KzCr 207at the end points. The potentiometric titrationcan be carried out safely at temperatures up to60°, provided the optimum conditions of acidityand Cu2+ concentration are maintained. Amounts ofN2H4 varying from 0·029 to 18 mg can be determinedwith errors not exceeding ± 0·50%. The inflectionat the end point decreases with decreasing hydrazineconcentration.The reverse reaction, reduction of K2Cr207 byhydrazine, is very slow at different acidities evenon heating to 60°. However, the reaction proceedsNOTESsmoothly at room temperature in the presence of0·01-0·025M CuSO~ and 3-5N HCI. The titrationcurves ore smooth and characterized by sharpinflections of the order of 225-235 mV/0·1 ml N2H4at the end point. 0·35-49 mg of Cr can be estimatedaccurately in the presence of appropriate amount ofCuS04 and 3N HCI.The statistical analysis of the data can be con-sidered in terms of the t-value and the coefficientof variation-'', It was found that the t-value ob-tained from the t-table with 18 degrees of freedomis much larger than the t-calc. (0,004) at all levelsof significance. Furthermore, the coefficient ofvariation correspondir.g to different amounts ofN2H4 are less than 1%. These facts indicate thatthe experimental and theoretical volumes of K2Cr207consumed by N2H4 are not significantly different.This supports the suitability of our rnethcd for thedetermination of N2H4.References1. JAMIESON, G. S., Am. J. Soc., 33 (1912), 352.2. KUTENACKER, A. & WAGNER, J., Z. anorg. allg. Chem ,120 (1922), 261.3. CAY, E. J., J. Am. chem. Soc., 46 (1924), 1810.4. BENRATH, A. & RULAND, K., Z. anorg. allg. Chem;;114 (1920), 267.5. Issx, I. M. & Issx, R. M., Analyt. chim . Acta, 14 (1956),573.6. GOPALA RAo, G. & KRISHNA RAo, P. V., Analyt. chem,Acta, 65 (1973), 347.7. VOGEL, I., A text book of quantitative inorganic analysis"(Longmans, Green, London)' 1959, 331, 336, 365.8. TOURKY, A. R., Issx, I. M. & AMINE, A. M., Analyt.chem. Acta, 10 (1954), 168.9. ISSA, I. M., MISBAH. A. S. & HAMDY, M. H., Microchem ..J., 17 (1972), 604.10. LACEY, G. L., Statistical methods of experimentation(Macmillan, New York), 1962.Synergistic Effect in Solvent Extraction ofNi(lI) with Benzohydroxamic AcidB. L. HIRAN; S. N. JOSHI & G. V. BAKOREDepartment of Chemistry, School of Basic Sciences &Humanities, Udaipur 313001Received 14 January 1975; accepted 1 April 1975The extraction of Ni(II) with benzohydroxamic acid(BHA) in the presence of pyridine or quinoline in.chloroform has been Investigated. Nickel is extractedas an ion pair (NiAL+,where A=BHA and L=pyridineor quinoline).BENZOHYDROXAMIC acid (BHA) has beenwidely used in analytical chemistry-. It is agood extracting reagent and easy to obtain. Itwas, therefore, thought worthwhile to investigatethe extraction of Ni (II) with BHA.During the course of the present studies it wasobserved that the extraction of nickel with BHAis difficult, probably because the complex formedis either not soluble in organic solvent- or takeslong time to attain equilibrium. However, in thepresence of pyridine or quinoline it forms an extrac-table complex and extraction equilibrium is attainedwithin 15 min.71INDIA N J. CHEM., VOL. 14A, JANUARY 1976Polarographic Determination of Dtrnethylgly-oximates after Extraction with Naphthalene:Trace Analysis of Ni(II) & Pd(II)TABLE 1 - DEPENDENCEOF EXTRACTIONCOEFFICIENTOFNi(II) BYCHLOROFORMIN THEPRESENCEOFADDEDSALTS[[BHA]=0'005M; [L]=1'24M and pH=6'7][Salt] NaClO. NaCl(M) --.--------Extraction q Extraction q(%) (%)0 53·7 1-16 53·6 j·l11 88'4 7-66 74·9 2·922 95·9 24·5 86·7 6·573 97·9 48'0 92·6 12·254 98·1 51'0 95·7 22'55 98·1 51·06 97·9 48·0Benzchydroxamic acid was prepared by thestandard procedure" and recrystallized; m.p. 128°.Other chemicals and solvents used were of analvticalgrade. The alcohol-free chlorofcrm was "used.Nickel perchlorate was prepared and stock solutionstandardized by the literature methods.Procedure - Nickel perchlorate solution (1 ml of1 X 10-4M) was mixed with 8 ml cf BHA and 1 mlof H20. To this was added an equal volume oforganic phase (i.e. 10 ml) containing pyridine or.quinoline and shaken for 15 min at 23° ± 1°. Thetwo phases were allowed to separate and from the.aqueous phase an aliquot (2 ml) was taken eachtime and the nickel concentration estimated spectro-photometrically at 430 nm by furildioxime method,using a quartz spectrophotometer havins; silicacells of 1 cm path length. The