GOST 19251.7-93

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  ГОСТ 19251.7-93

GOST 19251.7−93 Zinc. Methods for determination of aluminium

GOST 19251.7−93

Group B59

INTERSTATE STANDARD

ZINC

Methods for determination of aluminium

Zinc. Methods of aluminium determination

OKS 77.120
AXTU 1709

Date of introduction 1997−01−01

Preface

1 DEVELOPED by Eastern research mining and metallurgical Institute of nonferrous metals (VNIItsvetmet)

INTRODUCED by Gosstandart of the Republic of Kazakhstan

2 ADOPTED by the Interstate Council for standardization, Metrology and certification of March 15, 1994 (Report No. 1 map)

The adoption voted:

3 Decree of the Russian Federation Committee on standardization, Metrology and certification dated June 19, 1996, No. 387 interstate standard GOST 19251.7−93 introduced directly as state standard of the Russian Federation from January 1, 1997

4 INTRODUCED FOR THE FIRST TIME

1 SCOPE

This standard applies to zinc grades CV, CV0, C0A, C0, C1, C2 according to GOST 3640 and sets the atomic absorption and photometric methods for the determination of aluminum content in the range of mass fraction from 0.002 to 0.03%.

2 NORMATIVE REFERENCES

The present standard features references to the following standards:

GOST 199−78 Sodium acetate 3-water. Specifications

GOST 3118−77 (ST SEV 4276−83) hydrochloric Acid. Specifications

GOST 3640−94 Zinc. Specifications

GOST 3760−79 (ST SEV 3858−82) aqueous Ammonia. Specifications

GOST 4217−77 (ST SEV 1697−79) Potassium nitrate. Specifications

GOST 4234−77 Potassium chloride. Specifications

GOST 4461−77 (ST SEV 3855−82) nitric Acid. Specifications

GOST 9849−86 iron Powder. Specifications

GOST 10929−76 (ST SEV 5768−86) Hydrogen peroxide. Specifications

GOST 14261−77 hydrochloric Acid of high purity. Specifications

GOST 19251.0−79 Zinc. General requirements for methods of analysis

GOST 19908−90 Crucibles, bowls, beakers, flasks, funnels, test tubes and caps made of transparent quartz glass. General specifications

GOST 23957.1−80 Zinc. Method of atomic-absorption determination of lead, cadmium and antimony

GOST 24147−80 aqueous Ammonia of high purity. Specifications

GOST 25336−82 (ST SEV 2945−81, ST SEV 4023−83, ST SEV 4975−85, ST SEV 4976−85) Glassware and laboratory equipment made of glass. The types, basic parameters and dimensions

GOST 27068−86 (ST SEV 223−85) Chernovetskiy Sodium (sodium thiosulfate) 5-water. Specifications

3 GENERAL REQUIREMENTS

General requirements for methods of analysis GOST and GOST 19251.0 23957.1*.
_______________
* Standards 23957.1−2003. — Note the CODE.

4 SAFETY REQUIREMENTS

Safety requirements — according to GOST and GOST 23957.1 19251.0.

5 ATOMIC ABSORPTION METHOD

The method is based on measurement of the absorption of the analytical line of aluminium 309,3 nm with the introduction of the sample solution and compare solutions in the flame acetylene — nitrous oxide.

Sample of zinc was transferred into solution by acid decomposition.

In the determination of aluminium in the range of mass fraction from 0.01 to 0.03% photometric solutions obtained directly after dissolution the sample in acid; in determining the in the range of mass fraction from 0.002 to 0.01% aluminium is pre-concentrated by precipitation on iron hydroxide.

5.1 Equipment, reagents and solutions

Spectrophotometer, atomic absorption, and any brand with a radiation source for aluminium.

Air, compressed under a pressure of 2·10-6·10PA (2−6 ATM) depending on the device.

The flat-bottomed or conical flask with a capacity of 200−250 cm, and the glasses are made of heat-resistant or chemically resistant glass with a capacity of 250−400 cm — GOST 25336.

Acetylene in cylinders.

Nitrous oxide in cylinders.

Filters obestochennye blue ribbon [1].

Nitric acid — according to GOST 4461 and diluted 1:3, 1:1.

Hydrochloric acid — according to GOST 3118 and diluted 1:1.

Ammonia water according to GOST 3760, diluted 1:1,5.

Hydrogen peroxide — according to GOST 10929.

Iron powder restored brand MLB-1 — according to GOST 9849.

The solution of iron: 0.5 g of iron dissolved in 50 cmhydrochloric acid with a few drops of nitric acid (1:3), transferred to a volumetric flask with a capacity of 500 cm, was adjusted to the mark with water and mix. 1 cmof solution contains 10 mg of iron.

Aluminium metal granulated in [2].

Potassium chloride — according to GOST 4234, a solution of 191 g/DM.

Potassium nitrate — GOST 4217, a solution of 260 g/DM.

