TABLE 1 - PROPERTIES OF HYDROXAMICACIDS

*Amax refers to the vanadium(V) complexes. Values inparentheses are molar extinction coefficients (litre mole-!em-I).

ions by different physico-chemical methods1-S. Tennew hydroxamic acids derived from N-m-chloro­phenylhydroxylamine have now been synthesizedand their use in the estimation of vanadium(V)explored.

The acid chlorides were prepared by refluxingcarboxylic acids with thionyl chloride and distillingat low pressure6•

All attempts to obtain N-m-chlorophenylhydro­xylamine in solid state failed. Hence this wasprepared in situ and the acylation carried out by theearlier reported method7• The compounds preparedwere crystallized from benzene-pet. ether mixture.The characterization data are reported in Table 1.

For the extraction of vanadium(V), taken asammonium metavanadate, solutions (0,1% wjv)of N-arylhydroxamic acids were prepared in ethanol­free chloroform.

A Carl-Zeiss UV VIS Specord and CZ Speckol(spectrocolorimeter) with 10 mm matched silicacells were employed for spectrophotometric measure­ments.

The vanadium(V) was extracted from 4 to 7Mhydrochloric acid by 0·1% (wjv) chloroform solu­tions of N-arylhydroxamic acids following thereported methods. The spectral data of vanadium(V)-hydroxamic acid complexes are given in Table 1.Out of ten compounds studied N-m-chlorophenyl­cinnamohydroxamic acid has the highest molarabsorptivity for vanadium(V) complex (Ama", = 540nm, E = 5750 ± 50).

The colour systems are found stable for 24 hr.The order of mixing of reagent is not critical. Theintensity of violet colour is measured at the wave­length of maximum absorption. The Beer's lawis obeyed in the concentration range of 0·886 to

Amax.*nm

N (%)

Calc. Found

5,65

5,79530(4700)5,35

5,34520(4500)5·04

4·96535(5250)

5,35

5,64530(3450)4,96

5·51530(4150)

9,92

9-30540(2200)5·04

4,80540(4350)

4·61

4,44530(5200)

5,89

6·12530(3450)5·11

5·00540(5750)

98

156

165

159

122

122

119

m.p.°C

Hydroxamic acid(mol. formula)

N-m-Chlorophen ylbellzo­(C!3H!.N02Cl)

N-m-Chlorophell yl-p­toluic- (C"H12N02CI)

N-m-Chlorophen yl-p­methoxvbenzo­(C"H12K03Cl)

N -m-Chlorophenyl-phenyl- 91aceto- (C"H12N02Cl)

N -m-Chlorophell yl-p­chlorobenzo­(C13H.N02CI2)

N-m-Chlorophenyl-p- 170llitrobenzo- (C!3H9N20.Cl)

N-m-Chlorophenyl-o- 116methoxybenzo­(C,.H!2KO,CI)

N -m-Chlorophenyl-p­terbutvlbenzo­(C!7H!;N02CI)

N -m-Chlorophenylfuro­(CnHsN03Cl)

N -m-Chlorophen ylcinna­mo- (C!5H12N02CI)

INDIAN J. CHEM., VOL. 16A, JANUARY 1978

Pr~paration of N-Arylhydroxamic AcidsDer~ved from N-m-Chlorophenylhydroxylamine& 'xtractive Spectrophotometric Estimation

of Vanadium(V)

i(Miss) SHREE KUMARI AGRAWAL& V. K. GUPTA

~epartment of Chemistry, Ravishankar University; Raipur

~eceived 8 February 1977; accepted 19 Augu;t 1977i

A i rapid extractive spectrophotometric method isdesctibed for the determination of vanadium(V) withN-m~chlorophenYlcinnamOhYdrOxamicacid, which isfouncllto be the most sensitive reagent, out of the tennewl}'synthesized N-arylhydroxamic acids derived fromN-mrchlorophenylhydroxylamine. Many common ionsinc1~ing Ti(IV) do not interfere in the estimation.

!

THiE survey of recent literature shows that

~-phenylbenzohydroxamic acid (PBHA) andits apalogues are widely used in analysis of metal

92

IiI

i

St~k solution of mercury(II) perchlorate (AR)

was repared by dissolving mercury metal (AR)in h perchloric acid. Potassium iodide (E. Merck)solut on was prepared in doubly distilled water.

