GOST 19863.3-91

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  ГОСТ 19863.3-91

GOST 19863.3−91 Alloy of titanium. Method for the determination of chromium and vanadium

GOST 19863.3−91

Group B59

STATE STANDARD OF THE USSR

ALLOYS OF TITANIUM

Method for the determination of chromium and vanadium

Titanium alloys.
Method for the determination of chromium and vanadium Corporation

AXTU 1709

Date of introduction 1992−07−01

INFORMATION DATA

1. DEVELOPED AND INTRODUCED by the Ministry of aviation industry of the USSR

DEVELOPERS

V. G. Davydov, doctor of engineering. Sciences; V. A. Moshkin, PhD. tech. Sciences; G. I. Friedman, PhD. tech. Sciences; L. A. Tenyakova, A., Korolyov

2. APPROVED AND put INTO EFFECT by Decision of the USSR State Committee on management of quality and standards from 05.05.91 N 625

3. REPLACE GOST 19863.3−80

4. The frequency of inspection — 5 years

5. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

This standard specifies the titrimetric method for the determination of chromium and vanadium in the joint presence (when the mass fraction of chromium of from 0.1 to 2.0% and the mass fraction of vanadium from 0.1 to 6.0%).

1. GENERAL REQUIREMENTS

1.1. General requirements for methods of analysis GOST 25086 with the Supplement.

1.1.1. For the results analysis be the arithmetic mean of results of two parallel measurements.

2. THE ESSENCE OF THE METHOD

The method is based on dissolving the sample in a mixture of sulfuric and bridgestation acids, the oxidation of vanadium to pentavalent with potassium permanganate and titration it with a solution of salt Mora with phenylanthranilic acid as an indicator, the oxidation of chromium to hexavalent neccersarily ammonium in the presence of a catalyst of silver nitrate and the titration amounts of vanadium and chromium with a solution of salt Mora with phenylanthranilic acid as indicator.

3. APPARATUS, REAGENTS AND SOLUTIONS

Drying oven with thermostat.

Sulfuric acid according to GOST 4204 density 1.84 g/cm, mortar 1:1 and 1:5.

Nitric acid according to GOST 4461 density of 1,35−1,40 g/cm.

Boric acid according to GOST 9656.

Hydrofluoric acid according to GOST 10484.

Acid bridgestation: 280 cmhydrofluoric acid at a temperature of (10±2) °C add portions 130 g of boric acid and stirred. The reagent is prepared and stored in a plastic container.

Ammonium neccersarily according to GOST 20478, a solution of 250 g/DM.

Silver nitrate according to GOST 1277, a solution of 1 g/DM.

Oxalic acid according to GOST 22180, a solution of 10 g/DM.

Potassium permanganate according to GOST 4233, solution 100 g/DM.

Sodium carbonate according to GOST 83.

Acid N-phenylanthranilic on the other 6−09−3501, a solution of 2 g/DM: 0.2 g of sodium carbonate were placed in a glass with a capacity of 100 cm, was dissolved with heating in 50 cmof water, add 0.2 g phenylanthranilic acid, stirred and cooled to room temperature and add water to 100 cm.

Potassium dichromate according to GOST 4220, solutions of 0.1 and 0.02 mol/DM: 29,42 or 5.88 g of recrystallized potassium dichromate is placed in a measuring flask with volume capacity of 1000 cm, dissolved in 500 cmof water, made up to the mark with water and mix.

For recrystallization 100 g of potassium dichromate were placed in a glass with a capacity of 400 cm, 150 cm pour thewater and dissolved by heating. The solution with vigorous stirring pour in a thin stream in a porcelain Cup, which is cooled with ice water. Precipitated crystals filtered off by suction on a funnel with a porous glass plate, dried for 2−3 hours at temperature (102±2) °C, crushed, and finally dried at a temperature of (200±5) °C for 10−12 h

Salt of protoxide of iron and ammonium double sulfate (salt Mora) according to GOST 4208, solutions of 0.1 and 0.02 mol/DM: 39,5 or 7.9 g of salt Mora is placed in a beaker with a capacity of 800 cmand dissolved in 500 cmof water, poured 100 cmof sulfuric acid solution 1:1, cooled to room temperature, transferred into a measuring flask with volume capacity of 1000 cm, made up to the mark with water and mix.

Mass concentration solution of salt Mora (practical) expressed in g/cm(chrome), calculated according to the formula

, (1)

where 0,001733 mass concentration of salt solution Mora (theoretical), expressed in g/cmchrome;

 — the relationship between solutions of potassium dichromate and salt Mora.

Set the ratio between the solutions of potassium dichromate and salt Mora: three conical flasks with a capacity of 250 cmtransfer pipette at 10 cmof a solution of potassium dichromate 0.1 or 0,02 mol/land diluted to 100 cmwith water, poured 20 cmof sulfuric acid solution 1:5, mix, add 5−6 drops of a solution phenylanthranilic acid and titrate with the appropriate solution of salt Mora before moving blue-purple color of the solution green.

, (2)

where is the volume of potassium dichromate solution used for titration, cm;

 — the volume of salt solution Mora, used for titration, sm.

The mass concentration of salt solution Mora set before use.

Mass concentration solution of salt Mora (practical) expressed in g/cmvanadium (), calculated by the formula

, (3)

where 0,005095 mass concentration of salt solution Mora (theoretical), expressed in g/cmvanadium.

4. ANALYSIS

4.1. A portion of the sample weighing 1 g is placed in a conical flask with a capacity of 250 cm, and poured 70 cmof sulfuric acid solution 1:5, 2 cmbridgestation acid and heated until complete dissolution.

The solution was added dropwise nitric acid until the disappearance of violet colour, 2−3 drops in excess, and evaporated to the appearance of sulphuric acid fumes. The solution was cooled to room temperature, poured 100 cmof water and dropwise a solution of potassium permanganate until a stable pink color. Then slowly dropwise added a solution of oxalic acid before bleaching.

The solution is titrated with the Mohr salt solution with molar concentration of 0.02 mol/DM(with mass fraction of vanadium less than 0.5%) or 0.1 mol/DM(with mass fraction of vanadium of more than 0.5%) with 5−6 drops of indicator phenylantranilic acid until the solution colour from blue-violet to green.

4.2. The solution is poured 10 cmof silver nitrate, 30 cmsolution naternicola ammonium, the contents of the flask are heated to boiling and boiled until the appearance of violet colouration, indicating complete oxidation of chromium. The solution continue to boil until the termination of allocation of small bubbles. Then add 5 cmof sodium chloride solution and heat the solution until the disappearance of the crimson color.

The solution was cooled to room temperature, titrated with Mohr salt solution with molar concentration of 0.02 mol/DMat a mass fraction of chromium is less than 0.5% or 0.1 mol/DMfor the mass concentration of chromium greater than 0.5% with 5−6 drops of indicator phenylantranilic acid until the solution colour from blue-violet to green.

5. PROCESSING OF THE RESULTS

5.1. Mass fraction of vanadium () in percent is calculated by the formula

, (4)

where is the established mass concentration of salt solution Mora, expressed in g/cmvanadium;

 — the volume of salt solution Mora, used for titration of vanadium, cm;

 — weight of sample, g.

5.2. Mass fraction of chromium () in percent is calculated by the formula

, (5)

where is the established mass concentration of salt solution Mora, expressed in g/cmchrome;

 — the volume of salt solution Mora, used for titration of the amounts of vanadium and chromium, with

m.

5.3. Discrepancies in the results must not exceed the values given in the table.