SPECTROPHOTOMETRIC STUDY OF ZIRCONIUM ( lV ) WITH BENZIDINE-bis-AZOPYROCATECHOL AND CETYLPYRIDINIUM

The heteroligand complex of zirconium with benzidine-bis-azopyrocatechol and cetylpyridine have been investigated by the spectrophotometric method. The condition of complexing, composition, physicochemical and analytical characteristics of the complex have been determined. The photometric determination method of zirconium has been worked out and the influence of strange ions on the determination of zirconium(II) has been studied.

Zirconium and its compounds are widely applied in atom, electro and radio technology industry.That's why to strengthen the control over zirconium containing compounds the development of the new determination methods is a topical problem.There are many photometric determination methods of zirconium in literature [1][2][3].
In this work the main aim is to study the complex formed by zirconium with benzidinebis-azopyrocatechols and surfactants, to develop new determination method of zirconium with different samples on the basis of this complex.

Experimental part
Solutions and reagents.270 mkg/ml standard solution of zirconium was prepared by dissolving it in HF+HClO 4 mixture of high pu-rity metallic zirconium.Then fluoric acid was evaporated and separated and 4 M HClO 4 was mixed with 5 M H 2 SO 4 .27 mkg/ml solution of Zr(IV) was obtained by distilling primary solution with distilled water.5•10 -3 M of benzidinebis-azopyrocatechol (BBAP) solution was prepared in 1,4-dioxane.1•10 -3 M of cetylpyridiniumchloride solution was prepared in distilled water.
To create necessary pH medium 0.1 M of CH 3 COOH and NaOH buffer solution was used.
Devices.Optical density of colored solutions was measured on SF-46 spectrophotome-ter or KFK-2 photoelectrocolorimeter, in l=0.5-1.0 cm cuvette.pH of solutions was controlled on Cond./TDS/Temp universal pH-meter.
Method.Corresponding amount of BBAP and cetylpyridinium (CP) solutions are added into Zr(IV) solution in a graduated flask.Then buffer solution is added and general amount is brought to 15 ml and mixed.The mixture is poured into 25 ml flask and is distilled with distilled water up to 25 ml.Colored solution is poured into cuvette and optical density is measured with regard to water.Analogically the experiment is performed without using zirconium and optical density of reagent is also measured with regard to water.

Results and discussion
Absorption spectra of the complex and reagents of Zr(IV) with BBAP and cetylpyridinium in different values and wide range of wavelengths were taken.It was found out that in 1-2.5 values of pH the complex is formed.Maximum yield of the complex was observed in pH 1.5 (Figure 1), but maximum light absorption was observed in 595 nm wavelength (Figure 2).
The influence of densities of BBAP and cetylpyridinium on the complexation was studied.For maximum formation of zirconium complex optimum density of BBAP was 5•10 -3 M, but for transformation of the complex to heteroligand complex the optimum density of cetylpyridinium was found to be 1•10 -3 M. The complex is formed in excess amount of chemicals.
The complex is formed directly after adding the complex of zirconium with BBAP and CP and mixing with reagents.Addition order of reagents impacts on the complexation.Thus, certain amount of a reagent is slightly distilled and added into metal solution and this prevents protonization of a reagent.
Maximum light absorption of a complex is observed in 580-595 nm wavelength, maximum light absorption of a reagent with cetylpyridinium is observed in 510 nm, maximum light absorption of a reagent without cetylpyridinium is nm.Bathochromic shift is 85 nm.
Composition of the complex.The composition of complex was determined by straight-line method of Asmus and isomolar derive method [7].It was determined that in Zr-BBAP-CP complex molar ratio of components is as ZR:BBAP:SP=1:2:4.Photometric determination of zirconium was developed.For this purpose graduated graphic of photometric determination of Zr(IV) in optimum condition was plotted.It was determined that graduated graphic obeys the Beer's law in 2.5-20 mkg/ml density range of zirconium.
The value of molar absorption coefficient was calculated using N.P.Komar method and it is ε k =4.4•10 4 .
The influence of strange ions on photometric determination of Zr(IV) was studied.Al(III), Ga(III), Ni(II), Cu(II), Ti(IV), Mo(IV), Mn(II), Fe(II) ions do not interfere to the purpose, but F -, NO - 3 ions interfere it.Hydroxides of alkali metals interact with zirconium(IV) ammonia form white ZrO 2 •xH 2 O compound and this compound is not practically dissolved in alkalies and acids.According to research works a new determination method of zirconium was developed.Developed method was applied in determination of zirconium in standard aluminium samples.