GOST 19709.2-83

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  ГОСТ 19709.2-83

GOST 19709.2−83 Tellurium of high purity. Methods for the determination of selenium (with Change No. 1)

GOST 19709.2−83

Group B59

STATE STANDARD OF THE USSR

TELLURIUM OF HIGH PURITY

Methods for determination of selenium

Tellurium of high purity. Methods for determination of selenium*

______________

* The name of the standard. Changed the wording, Rev. N 1.

AXTU 1709

Valid from 01.01.85
to 01.01.90*
_______________________________
* Expiration removed
Protocol N 4−93 inter-state Council
for standardization, Metrology and certification
(IUS N 4, 1994). — Note the manufacturer’s database.

DEVELOPED by the Ministry of nonferrous metallurgy of the USSR

PERFORMERS

V. P. Savraev, L. I. Zelensky, M. G. Sun, E. V. Lisitsyna, L. I. Maxi, E. V. Borovikova, N. Ryabova

INTRODUCED by the Ministry of nonferrous metallurgy of the USSR

Member Of The Board Of A. P. Snurnikov

APPROVED AND put INTO EFFECT by Decision of the USSR State Committee on standards of 26 September 1983 N 4535

REPLACE GOST 19709.2−74

The Change N 1, approved and put into effect by the Decree of the USSR State Committee for standards from 20.02.89 N 269 from 01.09.89

Change No. 1 made by the manufacturer of the database in the text IUS N 5, 1989


This standard specifies the extraction-fluorometric (at a mass fraction of selenium from to 0,000005 0,0005%) and spectrophotometric (for the mass concentration of selenium is from 0.0001 to 0.02%) methods for determination of selenium in tellurium of high purity.

A spectrophotometric method based on the formation of compounds of selenium with o-phenylendiamine at pH 1−2, absorbing light in the ultraviolet region of the spectrum at a wavelength of 335 nm. The resulting compound is extracted with benzene. Tellurium is associated with citric acid.

(Changed edition, Rev. N 1).

1. GENERAL REQUIREMENTS

1.1. General requirements for method of analysis according to GOST 22306−77 with the Supplement.

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

1.1.2. Control of the correctness of the results of the analysis carried out by the method of standard addition.

Mass fraction of selenium in a Supplement (a standard solution) must be 80−120% of its content in the analyzed material.

The amount of additives is determined by difference , where and  — the results of the analysis of the sample and the sample with the additive , calculated as the arithmetic mean of two parallel definitions, the differences between them should not exceed the permissible values given in the standard.

The result of the analysis is considered correct if the value found additives different from the calculated values by no more than where and  — the permissible discrepancy between the results of parallel measurements of selenium in the sample and in the sample with dobavka

th .

1.1.1, 1.1.2. (Changed edition, Rev. N 1).

2. SAFETY REQUIREMENTS

2.1. Safety requirements — according to GOST 19709.1−83.

3. APPARATUS, MATERIALS AND REAGENTS

A spectrophotometer of any type for measuring light absorption in the ultraviolet region of the spectrum.

Hydrochloric acid by the GOST 3118−77.

Nitric acid GOST 4461−77.

Citric acid according to GOST 3652−69, a solution with a mass fraction of 50%.

Formic acid according to GOST 5848−73.

Ammonia water according to GOST 3760−79.

Salt is the disodium Ethylenediamine — N, N, N', N'-tetraoxane acid (Trilon B) according to GOST 10652−73, 0.1 M solution.

on-Phenylendiamin hydrochloric acid solution with a mass fraction of 1%, freshly prepared (the reagent should be light).

Benzene according to GOST 5955−75 or toluene according to GOST 5789−78.

Universal indicator paper.

Selenium GOST 5455−74.

Distilled water GOST 6709−72.

(Changed edition, Rev. N 1).

4. PREPARATION FOR ASSAY

4.1. Preparation of standard solutions of selenium

Solution a: 50.0 mg of selenium dissolved in 10 cmof hydrochloric acid with the addition of 5−7 drops of nitric acid by heating on a water bath, add 20 cmof water.