Standard solutions and solutions comparison:

Standard solution A: 1,000 g of metallic aluminium is dissolved in 50 cmof hydrochloric acid under heating, cooled, transferred into a measuring flask with volume capacity of 1000 cm, adjusted to the mark with water and mix. 1 cmof the solution contains 1,000 mcg of aluminum.

Standard solution B: 10 cmsolution And placed in a volumetric flask with a capacity of 100 cm, adjusted to the mark with water and mix. 1 cmof the solution contains 100 micrograms of aluminium.

Standard solution: 10 cmof solution B is placed in a volumetric flask with a capacity of 100 cm, adjusted to the mark with water and mix. 1 cmof solution contains 10 mcg of aluminum.

Solutions comparison: in a volumetric flask with a capacity of 100 cmmeasured by pipette standard solutions B and C according to table 1.


Table 1 — Preparation of solutions comparison

The solutions comparison is prepared in two series:

I series — in each of the volumetric flasks was added 3 cmof a solution of nitrate of potassium, and 6 cmof nitric acid (1:1), dilute to the mark with water and mix;

II series — in each of the volumetric flasks was added 3 cmof potassium chloride solution, 2 cmof a solution of iron and 30 cmof a hydrochloric acid solution, dilute to the mark with water and mix.

5.2 analysis

5.2.1 Determination of aluminium in the range of mass fraction from 0.01 to 0.03%

The weight of zinc weight of 1,000 g was placed in a conical flask or beaker with a capacity of 200−250 cm, flow 15 cmof nitric acid (1:3) and dissolved by heating. The solution is cooled, add 1.5 cmof a solution of potassium nitrate, transferred to a volumetric flask with a capacity of 50 cm, adjusted to the mark with water and mix.

Analyzed solutions and solutions comparison I series is sprayed into the flame nitrous oxide — acetylene and measure the absorption of the analytical line of aluminium 309,3 nm.

Measurement conditions selected in accordance with device used. For spectrophotometers with modes of «concentration» and «absorption» work mode «concentration» and then the result get on the scoreboard in µg/cm, or in the mode «absorption» method «limiting solutions» or calibration schedule. For spectrophotometers that have the mode «absorption», working in this mode, the method of «limiting solutions» or calibration schedule.

5.2.2 Determination of aluminium in the range of mass fraction from 0.002 to 0.01%

The weight of zinc weight of 5,000 g was placed in a beaker with a capacity of 400 cmand dissolved in 50 cmof nitric acid (1:1) without heating, add 1 cmof hydrogen peroxide, dilute with water to volume of about 120 cm, add 1 cmof solution of iron and poured 90 cmof ammonia solution, mixing the sample with a glass rod. Heated the solution on the cooker to coagulate the precipitate. After 15 — 20 min the sample was filtered through a dense filter (blue ribbon). Glass, which had a precipitation of hydroxides, and the filter cake washed once with water. The filter cake is dissolved in 15 cmof a hydrochloric acid solution (1:1) heated to 70−90 °C, pre-wash it with a solution of glass, which carried out the precipitation of the hydroxides. Collect the solution in a volumetric flask with a capacity of 50 cm, which had previously placed 1.5 cmof potassium chloride solution, adjusted to the mark with water and mix.

Analyzed solutions and solutions comparison II series spray into the flame nitrous oxide — acetylene and measure the analytical absorption lines of aluminum. The conditions of measurement according to 5.2.1.

5.3 Processing of results

5.3.1 Mass fraction of aluminum , %, is calculated by the formula

, (1)

where is the mass concentration of aluminum in the sample solution, found by calibration schedule or by «limiting solutions», µg/cm;

 — the volume of the analyzed solution, cm;

 — weight of zinc,

5.3.2 allowable Absolute differences (%) the results of two parallel measurements (a measure of repeatability) and the results of two tests (a measure of reproducibility) with the confidence coefficient =0.95 does not exceed permissible values, specified in table 2 (determination of aluminium in 5.2.2) and schedule 3 (determination of aluminium in 5.2.1).


Table 2 — allowable Absolute differences

Percentage

Table 3 — allowable Absolute differences

Percentage

Allowable absolute difference for the intermediate mass fraction of aluminium calculated using linear interpolation.

6 PHOTOMETRIC METHOD

The method is based on formation of colored complex compounds of aluminum, chromazurol C (S) at pH=5,7−5,8 and measuring its optical density at a wavelength of 590 nm. The interfering influence of iron eliminate recovery of ascorbic acid; copper is masked with sodium thiosulfate.

6.1 Equipment, reagents and solutions

Spectrophotometer or photoelectrocolorimeter of any kind for measurements in the visible region of the spectrum.

Flask of quartz — GOST 19908 capacity of 250 cm.

Nitric acid — according to GOST 4461.

Hydrochloric acid — according to GOST 14261, diluted 1:1, 1:3 and a solution of 0.1 mol/DM.

