SU836587A1 - Method of chelatometric determining of ferrum(111) - Google Patents

Description

(54) METHOD OF COMPLEX-MONOMETRIC IDENTIFICATION OF IRON (HI)

I

The invention relates to the field of analytical chemistry, in particular, to methods for the determination of iron in the analysis of the basic substance in vanadium containing objects.

Titrimetric methods for the determination of iron in vanadium-containing objects based on redox reactions are known and widely used.

Their common disadvantage is the unhealthiness of a preliminary separation of iron from vanadium.

The disadvantages of these methods also include the need to remove the excess of the reducing agent used to pre-reduce Fe (G) by boiling, filtering and other operations or by adding mercuric chloride (if used as a reducing agent). do dued).

The closest in technical essence and the achieved result is the method of complexometric titration (pH of determination 1-2, indicator-sulfosalicylic acid). The determination of iron in the presence of V (IV) is difficult, since the ions

. V (IV), like Fe (III) ions, is partially bound by ethylenediaminetetraacetic acid (EDTA) at pH 1-2 2.

In this connection, a preliminary separation of V (IV) is necessary for the determination of iron. The latter is carried out by precipitation of the iron in the form of hydroxide. To be precipitated

0 100 ml of sulphate solution, sodium hydroxide is added almost to neutrality, heated to boiling and the solution is poured slowly and with constant stirring into 100 ml of hot freshly prepared 10% 5% sodium hydroxide solution. Boil the mixture for 2-3 minutes, stirring slightly, allow the precipitate to settle and filter through a medium density filter paper.

0 (the filter is pre-rinsed with a hot 5% sodium hydroxide solution containing a little sodium sulphate until 50 ml of completely colorless filtrate is obtained). The precipitate is washed with the same washing solution, dissolved in sulfuric acid, the pH of the solution is adjusted to a value of 1-2, the solution is heated to 45-50, a few drops of sulfosalicylic acid are added and iron is titrated with a solution

0 EDTA before the transition of color from wine-red to pure green. A significant disadvantage of this method is the impossibility of titrating Fe (III) with EDTA solution in the presence of V (IV) and the need for preliminary separation of Fe (HI) from V (IVJ. The disadvantages of this method include the duration of the analysis and the difficulty of determining (precipitation, filtration, washing, dilution). The aim of the invention is to simplify and improve the accuracy of determination of Fe (III) in vanadium-containing materials by eliminating the interfering vanadium {IV). The goal is achieved by the method of determining Fe {111) by titration with a solution of EDTA at pH 1-2 in the presence of an indicator after binding V (W) into an inert complex by introducing into the G-5 solution an excess of V (v) no to V (IV) at pH 10-14 and 0.53, 7 M solution of ammonium salt. A solution with a pH of “10–14 is maintained at 80 UOC for a min. Distinctive features of the invention are; adjusting the pH of the analyzed solution to 10–14, adding 1–5-fold excess V (V) to V (V) to the solution, adding ammonium salts, for example ammonium chloride, to the solution at pH 10–14. within a concentration of 0.5-3.7 M, boiling the solution for 5–15 min. When V (V) undergo changes from the cationic form (VOj)) to anionic polyforms (and others that do not react with ammonium and vanadium (IV) ions. Results of determining Fe (I) in model solutions under these conditions overestimated due to titration with an EDT solution together with Fe (11) and V (W). When V (V) is in the form of a thinner, it decomposes to a metavanadate ion in the pH range 10-14 in the range 10-14 and the metavanadation forms with ions and vanadium (IV) stable inert comp, leke, thus eliminating the effect of V (IV) on Fe (III) titration with EDTA solution at pH 1-2. Raising the pH of the solution to a value in excess of 14. It was impractical because of the irrational consumption of reagents. When determining Fe (III) in the presence of a less than one-time excess of V (v) relative to V (IV), the results of titration of Fe (III) were elevated V (W) under these conditions with titration with Fe (1H). The introduction of more than five times the excess amount of V (V) resulted in an overstated, poorly reproducible results. This is caused by equilibrium of the reaction of interaction of V (V) with EDTA in the direction of complex formation. When added to the solution (pH 1014) ammonium salts at a concentration of less than 0.5 M, overestimated results were found for the determination of Fe (ill) in washing solutions. Under these conditions, V (IV) does not bind into an inert complex and is titrated together with Fe (III) ions at pH 1-2 with a solution of EDTA. Increasing the concentration of NHt to} k 3.7 M leads to obtaining saturated relative to NH ions. solution. When the solution was boiling for less than 5 minutes, the results were overestimated (20 mg of Fe was introduced, 23 mg was determined). This can be explained by the fact that M0 does not have time to decompose to VOj-, in connection with which the completeness of binding V (W) to the complex is not achieved. V (V) is titrated together with Fe (I1). More than 15 minutes of boiling will increase the duration of the analysis. By the proposed method samples were analyzed during wastewater treatment. Example 1. Determination of Fe (III) in sediments after wastewater treatment from vanadium. 0.1000 g of a sample containing 2-5% V (IV) is weighed with an error of no more than 0.0002 g, placed in a 200 ml beaker, moistened with water, 4 ml (1: 1) are poured in and dissolved by heating, Do not allow baking. After complete decomposition of the sample, the solution is transferred to a conical flask with a capacity of 500 ml, neutralized with 24% NaOH to pH 10 (universal indicator paper), a single excess of V (IV) relative to V (IV) is added, and water is added to 200 ml , heated to 80 ° C, added MnlS to a concentration of 0.5 M (5 g MNdSP and kept at this temperature for 15 minutes. After cooling, the precipitate was dissolved in HCl (1: 1), allowing one or two drops of excess. Check pH solution on indicator paper (pH must be equal to 2), heated to 4550, 10-12 drops of sulfosalicylic acid are added and An example of determination of Fe (HI) - in sediments (after vanadium sewage treatment) 0.1000 g of sample containing 2-5% V (IV), weighed with an error not