SOdl~m acetatejacetic acid buffers were prepared

by ixing 0·2M sodium acetate and 0·2N aceticacid n different proportions. KH2P04jNaOH bufferswere prepared by mixing 0·2N KH2P04 and 0·2NNaO in different ratios. 0·25% (wjv) solutionsof t e dyes, viz. AHP-4S, DHP-4S and CPD-4S,were prepared as reported earlier3• All other re­agen s used were of AR quality.

Re ommended procedure - To a suitable aliquotcont ining 0,25-20,3 mg of iodide was added 2-3drop of dye solution,S ml of KH2P04jNaOH oraceta e buffer of suitable pH and 5 ml of 2-propanol(to i crease effective stability constant of HgI2

form]'d). The volume was made up to 20 ml by

addi g doubly distilled water and the solution titratedagai st standard O·01M mercury(II) solution untilcolo change at the end point was orange to magentaor v olet. The tit rations could be performed inreve4e manner also.

Op~imum conditions for the above titration have

been '~vorkedout and the results are given in Table 1-Tolexplore the possibility of performing titrationsin thf presence of foreign anions and cations, titra­

tionsJ were performed by taking 10·15 mg of iodide(4 m~ of 2 X 10-2M) in 20 ml, adding diverse ions in

varY~'g proportions and following the recommended

proc ure as given above. The results of the studiesare s mmarized in Table 2.

On of the authors (J.P.G.) is thankful to the

UGcj New Delhi, for financial assistance.Refer~nces1. LO~G, G. G. & HENTZ (Jr), F. C., J. chem. Educ .• 52

/1975), 714.2. GA~G, B. 5., MEHTA, Y. L. & KATYAL.MOHAN,Talanta,

~3 (1976), 71.3. GA~G, B. 5., MEHTA, Y. L. & KATYAL,MOHAN,Analytica

fhim. Acta, 86 (1976), 323.4. GurTA, J. P., MEHTA,Y. L., GARG, B. S. & SINGH, R. P.,Jndiall J. Chem., 14A (1977), 256.

'I , 'Id ;tl

7·08 [Lg/ml. The maximum colour intensity wasobtained in the range of 4 to 7M hydrochloric acid.The absorbance increased rapidly as the mole ratioof reagent to vanadium(V) increased from 1:1 to6: 1. Above this ratio up to 100: 1 the absorbancewas practically the same. The composition of thecomplex species, as revealed by Job's method ofcontinuous variation as applicable to two-phasesystems9-11, is found to be 1:2 (metal-ligand) forall the N-arylhydroxamic acids prepared freshly.

For studying the effect of diverse ions, solutionof diverse ions were prepared from reagent gradesalts using the procedure of West12. The followingions do not interfere even if present in large excess{200 folds): Cu2+, Ag+, Be2+, Mg2+, Ca2+, Sr2+, Ba2+,B40~-, AP+, CeH, TiH, Cr3+, Mn2+, Fe3+, C02+, Ni2+,UO~+, Pb2+, Cd2+, F-, AS3+, Cl04, Hg2+, oxalate,citrate and tartrate.

ZrH, WO~-, M06+ interfere. Titanium(IV) whichinterferes if PBHA is used, does not interfere withN-m-chlorophenylcinnamohydroxamic acid. It isfound that up to 10 mg of Ti(IV) does not interferein a total volume of 25 ml containing 0·11 mg ofvanadium(V). The presence of 10 mg of Zr4+ re-duces the optical density of a solution containing0·11 mg/25 ml of vanadium(V) by 10%.

One of the authors (S.K.A.) is thankful to theCSIR, New Delhi, for the award of a junior researchfellowship.

References

1. G.UKWAD, M. D., Ph.D. thesis, Ravishankar University,Raipur, 1974.

2. PILIPENKO, A. T., SHPAK, E. A. & SHEVCHENKO, L. L.,Russ. J. inorg. Chem., 12 (1967), 237.

3. AGRAWAL, Y. K. & SHUKLA, J. P., J. Indian chem. Soc.,48 (1971), 571.

4. MEYER, R. A., HAZEL, J. F. & MCNABB, W. lVI., Analyt.ch im. Acta, 31 (1964), 419.

5. LAPATNICK, L. N., HAZEL, J. F. & MCNABB, W. M.,Analyt. chim. Acta, 36 (1966), 366.

6. 'WAGNER, R. B. & ZOOK, H. D., Synthetic organic chemis-try (Wiley, New York), 1953, 546.