Ascorbic acid, a solution of 10 g/DM, freshly prepared.

Ammonia water according to GOST 24147, diluted 1:10.

Chernovetskiy sodium (sodium thiosulfate) — according to GOST 27068, a solution of 50 g/DM, freshly prepared.

Sodium acetate — GOST 199, a solution of 2 mol/DM.

Chromazurol S (S) — [3], a solution of 1 g/DM.

Paper universal indicator — [4].

Zinc — according to GOST 3640, brand CV00.

A solution of zinc: 5,000 g of zinc is dissolved by heating in 70 cmof hydrochloric acid (1:1) add 6−7 drops of nitric acid. The solution was evaporated to wet salts. The residue is dissolved in water, transferred to a volumetric flask with a capacity of 500 cm, was adjusted to the mark and mix. 1 cmof solution contains 10 mg of zinc.

Aluminium metal granulated in [2].

Standard solutions of aluminium:

Solution a: 0,100 g of aluminium is dissolved by heating in 50 cmof hydrochloric acid (1:3), cooled, transferred into a measuring flask with volume capacity of 1000 cm, adjusted to the mark with water and mix. 1 cmof solution A contains 0.1 mg of aluminium.

Solution B: 10 cmsolution And placed in a volumetric flask with a capacity of 100 cm, adjusted to the mark with water and mix. 1 cmof a solution contains 0.01 mg of aluminum.

Solution: 10 cmof solution B is placed in a volumetric flask with a capacity of 100 cm, adjusted to the mark with water and mix. 1 cmof the solution contains 0.001 mg of aluminium.

Solutions B and C prepared on the day of application.

6.2 analysis

6.2.1 a sample of zinc with a mass of 0,500 g was placed in a quartz conical flask with a capacity of 250 cmand dissolved by heating in 10 cmof hydrochloric acid (1:1) add 6−7 drops of nitric acid. The solution was evaporated to wet salts. The residue is dissolved in water, transferred to a volumetric flask with a capacity of 100 cm, is diluted to the mark with water and mix.

Aliquot part of the solution was 10 cm(with a mass fraction of aluminium is up to 0.01%) or 2 cm(for the mass concentration of aluminum in excess of 0.01%) were placed in a glass with a capacity of 50 cm, add 2 cmof ascorbic acid solution and carefully neutralized with ammonia (1:10) to pH=5 by universal indicator paper. The solution was transferred to a volumetric flask with a capacity of 50 cm, is diluted with water to a volume of approximately 25 cm, add 1.5 cmof sodium thiosulfate, washed the walls of the flask with water, pour 2.5 cmof a hydrochloric acid solution 0.1 mol/l, 1.0 cmof a solution of chromazurol C (S), 2.5 cmof a solution of sodium acetate, stirring the solution after addition of each reagent. Dilute to the mark with water and mix.

After 10 minutes measure the optical density of the solution on the spectrophotometer or photoelectrocolorimeter at a wavelength of 590 nm in a cuvette with the thickness of the light absorbing layer 50 mm Solution serves as a comparison solution containing the same amounts of ascorbic acid, sodium thiosulfate, hydrochloric acid, chromazurol C (S) and sodium acetate. Simultaneously with the analysis carried out control and experience with all applicable in the analysis of the reagents and under the same conditions. The aluminum content in the calibration set g

the Rafiki.

6.2.2 For constructing the calibration graphs in glasses with a capacity of 50 cmis placed 0, 1, 2, 3, 4 and 5 cmof solution, which corresponds to 0, 1, 2, 3, 4 and 5 g of aluminum, add 5 cmof a solution of zinc (at a mass fraction of aluminium is up to 0.01%) or 1 cmof a solution of zinc (at a mass proportion of aluminum of more than 0.01%) and add 2cmof a solution of ascorbic acid and then do as described in 6.2.1.

According to the obtained values of optical density of the solutions and the corresponding content of the aluminium build of the calibration graphs.

6.3 Processing of results

6.3.1 Mass fraction of aluminum , %, is calculated by the formula

, (2)

where is the mass of aluminum was found in the calibration schedule, mcg;

 — volume of initial solution, cm;

 — the mass of the zinc sample, g;

 — volume aliquote part of the solution, cm.

6.3.2 allowable Absolute differences (%) the results of two parallel measurements (a measure of repeatability) and the results of the two analyses (the indicator of reproducibility) with the confidence coefficient =0.95 does not exceed the permissible values given in table 4.


Table 4 — allowable Absolute differences

Percentage

Allowable absolute difference for the intermediate mass fraction of aluminium calculated using linear interpolation.

Annex a (informative). BIBLIOGRAPHY

APPENDIX A
(reference)

1 TU 6−09−1678−86 Filters obestochennye blue ribbon

2 TU 6−09−3742−87 Aluminium granulated h. d. a., h

3 6−09−05−1175−82 THAT the Chromazurol S (S)

4 TU 6−09−1181−89 Paper universal indicator