SU899479A1 - Method for detecting vanadium (iii) - Google Patents

Description

The invention relates to analytical chemistry of vanadium and can be used to determine V (III) with the simultaneous presence of V (tv) and V (V) B channel catalyzers, minerals, reagents. A known method for determining vanadium involves treating a sample by heating it with a mixture of concentrated phosphoric acid and hydrogen peroxide followed by titration of V (tV) with a solution of ferrous oxide salt 1. However, this method is suitable for determining the total (total) content of vanadium V (III) + V (IV) V (V) and cannot be used to determine the content of trivalent vanadium. The closest to the proposed technical essence and the achieved result is the method of determining V (III) and V (IV), which includes processing the sample in condensed phosphoric acid during heating followed by redox titration of trivalent and quadravalent vanadium 23. However, this method not suitable for determining V (III) if it is accompanied by V () V) and V (V), since, when the sample is dissolved, VW) interacts with V (III) to form V (iv). The purpose of the invention is to determine the content of trivalent vanadium with the simultaneous presence of four and pentavalent vanadium. The goal is achieved by treating the initial sample containing three-, four-, and five-vanadium vanadium in a medium of condensed phosphoric acid (, 85-t. E g / cm) with potassium feoicyanicide at a temperature of 50-60 ° C, followed by titration of the reducing agent. The curve shows a potentiometric titration curve of a thief after processing a sample of potassium ferricyanide in condensed phosphoric acid. In the environment of condensed phosphoric acid (CPA), the oxidative capacity of potassium ferricyanide is much higher than the oxidative capacity of V (V), which determines the choice of this reagent as oxide V (III). When the temperature of the solution increases from 20 to 20, the content of ferricyanide does not change, since it is stable. The stability of KjFe (CN) l in an acidic medium is associated with (the inertness of this complex. With an increase in temperature above, partial destruction of K, Fe (CN) J is observed. Thus, a factor limiting the upper (60 s) temperature limit of the sample containing V (III), V (IV) and V (V) is the decomposition of K. Fe (CN) l. At temperatures below, the duration of dissolution of the sample increases. On the basis of the data obtained, the optimal temperature range for sample processing 50- 60 ° С, in which all three valence forms of vadi are stable. In the case of CPK, they quantitatively interact with V (I1) to form V (iv), it does not interact with V (V). To clarify the possibility of using potassium ferricyanide to determine V (IO in the presence of V (v), the following experiments are performed, To solutions V (HI) in CPK is added a mixture of known quantities of V (V) and potassium ferricyanide in CPK, mixed and the concentration of unreacted (CM) 1 and formed V (IV) is determined by known potentiometric methods. Potassium ferricyanide is introduced in a 5-10 fold excess relative to V (V). The content of V (I1) is controlled by the number of formed V (tv) and by the amount of reacted (CN) 3. The results of the determination of V (III) in the presence of V (V) are presented in Table. 1. In table. Figure 2 shows the results of the determination of V (fll) in the spent samples of vanadium catalysts of type 8KCC, containing AOIs), V (V), and V (V). As can be seen from the table. 1, V (M |) quantitatively interacts with (CN while V (v) reacts with V (O is not consumed, 8 4 When analyzing samples containing (III), V OC) and V (U), with simultaneous presence, the V (ill) content is calculated only by the amount of the unreacted ferricyanide, aka V (iv). formed from V (which is added to the V (iv) contained in the sample. As can be seen from Table 2, the proposed method provides obtaining reproducible V (III) determination results in the presence of V (IV) and M (V). The definition time of V (P1) is 30–35 minutes. Example: The definition of V (w) in the catalyst contains V (iv) V (V) is carried out as follows: A portion of finely grated catalyst — 0.1 g is placed in a beaker, 30 ml (CPC) is added with a density of 1.87 g / cm (prepared by thermal dehydration of orthophosphoric acid xch a) containing 2 ml of 0.1 N solution of potassium fer- pericyanide solution and maintain the solution in a thermostat at 50 ° C for 10 minutes, 15 ml of water are poured and titrated with 0.05 N. Mora’s salt solution by a potentiometric method with a platinum electrode system chlorine silver. The Mohr salt solution is standardized under the same conditions for potassium dichromate. The 1st jump on the curve corresponds to the end of the titration of ferricyanide unreacted with V (g) (the end point of the titration (kt, 1) and the content of V (br) is calculated by it, V (n) was found by the proposed method 0.58% , known - 0.62, the proposed method allows the definition of V (III) in the presence of V (IV) and V (V) under normal conditions, without recourse to oxygen from the air and long-term operations for the separation of V (III a) or eliminating the interfering influence of (v) and v (w); in addition, from the same portion of the solution used to determine v (iii) the proposed method m, in addition, V (IV) and V (V) can be determined. total V (IV) by a known method. The content of V (IV) in the samples can be calculated from the difference between the amount of Mohr salt, spent on achieving, respectively, and potential jumps minus the content of V (III).

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The content of V (V) is calculated. Thus, it is possible to differentiate the volumes of the spent definition of V / (n () i V (V) to achieve AND and I jumps of potential- and V (IV), which greatly simplifies the analysis of la compared with known methods.

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Claims (1)

Claim A method for the determination of vanadium (HI), including processing the sample in a condensed phosphoric acid medium when heated, followed by titration with ferrous iron salt, characterized in that, in order to enable analysis of vanadium (III) in the presence of tetravalent vanadium, processing 899 ** 79 12 samples are carried out in the presence of potassium ferricyanide at a temperature of 506 ° C.