GOST 3240.21-76

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  ГОСТ 3240.21-76

GOST 3240.21−76 magnesium Alloys. Method for the determination of beryllium (with Change No. 1)

GOST 3240.21−76

Group B59

INTERSTATE STANDARD

MAGNESIUM ALLOYS

Method for the determination of beryllium

Magnesium alloys.
Method for determination of beryllium

ISS 77.120.20
AXTU 1709

Date of introduction 1978−01−01

INFORMATION DATA

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

2. APPROVED AND promulgated by the Decree of the State Committee of standards of Ministerial Council of the USSR from 28.12.76 N 2889

3. REPLACE GOST 3240−56, section IX of the determination of beryllium

4. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

5. Limitation of actions taken by Protocol No. 2−92 of the Interstate Council for standardization, Metrology and certification (ICS 2−93)

6. EDITION with Change No. 1, approved in June 1987 (IUS 11−87)


This standard establishes a fluorescent method for the determination of beryllium (with a mass fraction of from 0.0001 to 0.015%).

The method is based on formation of complex of beryllium with by Maureen at pH 13, a fluorescent green color. The maximum absorption spectrum of beryllium complex is about 430−440 nm, and maximum emission range of about 530 nm. Therefore, when you use. to measure the fluorescence intensity should excite the fluorescence with light from incandescent bulbs.

1. GENERAL REQUIREMENTS

1.1. General requirements for method of analysis according to GOST 3240.0.

2. APPARATUS, REAGENTS AND SOLUTIONS

Fluorimeter type KFL-2−1 or ISP 51Ф with the prefix FEP-1 illuminator type ОИ18.

Hydrochloric acid according to GOST 3118, diluted 1:1.

Nitric acid according to GOST 4461.

Sodium hydroxide according to GOST 4328, 20% solution.

The mixture of complexing agent; is prepared as follows: 500 cmof water successively dissolved (after addition of each reagent must be well mixed) 5 g of sodium pyrosulfite according to GOST 26838, 12.5 g of ascorbic acid, 12.5 g citric acid according to GOST 3652, 75 g Trilon B according to GOST 10652 and 60 cmof 20% aqueous solution of sodium hydroxide. The mixture was heated until complete dissolution of all salts and filtered. Apply the mixture freshly made.

Alizarin blue, 0,1% solution; prepared as follows: 0.1 g of the reagent dissolved in a mixture of 80 cmof ethyl alcohol according to GOST 5962* and 20 cmof water.
________________
* On the territory of the Russian Federation GOST R 51652−2000.

A buffer solution with a pH of 13; prepared as follows: 28,60 g of boric acid according to GOST 9656 dissolved in 500 cmof hot water, poured into a volumetric flask with a capacity of 1 DM, is added sodium hydroxide (solution of 96 g per 400 cmof water), dilute to the mark with water, mix well and check the pH of the solution.

Maureen, solution: is prepared as follows: 0.02 g of reagent was dissolved in 100 cmdistilled ethyl alcohol.

Standard solution of beryllium; prepared as follows: 0,2800 g of beryllium is dissolved in 30 cmof hydrochloric acid and dilute the solution to 1 DMwith water. On the day of use dilute the solution 100 times and get solution with a content of beryllium is 0.001 mg/cm.

Primary magnesium ingots according to GOST 804 in the form of chips.

3. ANALYSIS

3.1. A portion of the alloy (tab.1) is placed in a beaker with a capacity of 300 cm, is dissolved in 20 cmof hydrochloric acid diluted 1:1, oxidized 3−5 drops of nitric acid and the solution evaporated to a small volume and removal of nitrogen oxides. The solution is transferred to a measuring flask with volume capacity in accordance with table.1, dilute to the mark with water and mix. Select aliquot part of the solution is 2 cmand transferred to a volumetric flask with a capacity of 100 cm, then add 25 cmof hot mix complexing reagent, 30 drops of alizarin blue and neutralized with 20% sodium hydroxide solution until a green color. Then add 25 cmbuffer solution, 1 cmof the Morin solution, made up to the mark with water and mix. After 10 minutes measure the fluorescence on the instrument in a cuvette with a layer thickness of 3 cm of beryllium find in the calibration schedule.

Table 1

3.2. Construction of calibration curve

In five glasses with a capacity of 300 cmwas placed 1 g of magnesium, add 1,0; 3,0; 5,0; 7,0 and 9,0 cmstandard solution of 0.001 mg/cm, which corresponds to: 0,001; 0,003; 0,005; 0,007 and 0.009 g of beryllium. The sixth glass is a standard solution not added, it is used for the reference experiment. The mixture was dissolved and further analysis is carried out as specified in clause 3.1. According to the obtained values of the fluorescence intensity calibration curve built excluding readings of control experience.

(Changed edition, Rev. N 1).

4. PROCESSING OF THE RESULTS

4.1. Mass fraction of beryllium (a) percentage calculated by the formula

,

where is beryllium found on the calibration schedule g;

 — volume of initial solution, cm;

 — volume aliquote part of the original solution, cm;

 — the weight of the portion of alloy,

4.2. Allowable absolute differences of the results of the parallel definitions should not exceed the values given in table.2.

Table 2

5. CONTROL OF MEASUREMENT ACCURACY

To control the accuracy of measuring the mass fraction of beryllium from 0.0001 to 0.015% using state standard samples of magnesium alloys, as well as industry standard samples and standard samples of the enterprise of magnesium alloys, issued in accordance with GOST 8.315. Accuracy control measurement is carried out in accordance with GOST 25086.

Allowed to control the accuracy of measuring the mass fraction of indium by the method of additions.

Sec. 5. (Added, Rev. N 1).