Garg, B. S.

Singh, R. P.

English

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utility of the reagent for Cu(tI) is described inthis note. However, Pd(II) and Ni(II) were alsodetermined by a similar procedure. The pka valueof the reagent was determined spectrophotometr i-cally- and was found to be 11·36±0·02 at 414 nmand 25°. The precipitated metal chelates havethe formula (C13H9N4SOhM, where M=Pd(II),Cu(II) or Ni(II). The stability constants of thechelates of Cu(II), Pd(II) and Ni(II) have also beendetermined pH-met! ically" at 25° ± 0·5° and (J.=O·lM(NaCI04) in aq. dioxane.The reagent has intramolecular hydrcgen-bondedtrans-structure as revealed by electronic and IRstudies", Other compounds having the same func-tional group ai e also assigned a similar structurebased on NMR7 and IR data after 15N labelling",The solutions of metal ions, carbonate-free sodiumhydroxide and buffer solutions were prepared bydissolving weighed amounts of AR grade salts,and standardized by conventional methods wherevernecessary. Dioxane was purified by the conventionalprocedure. pH was measured on a CambridgeBench type pH-meter.Estimation of Cu(II) - A solution of CuS04.5H20containing 20 mg of the metal was diluted to about150 ml, and 4 ml of 10% (w/v) sodium potassiumtartrate added to it to stabilize the complex fcllowedby 2'5 ml of IN HCI to bring the PH between 2·5and 3. To this solution which might also containvarying quantities of foreign ions, a 1% (w/v)ethanolic solution cf the reagent was added inexcess (25%). The copper complex separated outas a light-violet precipitate. It was digested, filter-ed, washed and dried to a constant weight at 120°to 125°.Several determinations were made using varyingamounts of the reagent under different pH condi-tions. Completion of the precipitatic n was testedboth gravimetrically and by spot tests on the filtrate.The removal of excess of reagent by complete hydro-lysis was indicated by the formation of a bluish-black colour on adding a drop of NaOH solution,whereas incomplete hydrolysis was indicated by agreenish-yellow colour.It has been found that 10-30 mg of Cu(II) canbe determined accurately using this reagent in thepresence of eight-fold excess of Cd(II), Hg(II) andAI(III) five-fold excess of Co (II), Ni(II) and Zn(II),four-fold excess of Ti(IV), Fe(II) , Fe(III), Sn(II),Bi(III) and Sb(III), and three-fold excess of Ce(IV),Mn(II) and Zr(II).Pd(II) forms a chocolate co loured complex be-tween pH 2·5 and 3·0 whereas Ni(II) forms a deepTABLE 1 - STABILITY CONSTANTS (AT [.I.= O·IM) ANDCONVERSION FACTOR OF METAL COMPLEXESMetalConversion log K1K. Conversion log ](lK.factor factorPd(II)Cu(II)Ni(lI)0'20090·13030·121522'6622·3117·500·16510·10550·098422·9222·6317·88NOTESyellow granular complex between pH 4·5 and 5'5.Alkali and alkaline earth metals, Pb(II), Rh(II),Ir(III), Pt(IV), Tl(IV) and La (III) did not yielda more deeply coloured precipitate with the reagent.The metal chelates formed by the reagent aremore intensely colour ed, thermally stable, havemore favourable conversion factors and greaterstability constants (Table 1) than those of N-phenyl-N-(phenylazo)hydroxylamine. The presenceof a heterccyc1ic benzothiazole ring may be attri-buted to the intensification of colours of the chelatesand to a better ccordinating tendency. In repro-ducibility of the results and specificity this reagentis superior to all other reagents used for determiningCu(II) and Pd(II).The authors are grateful to Prof. J. N. Gaur forproviding necessary facilities.References1. MUKERJI, S. K., Studies of metal chelates of hydroxylamineanalogues, Ph.D. thesis, University of Rajasthan,J aipur, 1970.2. SOGANI, N. C. & BHATTACHARYA, S. C., J. Indian chem .Soc., 36 (1959), 563.3. PUROHIT, D. N. & SOGANI, N. c., Bull. chem, Soc. Japan,37 (1964), 476.4. ROBINSON, R. A., Abstract of symposium on structure ofelectrolytic solutions, Washington, 1957, 