Dhond, P. V.

Khopkar, S. M.

English

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INDIAN J. CHEM., VOL. 15A, OCTOBER 1977ferred to an Erlenmeyer flask containing an excessof potassium metaperiodatc (50-100 mg) and 10ml of '"'-1M /20 borax solution. The contents of theflasks, except for arsenic(III), were boiled for 10-15min and cooled to room temperature. 2M ammo-nium molybdate (10-15 ml) followed by 10. mlof chloroacetic acid buffer (PH 2·9) and potassiumiodide (1 g) were then added and the. iodine liberatedwas titrated with O·lN sodium thiosulphate. ForAs(III) boiling was not required .. However, thereaction mixture was kept for 15 nun at room tem-perature before the addition of .all0monium molyb-date solution. A blank of distilled water wastaken through the whole process. The results arerecorded in Table 1.Estimation of bromide - A s~ita~le aliquot ofbromide was transferred to a titration flask con-taining an excess of potassium metaperiodate (?O-70 mg) and 100 ml of IN H2S04, The reactionmixture was heated on a water-bath at 80-85° for1 hr and air was constantly bubbled through thesolution to expel bromine completely. The reac-tion mixture was cooled to room temperature,neutralized with 20 ml of 5N sodium carbonatesolution and the iodate determined, as before,after masking periodate with molybdate. Theresults are recorded in Table 1.The authors express their thanks to the autho-rities of the Regional Engineering College, Kuruk-shetra, for providing research facilities.TABLE 1 - ESTIMATIONOF BROMIDE, HYPOPHOSPHITE,.PHOSPHITE,ARSENIC(III), SELENlUM(IV)ANDTELLuRIUM(I\)Taken Found Taken Found(mg) (mg) (mg) (mg)BROMIDE HYPOPHOSPHITE26·33 26·27 4·47 4·4632·92 32·93 5·47 5·4239·50 39·50 6·55 6·5846·00 46·00 7·66 7·6952·65 52·67 8·94 8·9459·25 59·20 11-17 11-16PHOSPHITE ARSENIC(III)11·32 11·33 9·37 9·3814-15 14-13 11·24 11'2516·98 17·00 13-11 13-1318·81 18·80 14·98 14·9422·64 22·67 16·86 16·8828·30 28·27 18·73 18·69SELENIUM(IV) TELLURIUM(IV)11·25 11'25 15·47 15·5214·07 13·95 23·21 23-1816·88 16·91 30·94 30·8419·69 19·54 38·68 38·6022·50 22·50 46·41 46·3628·13 28·03 54·15 54-02References1. KAUSHJK, R. L. & RAJENDRA PROSAD,J. Indian chem,Soc., 46 (1969), 923.2. WILLARD, H. H. & GREATHOUSE,L. H., J. Am. chem,Soc., 60 (1938), 2869.3. BURNEL, D., C.r. hebd. Acad. Sci. (Patis), 261 (1965), 1982.934Solvent Extraction of Galliumwith Thiothenoyltrifluoroacetone: DirectPhotometric Determination with Rhodamine B.P. V. DHOND & S. l\I. KHOPKARDepartment of ChornistrvIndian Institute of Technology, Bornbav 400076Received 29 N ouembcr 1976; accepted 10 M arch 1977Thiothenoyltriftuoroacetone has been used for thesolvent extraction of gallium. About 12·6 Ilg ofgallium is quantitatively extracted at pH 6·5-7·5 with10 ml of O'OOIM STTA in benzene. Gallium is deter-mined in the organic phase spectrophotometricallyas a colourcd complex with rhodamine B at 580 nrn,The system obeys Beer's law in the concentrationrange 0·126-1·89 JigGa(III)!ml. The complex is stablefor 24 hr. The molar absorptivity is 3·3 X104 mol-1em- and s enstttvtty is 0·002 Jig/em". Gallium has beenextracted and determined in a single extraction inthe presence of many dements associated with it.such as indium, thallium and aluminium.AMONGST ~-diketones, acetyl •.cetoml-3 wr s usedat PH 6-9 for the extraction of gallium. Notonly the extraction was incomplete (97%), theprocess was time-consuming cs it involved too manysteps. The complexes of g81lium, indium ar;d alu-minium with trifluoroacet ylacetons.s were separatedby gas chromatography. Benzoylacet one arid diben-zoylmethane- were used for the extraction of galliumat pH 4-5'5. The synergistic extraction of gallium withthenoylti ifluoi oacet one (TTA) and t etraphenylarso-nium chlorides was also reported, but this methodsuffered from several disadvantages, namely thatthe extraction was feasible at macrograrn Concen-tration, the PH of the extraction was very narrowand it was essential to use high reagent concentra-tion. The extraction occurred only in the presenceof the acetate ions.A method for the solvent extraction of galliumwith TTA