7. MAJUMDAR, A. K. & G.'>.YATRI DAs, Analyt. chim. Acta,31 (1964), 147.

8. GUPTA, V. K. & TA:-mON, S. G., Analyt. chim. Acta, 66(1973), 437.

9. JOB, P., Ann. Chim. (Paris), 9 (1928), 113.10. VOSBURGH, W. C. & COOPER, G. R., J. Am. chem. Soc.,

73 (1941), 437.11. IRWING, H. & PIERCE, T. B., J. chem. Soc., (1959), 2565.12. WEST, P. W., J. chem. Educ., 18 (1941), 528.

Spectrophotometric Determination ofCa(II), Sr(lI) & Ba(II) with 5,6-DihrOffiQ-

2,3,4- trihydroxyacetophenone

R. T. SANE & J. P. N. TRAKRU

Department of Chemistry, Ramnarain Ruia CollegeBombay 400019

Received 5 May 1977; accepted 28 August 1977

5,6-Dibromo-2,3,4-trihydroxyacetophenone as a re-agent in the spectrophotometric determination of Ca,Sr and Ba has been proposed. The calcium complexhas A.max at 570nm while those of Sr and Ba have A.maxat 590 nm, The method is very simple, sensitive anddirect.

NOTES

THE colorimetric methods described in literaturefor the determination of the alkaline earths

are indirect and many of them suffer from theinstability of the colour of the complexes. Gallicacid--" as a spot reagent for these metals is notsuitable since the colour of metal-gallic acid complexis not stable. Galacetophenone has been reportedas a colorimetric reagent for calcium'',

The present paper reports the application. of 5,6-di bromo-2, 3,4-trih ydroxyacetophenone (D BTHAP)in the spectrophotometric estimation of Ca, Sr andBa. The spectrophotometric data of the complexesare given in Table 1.

TABLE 1 - SPECTROPHOTOMETRIC DATA OF THECO!\-IPLEXES OF Ca. Sr AND Ba WITH

5,6-DIBROMO-2,3,4-TRIHYDROXYACETOPHENONE

Metal Amax Ex 10' Sandell's Standardnm sensitivity deviation

ILg/cm2

Ca 570 5·75 0·0069 0·01917Sr 590 5·12 0·017 0·0472Ba 590 5·25 0·026 0·0617

The proposed indicator is more sensitive thangalacetophenone and the metal complexes are morestable in solution.

The detailed investigation revealed that the opera-tive pH range for Ca is 10·5 and 11·5 while that forSr and Ba is 12 and 13. The stoichiometry of thecomplexes was 1:1 (Job's method) and Beer's lawwas found to be valid between 1 and 10 ppm of themetals. The optimum concentration range for theeffective determination evaluated by Ringbom'smethod was found to be 3 to 8 ppm in all thecases.

The effect of diverse ions was also studied. Itwas observed that ions like Zr4+, Th4+, UO~+, Cr3+,Mn2+, Ni2+, MoOi-, Ti4+, Hg2+, Cl'', Be, 1-, NO:i,CH3COO-, CIO~, N02, CN- do not interfere. How-ever, ions like Fe3+, V5+, BrOs Cr20~- interfereseriously and should be absent. Cations like Mg2+,AI3+, C02+, Cu2+, Cd2+, Bi3+ precipitate under theexperimental conditions.

Procedure - To an aliquot containing up to 8ppm of the metal was added 4 ml of 8 X lO-3M al-coholic solution of the reagent and the PH of thesolution adjusted between 10·5 and 11·0 for Ca andbetween 12 and 13 for Ba and Sr. The solutionwas diluted to 25 ml with distilled water and theabsorbance recorded at the Amax of the complexes.The amount of metal was then computed from thecalibration curves drawn under identical conditions.

Our sincere thanks are due to Dr A. J. Mukhedkarand Dr (Mrs) V. A. Mukhedkar of the Universityof Poona for help in the preparation of thereagent.References1. O. K'AC, A. & PECH, ]., Coil. Czech. chem. Commtln., 13

(1948), 400.2. TSAO, M. U., J. bioi. Chem., 199 (1952), 251.3. DESHPANDE, N. V. & MUKHEDKAR, A. ]., Microchem: I-.

20 (1975), 165.

93