90.5. CALVIN, M. & MELCHIOR, N. C., J. Am. chem. Soc., 70(1948), 3270.6. MUKER]I, S. K. & SOGANI, N. c., Bull. Acad. Polon. su.,Ser. Sci. Chim., 23 (1975), 463.7. CHAKRAVORTY, A., BEHERA, B. & ZACHARIAS, P. S.,Inorg. chim. Acta, 85 (1968), 2.8. MITSUSHASHI, T., OSAMURA, Y. & SIMAMURA, D., Tetra-hedron Lett., (1965), 2593.Solvent Extraction & SpectrophotometricDetermination of Ru(III), Rh(III) & Pd(lI)using 1-(2' -Pyridylazo)-2-phenanthrolB. S. GARG & R. P. SINGHDepartment of Chemistry, University of DelhiDelhi 110007andA. K. RrsHIDepartment of Chemistry, A.R.S.D. CollegeNew Delhi 110021Received 14 November 1975; accepted 23 September 19761-(2'-Pyridylazo)-2-phenanthrol (PAP) forms chloro-form soluble coloured complexes with Ru(III), Rh(III)and Pd(II) with J.,max 615; 580, 625; and 610, 665 nmrespectively. The extinctions of the complexes remainmaximum and constant in the pH range 4·7-6·1;4·0-8·0; 3·0-7·0 for Ru(III)-PAP; Rh(III)-PAP andPd(II)-PAP complexes respectively. The sensitivitiesof the colour reactions are 0·0049 at 615 nm; 0·0044at 580 nm, 0·0048 at 625 nm; 0·016 at 610 nm, 0·013 at665 nm respectively. A modification of the methodenhances the selectivity for the determination ofRu(III).THE use of l-(Z'-pyridylazo)-Z:phenanthrol (PAP)as a good chromogenic reagent for transitionmetal ionsv? has been earlier determined by us.367'INDIAN J- CHEM_, VOL. 15A, APRIL 1977CharacteristicsTABLE 1 - PHYSICO-CHEMICAL CHARACTERISTICS OF THE COMPLEXESRh-PAPpH rangeColourAmax (nm)Range for Beer's law (ppm)Sensitivity of metal, {J.g/cm2 (Sandell's definition)E'maxOptimum range for accurate determination (ppm)Quantity of PAP required for complete complexationComposition (M: L)Effect of time and temperature for full complexationAmount of acetate buffer of appropriate pH added for10 ml of the solutionMean absorbance valueStandard deviationRu-PAP Pd-PAP3-0-7-0Green610, 6650-IHO0-016 at 610 nm0-013 at 665 nm6500 at 610 nm8150 at 665 nm2-0-11-754 times1:2Formed in cold,dissociates after15 min butchloroform ex-tract is quitestable2-0 ml4-7-6-1Reddish6150-3-030-0049 at 615 nm4-0-8-0Green580, 6250-4-120-0044 at 580 nm0-0048 at 625 nm23000 at 580 nm21500 at 625 nm0-5-4-010 times1:2Formed in cold,stable even onheating20500 at 615 nm0-8-3-015 times1: 240 min on boilingwater-bath andquite stable3-0 ml0-4120-0012-0 ml0-2150-0020-8150-004PAP reacts with Ru(III), Rh(III) and Pd(II) incold to give coloured complexes. This fact hasbeen made the basis for the spectrophotometricdetermination of Ru(III). Rh(III) and Pd(H) inpresence of large number of metal ions.The absorption characteristics together withvarious other physico-chemical constants for thethree complexes are summarized in Table 1_A stock solution (1X 10-3M) of PAP was preparedin 95% (v/v) methanol and subsequent dilutionswere done with methanol.The stock solution of Ru(III), Rh(HI) and Pd(H)(1X 10-2M) were prepared by dissolving AR gradesamples (Johnson Matthey, London) in concentratedhydrochloric acid and were standardized gravi-metrically using appropriate methods. The sub-sequent dilutions were done with double distilledwater maintaining requisite acidity of the solutions.All other reagents used were of AR quality.Determination of Ru(III) - To an aliquot contain-ing 8 to 30 [Jogof Ru(HI) were added 1 ml of 0·03%PAP in methanol and 3 ml of acetate buffer of pH5,5. The contents were heated for 50 min onboiling water-bath. On cooling the red colouredcomplex was extracted with 10 ml of freshly distilledchloroform. The extinction of the complex wasmeasured at 615 nm versus chloroform blanks.Determination of Pd(II) or Rh(III) - To analiquot containing 5 to 40 [Jogof Rh(III) or 20 to 115(J-gof Pd(H) were added 1 ml of 0'03% and 1 mlof 0'015% PAP in methanol for Rh(IH) and Pd(lI)respectively. pH were adjusted between 4·0-8·0for Rh(III) and between 3·0 and 7·0 for Pd(II)using acetate buffers. The greenish