GOST 19863.12-91

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  ГОСТ 19863.12-91

GOST 19863.12−91 Alloy of titanium. Methods for determination of chromium

GOST 19863.12−91

Group B59

STATE STANDARD OF THE USSR

ALLOYS OF TITANIUM

Methods for determination of chromium

Titanium alloys.
Methods for the determination of chromium

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; M. N. Gorlova, PhD. chem. Sciences; A. I. Korolev, O. L. Sikorska, PhD. chem. Sciences

2. APPROVED AND put INTO EFFECT by Decision of the USSR State Committee on management of quality and standards from 5.05.91 N 626

3. REPLACE GOST 19863.12−80

4. The frequency of inspection — 5 years

5. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

This standard establishes titrimetric (mass fraction in range from 0.1 to 12.0%) and atomic absorption (at a mass fraction from 0.1 to 12.0%) methods for determination of chromium.

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. TITRIMETRIC METHOD FOR THE DETERMINATION OF CHROMIUM

2.1. The essence of the method

The method is based on dissolving the sample in a mixture of sulfuric and bridgestation acids, the oxidation of chromium to hexavalent neccersarily ammonium in the presence of a catalyst of silver nitrate and the titration of chromic acid solution of double sulphate salts of protoxide of iron and ammonium (salt Mora) with phenylanthranilic acid as indicator.

2.2. 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, a solution of 1:1.

Hydrofluoric acid according to GOST 10484.

Boric acid according to GOST 9656.

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.

Manganese (II) sulfate 5-water according to GOST 435.

Sodium chloride 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 was dissolved with heating in 50 cmof water, add 0.2 g phenylanthranilic acid and add water to 100 cm.

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

2.3. Analysis

2.3.1. A portion of the sample weight in accordance with table.1 is placed in a conical flask with a capacity of 250 cm, flow 60 cmof sulfuric acid solution 1:5, 2 cmbridgestation acid and heated until complete dissolution.

Table 1

The solution was added dropwise a solution of nitric acid until the disappearance of violet colour and heated to boiling for 3 min. Then gently poured 100 cmof water, 3−4 drops of solution of sulphate of manganese (II), 10 cmof a solution of silver nitrate and 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 and titrated with a solution of salt Mora and 0.02 mol/DM(with mass fraction of chromium is less than 0.5%) or 0.1 mol/DM(with mass fraction of chromium of more than 0.5%) with 5−6 drops of indicator phenylantranilic acid until the solution colour from crimson to green.

2.4. Processing of the results

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

, (3)

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

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

 — weight of sample, g.

2.4.2. Discrepancies in the results must not exceed the values given in table.2.

Table 2

3. ATOMIC ABSORPTION METHOD FOR THE DETERMINATION OF CHROMIUM

3.1. The essence of the method

The method is based on dissolving the sample in hydrochloric and bridgestation acids and measuring atomic absorption of chromium at a wavelength of 357,9 nm in a flame acetylene — nitrous oxide.

3.2. Apparatus, reagents and solutions

Spectrophotometer of atomic absorption with a radiation source for chromium.

Acetylene according to GOST 5457.

Hydrochloric acid according to GOST 3118 density of 1.19 g/cm, mortar is 2:1 and 1:1.

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

Hydrofluoric acid according to GOST 10484.

Boric acid according to GOST 9656.

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

Ammonium chloride according to GOST 3773, solution 100 g/DM.

Titanium sponge according to GOST 17746* stamps TG-100.
_______________
* On the territory of the Russian Federation GOST 17746−96. — Note the manufacturer’s database.

A solution of titanium 10 g/DM, 1 g of titanium was placed in a conical flask with a capacity of 250 cm, add 80 cmof a hydrochloric acid solution of 2:1, 4 cmbridgestation acid and dissolved with moderate heating. After dissolution, the sample is added twenty drops of nitric acid and boil the solution for 1 min. the Solution was cooled to room temperature, transferred to a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

Chrome according to GOST 5905* brand X00.
______________
* On the territory of the Russian Federation GOST 5905−2004. — Note the manufacturer’s database.

