Gupta, Y. K.

Mohan, Devendra

Sharma, P. D.

English

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INDIAN J. CHEM., VOL. 14A, MARCH 1976HCI transferred to a 25 ml volumetric flask, madeup to the mark and measured spectrophotometri-cally at 705 rim against a reagent blank preparedin a likewise manner.The reagent has a negligible absorption at 705nm. In the absence of interfering ions, a IX to-3Mreagent solution is adequate for complete colc:'urdevelopment with Fe(U). In the presence of highconcentration of foreign ions, a saturated reagentsolution should be used.The green complex obeys Beer's law in the r~~ge0·2-5·6 (log/ml of Fe(U), the molar absorphv~tyand Sandell sensitivity" at Amax (705 nm) being1·8x 10' litre mole'? cm! and 0·003 (logof Fe(U)cm-2 respectively. The colour is stll:ble inde?~ite~yat PH 4·5-6 but once it is made highly aCIdIC, Itbegins to fade slowly. The absorb<l:nc~ measur~-ments should, therefore, be made within 30 mmof the acidification of the sample-NHQS system ..The ions commonly associated with Fe (II) innatural or synthetic mixtures, viz. Al (III) , Cu(II).Ni(II). Zn(II). Mn(U). Hg(II), Cd(II) , Mg(II) ,Be(II), Cr(VI). U02(U), Ca(II), Na(I), ~(I), .aretolerated in ratios 1: 100: : Fe (II) : foreign IOn.Presence of SO~, NO;, CHaCOO-, CI-, Br! 1- .hasno effect on the determination. Complexing IOnscitrate, tartarate, ascorbate and thiosulphate aretolerated in ratios 1: 1000. Gold(III), V(IV), Ce(III),Th(IV), La(IU) and Ti(IV) are tolerated if prese~ltin concentrations 25 times to that of Fe(II) whilePt(IV), Ru(III), Os (III) , Pd(II).. Ag(I) and Co(II)can be present in a concentration comparable .tothat of Fe(II). Attempts to mask C.o(~I) wit hcitrate, tartarate, thiosulphate and mtnte wereunsuccessful.Determination of F e(II) in tap water -:- .Tap water(2litres) was concentrated to 5 ml by b<?dmg. Aftercooling, it was brought to pH~4 with HCl an.d2 ml of 1% hvdroquinone solution was added to Itto reduce Fe(III) to Fe(II) .. From this solution,Fe(II) was determined as described before. Quadru-plicate measurements yielded a value 0·84 ± 0·02ppm. 18 h dComposition of the complex - Aly et. a . aproposed that in Fe-NHQS system Fe(II) IS chelatedto the oxygens of nitro~o and .hyd.roxyl groups .ofthe ligand. The unpublished kinetic and potenhc:'-metric studies of the present workers endorse thisview and confirm that in the green complex, Feand NHQS are combined in a ratio 1: 3. .The authors are thankful to the CSIR, New Delhi,for a senior research fellowship (to SAA) andto Dr K. G. Nagarkar for suggestions.References1. MARGERUM, D. W. & BANKS, C. V., Analyt. Chem., 26(1954), 200. .. lit2. CHARLOT, G., Colorimetric determination. 0 e emen s(Elsevier, New York), 1964, 272. .3. GOR~ACH. G. & POHL, F., Mikrochimie mikrochem,Acta, 38 (1951), 258-4. DAWSON, E. C., Analyst, 73 (1948), 618.. .s CHALMARS, R. A. & DICK, D. M., Analytica chim, Acta,31 (t 964), 520.,6. DE, A. K., KHOPKAR, S. M. & CHALMERS, R. A.,Solvent extraction of metals (Van Nostrand, New York).1970.2167. SKOOG. D. A. & WEST, D. M., Analytical chemistry(Holt, Rinehart & Winston, New York), 1963,. 457.8. ALY. M. M., MIKHOYAN, M. & EL-EzABY, S., J. snorg,nucl. cu«: 35 (1973).9. SANDELL, E. B., Colorimetric determination of traces ofmetals [In terscience, New York), 1959.Hexacyanoferrate(III) as a Primary Standardfor the Determination of Sb(llI) inBicarbonate MediumDEVENDRA MOHAN, P. D. SHARMA & Y. K. GUPTADepartment of Chemistry, Ur.iversity of Rajasthan, JaipurReceived 27 February 1975; accepted 25 April 1975Arsenic(III) and antimony(III) in bicarbonatemedium can be determined using hexacyanoferrate(III). The method involves liberation of iodine frompotassium iodide by ferricyanide in the presence ofzinc sulphate and titration