more than 0.0002 g, placed in a glass with a capacity of 200 ml, moistened with water, poured 4 ml (1: 1) and dissolved by heating, not allowing boiling.

After complete decomposition of the sample, the solution is transferred to a conical flask with a capacity of 500 ml, neutralized with 24% NaOH to pH 14 (universal indicator paper), a fivefold excess of V (V) relative to V (IV) is added, and water is added to 200 ml .

The results of determination of re () in model solutions containing V (IV) and V (V) with a volume of V 200 ml, M, complexation pH 10, pH titration 1,

1: 1: 0 1: 3: 0 1: 2: 0 1: 1: 1 1: 3: 3 1: 2: 5 1: 1: 6 1: 1: 7 1: 1: 10 you

Defined Fe (U),%, x in the ways:

heat to 100 ° C, add NH4C1 to a concentration of 3.7 M (37 g MNDS) and boil for 5 minutes. After cooling, the precipitate is dissolved in HC1 (1; 1-), allowing one to two drops of excess. The pH of the solution is checked to indicator paper (the pH should be 2), heated to 45-50, 1012 drops of sulfosalicylic acid are added and titrated with a solution of complexone 1 (1 before the color changes from wine red to pure green.

Table 1

25.59 27.11 27.84 21.80 22.41 29.89 25.92 25.40 27.56 Tab. Figure 1 presents the resultant solutions containing V (IV) and V (v), determinations of Fe (41) in model 45 at various ratios. The results of the determination of Fe (III) in the sediments after sewage treatment, weighed 0.1 g, volume 200 ml, Table 2

. Determined Fe (III),%, x in the ways:

Claims (2)

Static processing: S rep. (1) 0.14; S play (2) 0.13; t comp. In tab. Figure 2 shows the results of the determination of Fe (HI) by the most advanced and combined methods. The advantages of the proposed method are: an increase in the accuracy of the determination of iron in the analyzed object for eliminating the operation of separating iron in the form of hydroxide by the prototype, since the separation may lead to loss of the main substance and coprecipitation of impurities; simplification of the conditions for determination of iron by eliminating the operations of precipitation, filtering, washing and dissolving the precipitate and, as a consequence, reducing the duration of the analysis (from 6 to 1.5 hours). Claim 4.SPOSOC6 complexonometric determination of iron (P1) in vanadium-containing samples, including their dissolution in sulfuric acid and Continued table. 2 t 0.05 (4) 2.78 The subsequent titration of iron with ethylenediaminetetraacetic acid at pH 1-2 in the presence of an indicator, characterized in that, in order to simplify and improve the determination accuracy by eliminating the interfering effect of vanadium (W), Before titration, a 1–5-fold excess of vanadium (V) is introduced into the solution with respect to vanadium (W) at pH 10–14 and 0.5–3.7 m of ammonium salt solution. 2. The method according to p. 1, about tl and -: that the solution with a pH of 10-14 is kept at 80-100 s for 5-15 minutes. Sources of information taken into account in the examination 1.Faynberg S.Yu. and Filippova N.A. Analysis of ores of non-ferrous metals. Moscow, Scientific and Technical Publishing House for Ferrous Metallurgy, 1963, p. 414-430. 2.Shvartseabah G. and Flashka G. Complexometric titration. M., Himi, 1970, p. 212 (prototype).