The cooled solution is poured into a measuring flask with a capacity of 500 cm, add 15 cmof hydrochloric acid and was adjusted to the mark with water.

1 cmof solution A contains 0.1 mg of selenium.

Solution B: 5 cmmortar And transferred to a volumetric flask with a capacity of 250 cm, add 5 cmof hydrochloric acid and was adjusted to the mark with water.

1 cmof a solution contains 0.002 mg of selenium.

5. ANALYSIS

5.1. A portion of the tellurium mass of 1,000 g was placed in a conical flask with a capacity of 100 cm, 15 cm addsalt and 2 cmof nitric acid. The beaker cover watch glass and heated in a water bath to dissolve the tellurium. Watch glass is removed and the solution is evaporated to a volume of 5 cm. For the mass concentration of selenium more than 0.001% solution was placed in a volumetric flask with a capacity of 100 cm, adjusted to the mark with water and taken aliquot part containing 2−16 mcg of selenium.

The cooled solution or it aliquotes part add 25 cmof water, 12 cmof the citric acid solution, 3 cmof the solution Trilon B, and 1 cmof formic acid. Set the pH of the solution is equal to 1−2 on the universal indicator paper by adding a drop of ammonia. Pour 1 cmof solution on-Phenylenediamine and leave for 20 min.

The solution is poured into a separating funnel with a capacity of 150 cm, add 25 cmof benzene (toluene) and extracted 2 minutes After separation of the liquids, the organic layer decanted into a dry test tube and measure the optical density on the spectrophotometer at a wavelength of 335 nm in a cuvette with the thickness of the light absorbing layer was 50 mm.

Solution comparison is the solution of the reference experiment.

The content of selenium set by the calibration schedule.

(Changed edition, Rev.

N 1).

5.2. To build a calibration curve in a conical flask with a capacity of 100 cmplaced 0; 0,5; 1,0; 2,0; 4,0; 6,0 and 8.0 cmof a standard solution B, which corresponds to 0; 1; 2; 4; 8; 12 and 16 mcg of selenium. In each flask pour the water up to 30−35 cm, 8 cmof a solution of citric acid and then do as specified in clause 5.1.

According to the obtained values of optical density of solutions and the corresponding content of selenium build the calibration graph.

6. PROCESSING OF THE RESULTS

6.1. Mass fraction of selenium () in percent is calculated by the formula

,

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

 — weight of tellurium,

6.2. The difference between the two results of parallel measurements and the difference of two analysis results with a confidence probability of 0.95 does not exceed values of allowable differences specified in table.1.

Table 1

6.1, 6.2. (Changed edition, Rev. N 1).

7. EXTRACTION-FLUORIMETRIC METHOD FOR THE DETERMINATION OF SELENIUM

7.1. The essence of the method

The method is based on the formation of compounds of selenium with 2,3-diaminonaphthalene, extracting it with n-hexane and measuring the intensity of luminescence of the extract.

7.2. Apparatus, materials and reagents

The spectrofluorimeter M-850 or similar.

Universal indicator paper.

The agate mortar.

Nitric acid according to GOST 11125−84.

Sulfuric acid according to GOST 14262−78.

Hydrochloric acid according to GOST 14261−77, solution 0,1 mol/DM.

Formic acid according to GOST 5848−73.

Ammonia water according to GOST 24147−80.

n-Hexane.

Ethyl alcohol GOST 18300−87.

Salt is the disodium Ethylenediamine — N, N, N', N' — tetraoxane acid (Trilon B) according to GOST 10652−73, solution 0,025 mol/DM.

2,3-diaminonaphtalene a solution of 5 g/DM; a portion of the reagent a mass of 0.5 g is dissolved in 100 cmof solution of hydrochloric acid, the solution transferred to a separatory funnel with a capacity of 150 cmand extracted impurities 30 cmn-hexane 1 min. the Aqueous phase is poured into a dark bottle with a glass stopper; the solution is ready for use within 3 days.