Standard solutions of chromium

Solution a: 1 g of chromium metal was dissolved in 50 cmof hydrochloric acid. The solution was cooled to room temperature, transferred to a volumetric flask with a capacity of 500 cm, made up to the mark with water and mix.

1 cmstandard solution contains 0.002 grams of chromium.

Solution B: 10 cmsolution And placed in a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

1 cmstandard solution B contains from 0.0002

g chrome.

3.3. Analysis

3.3.1. A portion of the sample mass according to table.3 is placed in a conical flask with a capacity of 100 cm, flow 20 cmof a hydrochloric acid solution of 2:1, 1 cmbridgestation acid and dissolved with moderate heating.

Table 3

After dissolution of the sample add 3−5 drops of nitric acid and boil the solution for 1 min. the Solution was cooled to room temperature, transferred to a volumetric flask with a capacity according to table.3, a solution of hydrochloric acid 1:1 solution of ammonium chloride in accordance with table.3, made up to the mark with water and mix.

3.3.2. When the mass fraction of chromium of from 5.0 to 12.0% aliquot part of the solution is equal to 20 cm, taken in a volumetric flask with a capacity of 100 cm, add 2 cmof hydrochloric acid of 1:1, 10 cmof a solution of ammonium chloride, made up to the mark with water and mix.

3.3.3. The solution in the reference experiment is prepared according to claim.3.3.1 and 3.3.2.

3.3.4. Construction of calibration curve

3.3.4.1. When the mass fraction of chromium of from 0.1 to 1.0%

In six volumetric flasks with a capacity of 100 cmpour 20 cmof a solution of Titan, five of them measure 1,0; 2,5; 5,0; 7,5; 10,0 cmstandard solution B, which corresponds to 0,0002; 0,0005; 0,0010; 0,0015; 0.002 g of chromium.

3.3.4.2. When the mass fraction of chromium from 1.0 to 5.0%

In six volumetric flasks with a capacity of 100 cmpour 10 cmof a solution of Titan, five of them measure 2,0; 4,0; 6,0; 8,0; 10,0 cmstandard solution B, which corresponds to 0.0004 inch; 0,0008; 0,0012; 0.0016 inch; 0.002 g of chromium.

3.3.4.3. When the mass fraction of chromium of from 5.0 to 10.0%

Five volumetric flasks with a capacity of 100 cmpour 2 cmof a solution of titanium, four of them measure 5,0; 7,5; 10,0; 12,5 cmstandard solution B, which corresponds to 0.001; 0,0015; 0,002; 0.0025 g of chromium.

3.3.4.4. The solutions in the flasks prepared according to claim.3.3.4.1, 3.3.4.2 and 3.3.4.3, add 2 cmof hydrochloric acid 1:1, 10 cmof a solution of ammonium chloride, made up to the mark with water and mix.

3.3.5. The sample solution, solution control experience and solutions to build the calibration curve is sprayed into the flame of acetylene — nitrous oxide (stoichiometric) and measure the atomic absorption of chromium at a wavelength of 357,9 nm.

According to the obtained values of atomic absorption and corresponding mass concentrations of chromium build a calibration curve in the coordinates «Value of atomic absorption — Mass concentration of chromium, g/cm».

Mass concentration of chromium in sample solution and in the solution of control and experience determined by the calibration schedule.

3.4. Processing of the results

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

, (4)

where is the mass concentration of chromium in the sample solution found by the calibration schedule, g/cm;

mass concentration of chromium in solution in the reference experiment, was found in the calibration schedule, g/cm;

 — the volume of the sample solution, cm;

 — the weight of the portion in the sample solution or in a suitable aliquote part of the sample solution, g

.

3.4.2. Discrepancies in the results must not exceed the values given in table.4.

Table 4