equilibrium pHvalue of the aqueous phase was measured with pHmeter, calibrated with standard buffer solution ofpH 4.The plot of log q against log [BHA] is linearwith a slope 'of unity, suggesting a composition ofINiAL~J for the extracted adduct. Extraction ofNi(II) is enhanced in the presence of perchlorate,chloride ions (Table 1). The extraction coefficientof 94% Ni(II) in nitrobenzene, a solvent of highdielectric constant, (D = 36·1 at 20°) indicatesthat nickel is extracted probably as an ion pair.Depending upon the extraction coefficient, thesolvents can be arranged in the following decreasing-order: butanol>nitrobenzene>chloroform>benzene>cyc1ohexane>n-heptane>CCI4• This order indi-cates that the extraction order does not entirelydepend on the dielectric constant of solvent employed:Thus, in chloroform (D = 4·80) and butanol (D =17·8) extraction is 89 and 98% respectively. _The authors wish to thank Dr Rama Shanker,.Department of Chemitry, University of Udaipur;for helpful discussions. One of the authors (B.L.H.)is grateful to the CSIR, New Delhi, for the awardof a scholarship.References1. 'NISE, 'N. M. & BRANDT, W. W., Analyt. Chem., 27(1955), 1392..2. CHATTERJEE,B.,]. Indian chem . Soc., 48 (1971), 929.3. HAUSER, R., Organic synthesis, Vol. 2 (John Wiley, 'NewYork), 1944, 67.4. VOGEL,A. 1., A text book of quantitative inorganic analysis,3rd edn (ELBS Longmans Green, London), 1961, 435.72T. FUJINAGA& B. K. PURl*Department of Chemistry, Faculty of ScienceKyoto University, Kyoto, JapanReceived 23 September 1974; accepted 8 April 1975Ni(II) and Pd(II) have been extracted as their di-methylglyoxiInate into molten naphthalene, the naph-thalene allowed to solidify, separated and dissolved inDMF and the metals determined polarographicallywith sodium perchlorate for nickel and sodium per-chlorate-perchloric acid-profan extra-24 (maximumsuppressor) for palladium as the supporting electro-lytes. A large number of foreign ions which areexpected to be reduced in the voltage range studiedor to react with the reagent do not interfere in theestimations. The results show a mean deviation of0·20jtg for Ni(II) and 0·16jtg for Pd(II). The extract onof nickel is not possible in the presence of EDTA. Themethod is fairly selective, rapid, sufficiently sensitive(the determination is possible down to 0·59ppm for Niand 0·66 ppm for Pd), However, the sensitivity can befurther increased by taking larger volumes of theaqueous phase. The method can be applied for thedetermination of these metals in the complex materials .DIMETHYLGLYOXIME has been widely utilizedin the gravimetric, volumetric, amperometric,colorimetric and extractive spectrophotometric deter-mination of Ni(II) and Pd(II)1-8. In spite of itswide use in the analysis of these metals, none ofthese methods seems to be selective. Thoughselectivity has been achieved to some extent inextractive spectrophotometric method by usingmasking agents, the method is less accurate andmore time-consuming. The selectivity may alsobe achieved in extractive polarographic method,but due to the low dielectric constant of the organicsolvents and the large volume required for thecomplete extraction it is difficult to get well-definedwaves. In certain cases well-defined waves havebeen obtained using mixed solvents", but the sen-sitivity is very much decreased in such cases. Wehave developed a new extractive polarographicmethod in which metal chelate is extracted withmolten naphthalene at high temperature, dissolvedin dimethylformamide (DMF) , mixed with thesupporting electrolyte and analysed polarographi-cally. This method of extraction is quite rapid,equilibrium is achieved in a few seconds due tohigh temperature, and a very small amount of theorganic phase is required for the complete extraction.The interferences due to various ions have beenstudied in detail.Reagents - The reagents used were of-GR quality.Nickel chloride solution' in distilled water wasstandardized gravimetricallyt. Palladium chloridesolution (0'4433 gin 10 ml of cone. HCI) was diluted*To whom all correspondence should be made at: Depart-ment of Chemistry, lIT, Hauz Khas, New Delhi 110029.

Synergistic Effect in Solvent Extraction of Ni(lI) with Benzohydroxamic Acid

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Synergistic Effect in Solvent Extraction of Ni(lI) with Benzohydroxamic Acid

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