complexeswere extracted with 10 ml portions in chlorofcrm.The extinctions were measured versus blanks at 625and 665 nm respectively,To study the effect of foreign ic ns, a series cfsolutions containing fixed amount of Ru(llI) (2'02ppm) or Rh(III) (1'03 ppm) or Pd(H) (10·64 ppm)were prepared in presence of number of foreign ionsand the amount of metal icn detei mined by follcw-368ing the recommended procedures. The limits oftolerance for various diverse ions in ppm, in theestimation of Ru(lIl). Rh(IH) and Pd(II) are givenbelow:In the estimation of Ru(III), sulphate and chloride(1000 each); bromide, iodide, fluoride, nitrate,sulphite, iodate, nitrite, calcium, barium, strontium(500 each); lead, bismuth, silver and aluminium(4 each); lanthanum (100), arsenic, auric and zirco-nium (5 each); thorium, chromium (50 each);platinum, mercury (10 each) do not interfere.EDTA, citrate, tartrate, and oxalate prevent theformation of complex, while thiosulphate, thiourea,thiocyanate, phosphate and borate interfere seri-ously. Cu(H), U (VI), Fe(II), Fe(III), Co(II), Os-(VIII), Ni(II). Cd(II), Zn(lI) , Pd (II). Rh(III). Ir(lIl).V(V) and Mn(II) interfere as they also form colour-ed complexes at rcom temperature.Bromide, fluoride, sulphate, nitrate, iodate, cal-cium, strontium (500 each), mercury, iridium, ruthe-nium, gold, aluminium, tin, silver, titanium (6 each);chromium, thorium (50 each); lanthanum (100),manganese, gallium, bismuth, arsenic (3 each) donot interfere in the estimation of Rh(III). Seriousinterferences are caused by thiocyanate, iodide,thiourea, thiosulphate, phosphate, citrate, tartrate.Fe(lI, III), Pd(II), CU(Il), Co(II), Cd(II), Zn(II),Ni(II), Mn(II), V(V) and U(VI) interfere due to theformation of coloured complexes. The interferencesdue to iron (100), aluminium (15) have been avoidedusing fluoride as masking agent. The interferencedue to mercury and lead were avoided by keepingchlorofoi m extract for about an hour, during whichmercury and lead complexes dissociate completely.Bromide, nitrate, phosphate, calcium, bariumstrontium (500 each); fluoride, lanthanum (200each); sulphate, chloride (1000 each); tartrate (40)oxalate (10), mercury (20), aluminium (10), lead, bis-muth (50), tin, magnesium, platinum(IV), gold (10each); silver, ruthenium, csmium, iridium (5 each);uranium (1-5), zinc (1-5), nickel (1'0). cadmium (1'5),manganese (1'5) do not interfere. Interferences dueto 2 ppm each of Rh(III), V(V), and Fe(III) wereavoided by using tartrate (20 ppm) as maskingagent. Still large amounts of iron and aluminiumcould be tolerated in presence of fluoride ions. Forremoving interferences due to zinc, cadmium andnickel, the initial pH 5·5 was raised to 8·0 and afterextraction with chloroform the pH of the aqueousphase brought again to 5·5 by adding acetic acidfollowed by acetate buffer of pH 5·5. Added 1 mlof 0·03% PAP again. The solution was heatedon a water-bath for 50 min, ceoled and extractedwith 10 ml portions of freshly distilled Chloroformand the extinction measured at 615 nm againstchloroform blanks.The authors are thankful to CSIR, Yew Delhi,for the award of fellowship to one of them (A.K.R.).References1. CHISWELL, B.. LIOKS, F. & TOMlLNSO:-l, 1\1., l norg, Chem.3 (1964), 4922. K-\WASE, A., Japan Analyst, 18 (1969), 463.3. RISH[, A. K. Metal chelates of 1-(2'-pyridylazo)-2-phenan-throl , Ph. D. thesis, Univcrsitv of Delhi, Delhi, 1972.4. RISHT, A. K., GARG, B. s. & SI:-IGH, H. P., Curro Sci.,41 (1972), 1555. RISHI, A. K, GARG. B. S. & SI:-,'GH, R. P., Indian J.cue«: 10 (1972). 1037.6. RISHI, A. K., G.