was developed by us", However, thismethod is not so sensitive in comparison to thio-thenoyltrifluoroacetone (STTA) method, now beingdescribed in this paper, as the solvent systememployed, viz. xylene, is not as efficient a solventas benzene. It is observed that colour ed species,RHGaC14, is more soluble in benzene than in xylene.Further Ga(TTA)3 is not as easily dissociated asGa(STTAh for colour development with rhodamineB. The PH for complexation for TTA is 4·5 whilefor STTA it is 6·5.The method proposed in this paper is advantage-ous, as it is possible to separate gallium from indium,thallium and aluminium, with which it is usuallyassociated. The method is selective as it is possibleto separate gallium from a large number of elementsat trace concentrations.Spectromom 204 spectrophotometer, digital PHmeter (ECIL) and a wrist action fl. sk shaker wereused. Thiothenoyltrifluoroacetone (STTA) was syn-thesized by the procedure of Berg et al», A solution(O·OOlM) of STTA was prepared in benzene. A0'5% solution of rhodamine B (BDH) was preparedin 6M HC!. A stock solution of Ga(III) wasprepared by dissolving gallium nitrate octahydrate(0·36 g) in distilled water (100 ml) containing nitricacid (1'Yo). The solution was standardized gravi-metrically? and was found to contain 0·63 mg ofgallium per ml. It was diluted to get the desiredconcentration.General procedure - An' aliquot of gallium nitratesolution containing 12·6 [lg of gallium was takenand the PH adjusted to 6·5-7·5 with O'OIM nitricacid and O'OIAf ammonia solution in a total volumeof 25 m!. It was then shaken in a separatory funnelfor 5 min with 10 ml of O'OIM STTA in benzene.The two layers were allowed to settle and separate.The aqueous phase was carefully withdrawn. Theorganic layer was Once again shaken with 10 ml of6M hydrochloric acid containing 1 ml of 0·5% rhoda-mine BIO for 5 min. The two layers were allowedto settle and separate. The red-colour ed complexwas measured spectrophot ometricallytv at 580 nmagainst the reagent blank. The concentration ofgallium (III) was computed from calibration Curve.Nature of complex species - In the extractionwith ~-diketoneit is presumed that HSTTA combinedwith Ga(III) to form chelate at PH 6·5 in accordancewith Eqs. (1) and (2).HSTTA~H+ +STTA-Ga3++3(STTA-)-+Ga(STTA)3'" (1)... (2)Now On equilibration of organic phase at 6Mhydrochloric acid, the complex breaks to GaC14,which on association with RH+ (R = rhodamineB, t etraet hylrhodamin e) gets extracted as ion as-sociated complex. The mechanism of formation ofion-associated complex may be represented byEqs. (3-5).Ga(STTAh~Ga3++3STTA- (3)Ga3++4CI-~[GaC14l (4)RH++GaCI4~[RH+ : GaCI;]O (5)Thus metals forming chloroanions with singlecharge give a 1 :1 rhodamine B salt which is extract-able. The other less important species of the dyeare RH~+ and RH3;, but in 6M HCI only RH+ existsand the coloured species formed is RHGaCl4 (ref. 11).Rhodamine B chlorogallate is soluble in water andusually extracted to different extent by differentaromatic hydrocarbons like xylene and benzene.Absorption spectra - The absorption spectrum ofGa(III)-rhodamine B complex in benzene containingSTTA [Ga(III) = l'8xlO-5M] showed strong ab-sorbance at 580 nm. The absorption maxima forSTTA is around 420 nm and it showed negligibleabsorbance beyond 520 nrn. Thus the absorbancemeasured at 580 nm is exclusively dueto RHGaCJ4against the reagent blank. Hence aJl the measure-ments were, therefore, carried out at 580 nm. Thecolour of the complex is stable at least for 24 hr.Hence the absorbance was measured within 24 hr.The molar absorptivity was 3·3 X 104 mol'? cm2at 580 nm on the basis of gallium contents. Thesensitivity of the method as defined by Sandell was0·002 (J.g/cm2•NOTESEffect of pH - The extraction of gallimn(III) inSTTA-benzene was studied over the PH range 1-10.The extraction was 10,67% at PH 1 and increasedto 95% at PH 6·0. The optimum PH for quanti-tative extraction of gallium was 6'5-7·5. The ex-traction decreased beyond PH 8'0. The pH} was3·80.The period of equilibration was varied from 1 to20 min on a wrist action flask