of this iodine with As(III)or Sb(IU).SEVERAL methods, such as gravimetric', ampero-metrics, potentiometrics, spectrophotometric+ andtitrimetric, arc available for the determination ofAs(III) and Sb(III). Amongst the various titrim~-tries methods=w indirect cerirnctric method= IIIacid medium and chlorarnine-T method" in alkalinemedium, appear to be most suitable. In the iodi~ernethodw, which is simple and is applicable IIIbicarbonate medium, iodine is not a primarystandard. Other methods of determination areeither not direct or not easy to manipulate. Re-cently silver(III)l6, copper(III)16 and N-bromosuc-cinimide-? have also been reported to react withAs(III). It has been found by Deshmukh and Sant!"that hexacynoferrate(III) can be employed for thedetermination of As(III) in bicarbonate medium.In the present note an improvement over this methodhas been suggested. It is found that KI can beadded directly in the bicarbonate medium and thatthere is no necessity of adding HeI. The deter-mination of Sb(III) is also described.Potassium hexacyanoferrate(III). zinc sulphate,sodium bicarbonate and potassium iodide were ofBDH (AnalaR) quality. Sodium metaarsenite(Riedel) was employed as source of As(I1I) and potas-sium antimonyl tartrate (May & Baker) for Sb(III).Solutions were prepared by direct weighing inredistilled water (second distillation from perman-ganate). Aqueous solutions of AS203 obtained byboiling it with water and acid solutions of Sb20aobtained by boiling it with 30% perchloric acid,could also be used. Alkaline solutions of As(III)after neutralizing it with HCI could also be used.These solutions were standardized iodometricallyw.Procedure - Hexacyanoferrate(III) solution (2-10mI) of suitable concentration, saturated solution ofsodium bicarbonate (5 ml) and potassium iodide (2 g)were taken in an Erlenmeyer flask and the volumemade up to 25 mI. 0'2M ZnS04 solution (.1ml) wasadded with shaking. The liberated iodine wastitrated against the unknown As (III) or Sb(III)NOTESTABLE 1 - DETERMINATION OF Sb(III\ BY K3Fe(CN). INBICARBONATE MEDIUM[Saturated NaHC03, 5 m1; 0'2M ZnSO., 5 ml; totalvolume, 25 ml][K3Fe(CN).J Sb(III) (mg) Error (%)used -----.-~~---Mx 10" Take'! Found20 72'9 72'')16 58·5 58·3 -0'32 3·9 43'6 -0'710 36·7 36·8 +0'38 29·0 29·1 +0·354 14·6 14·55 -0,32 7·29 7·291·6 5'86 5'88 +0'31'2 4·36 4·37 +0'21'0 3·64 3-65 +(l'3os 2·925 2·92 -0·60'4 1-46 1·455 -0,3()'2* 0'729 0·729*10 ml of ZI1S0. instead of 5 ml were used.solution from the burette using starch as an indicator.The results in most cases were within± 0·5%. Theresults with Sb(III) are recorded in Table 1.. In strongly acidic solution!" reaction (1) proceedsIn the forward right direction whereas the courseis reversed in neutral solutions.2Fc(C~- +2h=2Fc(CN)~-+I2 ... (1)In bicarbonate medium, the reaction can be madeto go in the forward direction by employing zincsulphate-". The formation of the precipitate of zincfcrrocyanide shifts the equilibrium towards the right.The use of bicarbonate medium to shift the equili-brium(2) to the right is well known.As(III) or Sb(III)+I2+H20--+As(V) or Sb(V)+2I-+2H+ ... (2)combination of iodometryThe method is thus aand iodimetry.When using hcxacyanoferratcff I I] in concentra-tion range 0·000lM-0·002M, 10 ml of 0'2M ZnSO"must be added to obtain correct results. It wasfound that larger quantities of ZnS04 are requiredif more than the recommended quantity of NaHC03is used.For Sb(III) solutions the method is not applicablefor concentrations less than 0·002M. The tolerablelimit of tartarate is five times that of Sb(III) used.The titrations cannot be performed by using hexa-cynoferrate(III) in the burette, and arsenite orantimony(III) along with RI, NaHC03 and ZnS04in the flask. The reason for this is not obvious. Awhite