~RG, B. S. & SI:-lGH, H. P., Curl' sa.41 (1972), 117.7 RISH[, A. K., CARG, B. S. & SI:-IGH, R. P .. Z. analyt,cso«, 259 (1972), 288.Potentiometric Estimation of PotassiumOctacyanomolybdate(IV)P. K JAIN & K N. SHARMADepartment of Chemistry, D.A.V. College, MuzaffarnagarReceived 29 June 1976; accepted 28 October 1976Potentiornetrfc estimation of potassium octacyano-molybdate(IV) in hydrochloric acid medium in the pre-sence of iodine monochloride ustng potassium iodateas titrant is described. The method affords satisfactoryand reproducible results in 6 to 7M HCl.VERY few methods are available in literature onthe estimation of octacyanornclybdates. Theutility of Mn(VII) , Ce(IV), Cr(VI) and Mn(III)compounds in potentiometric determinatien ofpotassium octacyanomolybdate(IV) in sulphuric acidmedium have been investigated". Applicability ofhalogen containing oxidants in the estimation ofpotassium octacyanomolybdate(IV) has not beenexplored as yet. Moreover at present no method isavailable for estimation of potassium octacyano-molybdate(IV) in hydrochloric acid medium. Thiscommunication deals with the potentiometric estima-tion of potassium octacyanomolybdate(IV) withpotassium iodate in hydrcchloric acid medium usingiodine monochloride methc d.Potassium octacyanomolybdate(IV) was synthe-sized by the recommended method" and its solutionwas prepared and standardized as reported earlier".Iodine monochloride was prepared by the usualmethods. The standard solution of potassium icdateNOTESTABLE 1 - POTEI>TIOMETRIC ESTIMATION OF POTASSIUMOCTACYANOMOLYBDATE(IV) II> 6M Hel WITH POTASSIUMIODATE AFTER PRETREATMENT WITH IODINE MONOCHLORIDEPctassium oct acyano- Errormolybdate(IV) (mmole) %Taken Found0·0951 0·0950 -0,100·1237 0·1230 -0·570·1521 0·1510 -0·720·1807 0·1790 -0·940·2610 0·2580 -1-160·3420 0·3380 -1-160·5140 0'5180 +0·790·4285 0·4340 +1·30was prepared by the recommended rnethod-. Thee.m.I. measurments were carried out on a OSA\VAvernier potentiometer in conjunction with a spotgalvanometer. A bright platinum foil was used asindicator electrode. A saturated calomel electrodeserved as reference electrode.An aliquot of potassium octacyanomolybdatefl V)solution was placed in a titration cell and 6 ml ofiodine monochloride solution was added. Therequisite amount of cone. hydrochloric acid wasadded to the mixture so as to make the overallacidity 6M in a final volume of 50 m!. Thereaction mixture was cooled and titrated potentio-metrically with potassium icdate solution. Theend point was located using analytical (derivative)method. The results are given in Table 1. Ithas been observed that an overall acidity of 6-7Mwith respect to HCI gives satisfactory and repro-ducible results. Erratic results are obtained if theacidity is less or more than 6-7M. In 2M HCI noinflection is observed.In the present case, iodine monochloride is thereal oxidant. Iodine monochloride oxidizes potas-sium octacyanomolybdate(IV) to octacyanomolyb-date(V) according to Eq. (1).2K4[Mo(CN)sJ+2ICl=2K3lMo (CN)sJ+Iz+2KCl ... (1)The iodine liberated frem iodine moncchloridein amounts equivalent to that of octacyanomolyb-date(IV) is oxidized by potass ium icdate to iodinemonochloi ide in concentrated hydrochloric acidmedium.'The results are low below 5'5M HCI prcbablybecause of incc mplete reaction (1) and air oxidationof octacyanomolybdate(IV). The over consump-tion of iodate abcve 7·5M HCI is perhaps due topartial decompositicn of cctacyanc molybdate(V)to an oxidizable Mo(V) species.References1. MALIK, W. C. & ALl, S. I., Indian J. Cheni., 1 (1963),374.2. FIESER, L. F.,.J. Am. C11t111. Soc., 52 (1930)' 5226.3. JOSHI, D. P. & SHARMA, K. ::\., Z. phys . Chemic, Leipzig,246 (1971). 28t.4. \'OGEL, A. 1., A text book of quantitative inorganic analysis(Longmans, Green, London), 1962, 381.5. KOLTHOFF, 1. M. & BELCHER, R.. Volumetric analysis,\'01. 3 (Interscience, New York), 1957, 234.369

Solvent Extraction & Spectrophotometric Determination of Ru(III), Rh(III) & Pd(II) using 1-(2' -Pyridylazo)-2-phenanthrol

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Solvent Extraction & Spectrophotometric Determination of Ru(III), Rh(III) & Pd(II) using 1-(2' -Pyridylazo)-2-phenanthrol

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