shaker. The extrac-tion was quantitative after 5 min of equilibration.Effect of salting-out agents-Ammonium, sodium,potassium, calcium and magnesium nitrates weretested as the salting-out agents in the con cer.tra-tion range I-3M. It was observed that n on e ofthe salting-out agents enhanced the ext rs ct ionof gallium.Verification oj Beer's law - Varying amounts ofgallium(III) (1'126 (J.g-l·89 [lg/ml) were extractedat PH 6·5 as per the general procedure. Theabsorbance was measured at 570, 580, 590 and 600nrn. It was observed that system obeyed Beer'slaw at PH 6·5-7·5 over the concentration range of0·126-1·89 [lg/ml of gallium at 580-590 nm.Effect of varying reagent concentration - All fact OISbeing kept constant concentration and volume ofthe reagent were varied. The extraction was in-complete at [reagent] lower than O·OOIM. Therewas no significant increase in the absorbance andhence in the extraction, when the concentrationof reagent was increased from 0·001 to 0·002M.The use of varying volumes of O'OOIM reagentshowed that the extraction was quantitative with10 ml of the reagent.Effect of diverse ions - Several ions were examinedfor their effect on the extraction of gallium. Thetolerance limit was set at the amount of foreign ionrequired to cause ± 2% error in the gallium recovery.The results recorded in Table 1 show that commoninorganic anions and common organic complexingagents are tolerated in the ratio of 1AOO. Most ofthe other ions are tolerated in the ratio of 1AO and1 :20. The ions showing strong interference areTABLE 1 - EFFECT OF DIVERSE IONS[PH = 6'5; Ga(III) = 12·6 ILg; and STTA-benzene =1·0 xlO-3.'H]Tolerance limit1 X 103 Ilg5·0Added ionsSr'+ Ba'+ R b" Cs+ 1- CN- SCN-S'-01-, soi- S'Oi-, 'pot,~cH3COO-:C.O!-, Tart3-, Malon '-, AscorbSeOi-, TeOi-Hg2+, Sb3+, Pt4+, Ir3+, Rh3+, OS3+,Ru3+,AI"+, Ni2+, Th4+, z-«, Be"+, Ge4+, ReO.,F-, Cit3+Ag+, Pb+, rt-. Cu2+, Cd2+, Au3+, PdH,Ti4+, Fe3+, Mn", Sn'+, In3+, 1"Io70~iWO~-, VO.Bi3.+, Zn2+, UH, EDTA4-2·00'50·25NoneInterference eliminated by masking Sb(III), Rh(III),R,:(III) an~ Zr(IV) with tartaric acid, Mn(II) with oxalicaCId., The Inte~erence due to Pd(lI) was eliminated by ex-traction with dimethyl glyoxime and that due to Fe(III)by extraction with acetyl acetone.935INDIAN J. CHE:.vI., VOL. 15A, OCTOBER 1977bismuth, zinc, cobalt, uranium(VI), EDTA andascorbate. Several sequestering agents were usedto eliminate the interference of some of the ions,e g. antimony(III), rhodium, ruthenium, zirconiumand cerium(IV) were masked with tartaric acidwhereas manganese was masked with oxalic acid,The interference due to palladium and iron(III)was eliminated by selective extraction-s withdimethylglyoxime and acetylacet one respectively.The method is rapid as extraction and deter-mination required only 30 min. As little as 0·126[Lgper ml of gallium can be determined. The resultsare reproducible. The average recovery of galliumis 99·8 ± 0·2%. The relative standard deviation isis ±1·12%.References1. KRISHEN, A. & FREISER, H., Analyt. cu-«, 31 (1959),923.2. STEINBACH, J. F. & FREISER, H., Analyt. cu-«, 26(1954), 375.3. JASKOLSKA, H. & :\IINCZEWSKI, J., cu»: Anal. (lVal'saw),12 (1967), 697.4. S\\TET, T. R., Anal. cu,« Acta, 37 (1965). 1552.5. STARY, J. & HLADKY, E., Anal. Chim. Acta, 28 (1963),227.6. RAHAl';fAN, M. S. & FINSTE:-i, H. L., Analyt. cu«, 40(1968), 1709.7. DHOND, P. V. & KHOPIO.R, S.M., T'alanta, 23 (1976),51.8. BERG, E. \V. & REED, K. P., Anal. Chim. Acta, 36(1966), 372.9. KOLTHOFF, 1. xr. & ELV'ING, P. J., Treatise on analyticalchemistry (Interscience, ~ew York), 196+, 252.10. CHARLOT, G., Colorimetric determination. of elements(Elsevier, Amsterdam), 196+, 252.11. SANDELL, E. B., Colorimetric determination of traces ofmetals (Iuterscience, New York), 1959, 210.12. DE, A. K, KHOPKAR, S. :vr. & CHAL~!ERS, R. A., Solventextraction of metals (Van Nostrand-Reinhold Co.,London), 1970, 98, +8.Use of Some Phenolic & pyrazoloneDerivatives as Acid-Base IndicatorsS. C. :\iISHRA, (:VIrs) SARO]BASINI DAS & A. S. MITTRA*Mayurbhanj Chemical Laboratory, Ravenshaw CollegeCutback 753003Received 23 October 1976; accepted 