Selenium of high purity.

The standard solutions of selenium.

Solution a: a portion of the selenium mass 0,1000 g is placed in a conical flask with a capacity of 100 cmand dissolved by heating in a water bath 10 cm ina mixture of nitric and hydrochloric acids (3:1), evaporated to wet salts, add 5 cmof sulphuric acid and heated until the appearance of sulphuric acid fumes. The solution was cooled and transferred to volumetric flask with a capacity of 100 cm, adjusted to the mark with water and mix.

1 cmof the solution contains 1 mg selenium.

Solution B: 5 cmsolution And placed in a volumetric flask with a capacity of 500 cm, was adjusted to the mark with hydrochloric acid and stirred.

1 cmof a solution contains 0.01 mg of selenium.

Solution: 5 cmof solution B is placed in a volumetric flask with a capacity of 500 cm, was adjusted to the mark with hydrochloric acid and stirred.

1 cmof the solution contains 0,0001

mg of selenium.

7.3. Analysis

The analyzed sample is placed in an agate mortar and ground by adding at the end 10 cmof ethanol; the sample is then dried.

A portion of the tellurium mass 1,0000 g when the mass fraction of selenium from 5·10to 5·10% or 0,1000 g when the mass fraction of selenium from 5·10to 5·10% was placed in a beaker with a capacity of 50 cmand poured into conformity with its linkage 3 or 1.5 cmof hydrochloric acid and 1 or 0.5 cmof nitric acid. The beaker covered with a funnel and heated until complete dissolution of the sample, and then boiled to remove oxides of nitrogen. The solution was cooled and added to 2 cmof the solution Trilon B, 20 cmof water and set the pH of the solution is 2 by universal indicator paper, adding dropwise ammonia (about 2 cm). Solution white amorphous precipitate tellurite acid heated to boiling and kept on the hot plate to the transition of an amorphous precipitate in a crystalline (5−10 min) and then cooled.

The solution was filtered through filter «blue ribbon» in a volumetric flask with a capacity of 50 cm, which pre-pour 2 cmof hydrochloric and 1 cmof formic acid. The solution was stirred and after 30 min add 2cmof a solution of 2,3-diaminonaphthalene for the mass concentration of selenium is less than 1·10% or 4 cmof a solution of 2,3-diaminonaphthalene for the mass concentration of selenium more than 1·10%. The contents of the flask brought to the mark with water and mix. After 1 h the solution was transferred to a separatory funnel with a capacity of 100 cm, add 5 cmn-hexane and extracted for 1 min. After separation of the layers the organic phase is decanted into a dry test tube with a glass stopper.

The content of selenium find by the method of additions. This is carried out in parallel determination of selenium in two batches of samples with additives of selenium standard solution B, or V. the mass of selenium in add solution B or C are selected in such a way that being related to the weight of the portion, it was from 1.2to 0.8selenium in the sample. The second Supplement should be twice the first. Additive solutions and administered in a volumetric flask with a capacity of 50 cmprior to filtering the solution to precipitate.

Through all stages of the analysis carried out two test experience on reagents.

The luminescence spectra of the complex recorded consecutively in the region of 500−580 nm, since more additives. The band maximum is 519 nm. The excitation wave length corresponds to 373 nm. The sensitivity of the amplifier, the input and output slit is adjusted depending on

the magnitude of the signal.

7.4. Processing of the results

7.4.1. Mass fraction of selenium () in percent is calculated by the formula

,

where is the mass of added selenium, mg;

 — the height of the peak for the sample solution, mm;

 — the height of the peak for a solution in the reference experiment, mm.

 — the height of the peak for the sample solution with the addition of, mm.

 — weight of tellurium,

7.4.2. The difference between the two results of parallel measurements and the difference of two analysis results with a confidence probability of 0.95 does not exceed values of allowable differences specified in table.2.

Table 2

Section 7. (Added, Rev. N 1).