SU715477A1 - Method of amperometric determination of vanadium (iv) - Google Patents

Description

. The invention relates to analytical chemistry and can be used in non-ferrous metallurgy, chemical, electronic industry, in the analysis of special grades of glass, building materials. A colorimetric method for the determination of vanadium is known, based on the extraction of V (ly) with isoamyl pyrophosphoric ether and subsequent photometry of the extract. At the same time, the presence of any quantities of the elements Zn, Cd, Pb, Fe (nd), Mh (), AI, Cp, Cu, Or (-1), and 2-3 g of Fe (in), Ni does not affect the accuracy of the method ( error “4%). Vanadium (V), which is present in solution, previously; restore ascorinic acid tsuy or sodium sulphite 1. This method eliminates some of the drawbacks, but does not allow direct and direct determination of wANadi (ly) in the presence of vanadium (V). This also reduces the accuracy of the determination of the content (1), which is indicated by a large determination error (44%). In modern industry, for technological purposes in metallurgy of rare and non-ferrous metals, for chemical analysis in various productions, it is required to know precisely the low (up to 0.4%) content of vanadium (IV) in the presence of vanadium (mg), titanium (G) titanium ( Iv) chromium (TE) and other elements. It is known, for example, that the physicochemical properties of vanadium-based optical glasses depend on its content (IV). The closest to the technical essence and the achieved result is the method of determining vanadi5G CW), which includes amperometric titration on a rotating platinum disk electrode with a solution of hashlocyanin at appropriate pJ values, in the presence of vanadium (Y), titanium (m.) When analyzing complex objects, the determination accuracy is satisfactory, besides this method is more suitable for determining macroquantities of vanadium (IV), in this case the absolute and relative errors are reduced, the known method is also not sufficiently selective. The purpose of the invention is to increase the sensitivity, selectivity and accuracy of determination of trace amounts of vanadium (IV) (up to 0.4%) with the simultaneous and joint presence

Vanidi (y), titanium (HL), tinate (JV) and chromium (JH.).

The goal is achieved by using an organic reagent class of a triphenylmethane series R-eriochromo cyanine R (ELC) and a physico-chemical method of analysis-amperometric titration on a rotating platinum disk electrode. Titration is carried out with a 0.001-0.0.2 M solution of eriochromo cyanine R at a pH of 4.0-4.5.

The essence of the invention is cJie yJbigHM i

Vanadium (1) forms, with eriochrome cyanine R, in optimal conditions the vanadium (IV) complex compounds of the composition of the composition vanadium (IV): ECT — 2: 1, 1: 1, and 1: 2, characterized by the constants of instability and half-wave potential. Vanadium complex compounds

fIV) with eriochrome cyanine D are also formed at pH 3, their device decreases with time, therefore, in more acidic environments, vanadium (IV) compounds with the reagent are destroyed,.

for amperometric titration-. Neither is used by the known instal-. ka with a rotating platinum. disk electrode with a visual reading of the current strength (type M 91 / A galvanometer

and tension. As an electrode;: confusion. Using a saturated caltomel electrode. Rotation speed

a platinum electrode is; ; 900-1000 o6 / MkifJV - ---- V ".. J ..; The initial raw materials for analysis are industrial samples obtained in the technological conditions of production of various optical glasses and. Vanadium and metal metals. Primer p. A portion of the glass 0.2, 0.5 g is decomposed in a mixture of sulfuric and cobalt acids in a nitrogen atmosphere (the case of vanadium (g) and Chitan

(G), which are easily oxidized in air) and evaporated to wet salts.

;. To the water of the rest of the tide piece 20 ml of hot water and on: hotosd tdd workout -; Rhenium salts. The solution is poured into

50 ml volumetric flask, neutralized with caustic soda to pH 4.5, d6. 10 ml acetate buffer

The solution is brought to the mark with water (in a stream of nitrogen to avoid oxidation, vanadium (L), to vanadium (TU).

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After stirring, an adequate portion of the solution is taken into the electrolysis cell, where 2 ml of the background solution is located. (2m sodium perchlorate solution) and amperometric titration of vanadium (IV) with eriochromyanine R of exact concentration in the range of 0.001-0.02 M, for example, 0.002 M, wait every time after. addition of the working solution (ECT) until direct current (in 30 s) is established. The overlap potential is 0.5-0.6 V.

The graph is plotted in the coordinates: current strength (division of the scale of the galvanometer, in mA) - the volume of the reagent solution (in ml). From the graph on the inflection point (on the equivalence point), the volume of the reagent solution that was titrated is determined and the vanadium (IV) content is calculated using the formulas

,, 50,95.a.lOO.VK,,

H.Vn.lOOO;

. or 5.095. but. VK

f III I. I -I. f

I, Vn,

where X is the content of vanadium (IV),% V) is the volume of the volumetric flask, ml; Vj - pipette volume (aliquot

parts), ml; , H - sample weight g; a is the volume of reagent at the point of equivalence (ml), multiplied by the exact concentration of eriochrome cyanine R, M; 50.95 gram equivalents

numerically equal to its atomic mass ...., -; . The developed method was tested on industrial samples obtained under the technological conditions of the electrolytic production of pure vanadium / and titanium metals, optical and quartz glasses, which included titanium (t), titanium (IV), vanadium (S) / vanadium (IV ), as well as the following metal cations and anions; , K, Rb, Cs, AI Ca% Or jE), Ca (Gu) / Fe (L), Fe (M) Mg As / Pb Ba-: 2; n: co Ni%

310/7, CI, -NO,

With r 2 - tpl.Z it. -

so

4 / NH |, CHg, .COO and DR.

The results of determination of vanadium (IV) content in optical glasses are given in Table. one,

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.Table 1

The results of determining the content of 20 vanadium (IV) in the samples technology; Production of pure vanadium metal is given in tab. 2, T a B L I C a 2

Claims (2)

Claim 1. Method for the amperometric determination of vanadium (IV) in complex objects. Order 9610/3 max. in order to increase the selectivity and accuracy of determination. . of trace amounts of vanadium (IV), eriochrome cyanine R is used as the organic reagent irpol 5Q. <. 2. The method according to p. 1, characterized in that the titration is carried out with a 0.001-0.02 M solution of eriochrome cyanine R and a pH of 4.0-4.5.