precipitate of unknown composition is formed.A determination with perrnanganatc underidentical conditions is also possible.References1. SZEKERES, L., KARDOS, E. & SZEKERES, G. L., Microchcm,].,10 (1966), 184.2. ZHDANOV, A. I·~. & KurWCHKINA, N. i\.., Chem . Abstr., 65(1966), 11331h3. PSZONIKA, M. & MINCZEWSKI, J., Chem, Abstr., 69 (1968),8007c; CHUGTAI, HANIF MUHAMMAD, CHAUDHARI,MUHAMMAD ASLAM & ANWAR, M., Pakistan j. scient.indo tos., 15 (1972), 37; RAMCHANDRA NAIR, C. G. &RAJASEKHARAN NAill, V., Talanta, 20 (1973), 696.4. COSOVIK, CEDOMIR & KARAS-GASPAREC, VINIKA, Chem,Abstr., 71 (1969), 18494.5. BHATTARI, D. R. & OTTAWAY, J. M., Tulania, 19 (1972),793; GYORY, S., Z analyt . Chem., 32 (1893), 415.6. NOLL, A., Chem. Ztg., 48 (1924), 845; 64 (1940), 308;CHARLOT, G., Bull. Soc. chim Fr., (194i), 226.7. GOPALA RAO, G., SAROJINI, B. & GANDIKOTA. M., Talania.,19 (1972), 74; SRmAMAN, K, Tulania. 19 (1972), 1445;KNOPP, J., Z. analyt. ci-«; 63 (1923), 96.8. Issx, l. M., ~MDY, M. H. & MISBAH, A. S, Mi crochcmJ, 17 (1972),74; KOLTHOFF, l. M., LAITINEN, H. A. &LINGANE, J. J., J. Am. chem. Soc., 59 (1937),429; LANG,R., Z. analyt cu-«, 85 (1931), 176; MCNABB, W M. &WAGNER, E. c., Ind. Engng Chem., 2 (1930), 251.9. VERMA, P. S. & GROVER, K. C., j. Indian chcm. Soc., 47(1970), 871.10. CHAPIN, R. M. j. Am. chem. Soc., 41 (1919). 351.11. ANDREWS, L. W., J. Am. chcm, Soc., 25 (1903),756; MUTS-CHIN, A., Z. analyt . cs-«, 106 (1936), 1.12. "VALDEN, G. (H. Jr.), HAMMETT, L. P. & CHAPMAN, R. P.,j. Am. chcm. Soc., 55 (1933), 2649.13. BROWN, E. G., Analyt, chim. Acta, 7 (1952), 494.14. GOLDSTONE, N. I. & JACOBS, M. B., Ind. Eng1ig Chem.,16 (1944), 206; JELLINEK, K & KRESTEFF, W., Z. anorg.Chem., 137 (1924), 333.15. JAISWAL, P. K & YADAV, K L., Talanta, 17 (1970),236.16. CHANDRA, S. & YADAV, K L., Ivt icrochem: J. 17 (1972),4.17. SARWAR, M., RANA, AMANULLAH & HAMADANI, S. P.,Microchem. t.. 16 (1971), 184.18. DESHMUKH, G. S. & SANT, B. R., J. Indian chcm . Soc.,29 (1952), 543.19. KOLTHOFF, I. M., Z. analyt, Chem., 60 (1921),454; Pharm.Wcekbl. Ned., 59 (1922), 66.20. KOHN, M., Analyt. chim, Acta, 10 (1954),405; MOHER, F.,Liebig's Ann., 105 (1858), 60.Determination of Ba(II) by Precipitation asBarium Oxalate from Homogeneous Solutionby Diffusion MethodKAZA SOMASEKHARA RAO & V. G. VAIDYADepartment of Chemistry, GOVErnment College of Engineering& Technology, RaipurReceioed 31 October 1974; accepted 11 March 1975Preparation of barium oxalate from homogeneoussolution by diffusion technique using ammonia has beenadvantageously utilized for the gravimetric estimationof Ba(I1). Precipitation is slow in the presence of am-monia and is quantitative between pH 9·5 and 10·5.Good recovertes of Ba(II) are made in the presence ofmoderate concentrations of Mg(U), Zn(II), AI(III),Co(II), Ni(U) and Mn(II). Fe(III) and Cu(II) interfere.Anions such as acetate, CI- and NO; do not interfere.THE conventional method for the determinationof Ba(II) as barium oxalate is not useful for itsquantitative estimation--". However, gravimetricdetermination of barium as barium oxalate can becarried out satisfactorily by precipitating bariumoxalate from a homogeneous solution, applying thediffusion technique. The results of such a studyare repot\ed in this note.The resultS)(Table 1) show that 60·95 to 304·76mg of barium can be determined with fair accuracy.The unprecipitatyd barium, found in the filtrate bythe tracer techniq.ue, was about 50 [Lg for 152·38 mg.J 217

Hexacyanoferrate(III) as a Primary Standard for the Determination of Sb(III) in Bicarbonate Medium

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Hexacyanoferrate(III) as a Primary Standard for the Determination of Sb(III) in Bicarbonate Medium

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