24 February 1977Nitro, nitroso, amino, hydroxylamino, hydroxyand carboxy derivatives of some phenols and 2-pyra-zotin-s-ones have been prepared and their use asacid-base indicators studied. The pKID values, pHrange, and colour in acidic and alkaline media arereported for the indicators. It is found that the pKlvvalue for I-phenyl-3-methyl-4-amino-2-pyrazolin-5-one tallies with that of methyl orange (3,7), and ithas also comparable stability. Hence its use as asubstitute for methyl orange is suggested.WHILE preparing various phenolic and 2-pyra-zolin-Svone derivatives in the course of ourinvestigation on fungicides against blast diseaseof rice plant, we observed that some of these=To whom all correspondence should be addressed.936compounds behave as neutralization indicators.It is known! that phenolic derivatives like p-nitro-phenol, cresol red, etc., act as indicators in acid-basetitrations. According to chromophore theory, thepresence of -N02, -NH2' -NHOH and -OR groupsenhances the sharp colour change from acidic toalkaline medium or vice versa. The presentseventeen compounds, having both chromophoreand auxochrome groups, satisfy all the requisitesof ideal indicators'',2-Nitroso-, 2-carboxy- and 2-nitro-resorcinols, 2-nitro-Lsnaphthol, 2-nitro-1-naphthol-3 -carboxylicacid, 3-nitro-1-naphthol-2-carboxylic acid, l-nitro-Z>naphthol, 1-nitro-2-naphthol-3-carboxylic acid and3-nitro-2-naphthol-1-carboxylic acid (Sr No. 1-9,Table 1) were prepared by standard methods+".1-(2,4- Din itrophenyl) -3-meth yl- 2-pyrazolin- 5-one (SlNo. 16, Table 1) was also prepared by a reportedprocedure",For the preparation of 6-nitro-o-cresol, 3-nitro-p-cresol and 6-nitro-m-cresol (Sl No. 10-12, Table 1),each of the compounds, a-cresol, p-cresol andm-cresol (2 g) was dissolved separately in pyridene(20 ml) and cone. HNOa (10 ml) added dropwiseuntil effervescence stopped. The contents werecooled for 1 hr and ice-water (20 ml) was added.The separated compounds were filtered, recrystallizedfrom ethanol; m.p. 69·5° (Sl No. 10), 77° (Sl No. 11),56° (Sl No. 12); yield 65-75%.For the preparation of I-phenyl-3-methyl-, 1-acetamido-S-methyl- and 3-methyl-4-hydroxy-amino-2-pyrazolin-S-ones (Sr No. 13-15, Table 1), the threedifierent 4-ni troso-z-pyrazohn-S-onest (1 g each)were dissolved separately in the minimum amountof absolute ethanol and zinc (1 g) and calciumchloride solution (10 ml) were added. The mixtureswere then refluxed over a water-bath for 1 hr, oruntil there was a marked colour change in thesolution. The reaction mixture was filtered hotand excess of ethanol evaporated off. It was thenallowed to cool (kept overnight) when crystalsseparated. The compounds were filtered, recry-stallized, analysed for C, Hand N. The analyticaldata are given in Table 2.For the preparation of 1-phenyl-3-methyl-4-amino-2-pyrazolin-S-one (Sl No. 17, Table 1), l-phenyl-J>methyl-Zspyrazolin-Scone" (1 g) was dissolved inthe minimum amount of sodium hydroxide solution(10%). The solution was heated over a low flamewhile stirring it continuously. Solid sodiumdithionite was added in small portions until theyellow colour of the solution changed to orange-red.The reaction mixture was kept overnight, whendark red crystals separated. The compound wasfiltered, recrystallized from ethanol, m.p, 186°, yield70%. The same compound was also obtained, bycarrying out the reduction in zinc and acetic acidmedium (Found: C, 63·39; H, 5·81; N, 22·12.ClOHnN30 requires C, 63'49; H, 5·82; N, 22·22%).Preparation of the indicator solutions - 0·05 g 0:the indicator sample was dissolved in the minimumvolume of ethanol at room temperature and volumemade up to 100 ml by the addition of distilled water.In some cases, a slight precipitate was formed atthis stage, which was filtered off.

Solvent Extraction of Gallium with Thiothenoyltrifluoroacetone: Direct Photometric Determination with Rhodamine B

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Solvent Extraction of Gallium with Thiothenoyltrifluoroacetone: Direct Photometric Determination with Rhodamine B

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