GOST 20996.10-82

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  ГОСТ 20996.10-82

GOST 20996.10−82 Selenium technical. Methods for determination of tellurium (with Amendments No. 1, 2)

GOST 20996.10−82*

Group B59

INTERSTATE STANDARD

SELENIUM TECHNICAL

Methods for determination of tellurium

Selenium. Methods of tellurium determination

AXTU 1709

Date of introduction 1983−07−01

Resolution of the USSR State Committee on standards of 22 June 1982, N 2481 date of introduction is established with 01.07.83

Limitation of actions taken by Protocol No. 7−95 Interstate Council for standardization, Metrology and certification (ICS 11−95)

REPLACE GOST 10431−63 in part of sec. VII

* PUBLISHING (July 2000) with amendment No. 1 approved in December 1987 (IUS 3−88)

The Change N 2, approved and promulgated by the Order of Rosstandart on 09.04.2015 N 251-St c 01.09.2015

Change No. 2 made by the manufacturer of the database in the text ICS N 7, 2015

This standard sets the photometric method for the determination of tellurium (if the mass fraction of tellurium from 0.03% to 0.6%).

(Changed edition, Rev. N 1, 2).

1A. NORMATIVE REFERENCES

This standard uses the regulatory references to the following international standards:

GOST 1770−74 (1042−83 ISO, ISO 4788−80) Glassware volumetric laboratory glass. Cylinders, beakers, flasks, test tubes. General specifications

GOST 3118−77 Reagents. Hydrochloric acid. Specifications

GOST 3760−79 Reagents. The aqueous ammonia. Specifications

GOST 4204−77 Reagents. Sulphuric acid. Specifications

GOST 4461−77 Reagents. Nitric acid. Specifications

GOST 6709−72 distilled Water. Specifications

GOST 8864−71 Reagents. Sodium N, N-diethyldithiocarbamate 3-water. Specifications

GOST 10652−73 Reagents. Salt is the disodium Ethylenediamine-N, N, N', N'-tetraoxane acid 2-water (Trilon B). Specifications

GOST 20288−74 Reagents. The carbon tetrachloride. Specifications

GOST 20996.0−82 Selenium technical. General requirements for methods of analysis

GOST 24104−2001* laboratory Scales. General technical requirements
_______________
* On the territory of the Russian Federation GOST R 53228−2008 «Scales non-automatic actions. Part 1. Metrological and technical requirements. Test».


GOST 25336−82 Glassware and equipment laboratory glass. The types, basic parameters and dimensions

GOST ISO 5725−6-2002* Accuracy (trueness and precision) of methods and measurement results. Part 6. The use of precision values in practice.
________________
* On the territory of the Russian Federation GOST R ISO 5725−6-2002 «Accuracy (trueness and precision) of methods and measurement results. Part 6. The use of precision values in practice».


Note — When using this standard appropriate to test the effect of reference standards in the information system of General use — on the official website of the Federal Agency for technical regulation and Metrology on the Internet or published annually by the information sign «National standards» published as on January 1 of the current year and related information published monthly indexes published in the current year. If the reference standard is replaced (changed), when using this standard should be guided by replacing (amended) standard. If the reference standard is cancelled without replacement, then the situation in which the given link applies to the extent that does not affect this link.

(Added, Rev. N 2).

1B. CHARACTERISTICS OF INDICATORS OF MEASUREMENT ACCURACY

A measure of the accuracy of measuring the mass fraction of tellurium corresponds to the characteristics given in table 1 (with R=0,95).

Limit values of repeatability and reproducibility of measurements for a confidence probability P=0.95 is given in table 1.


Table 1 — values of the indicator of measurement accuracy, limits of repeatability and reproducibility of measurements of mass fraction of tellurium

Percentage

(Added, Rev. N 2).

1. GENERAL REQUIREMENTS

1.1. General requirements for methods of analysis GOST 20996.0−82.

2. MEASUREMENT MEANS, AUXILIARY DEVICES, MATERIALS AND SOLUTIONS

When performing measurements using the following measuring instruments and auxiliary devices:

— spectrophotometer or photoelectrocolorimeter with all accessories necessary for measurements at a wavelength of 410−420 nm;

— special laboratory scales of accuracy class according to GOST 24104;

— the stove is electric with a closed heating element for temperature up to 400 °C;

— volumetric flasks 2−100−2 according GOST 1770;

— glasses-1−100 TCS-1−250 TCS according to GOST 25336;

— separating funnel VD-1−250 TC GOST 25336;

— hour glass.

When taking measurements, use the following products and solutions:

— distilled water according to GOST 6709;

— nitric acid according to GOST 4461;

— hydrochloric acid according to GOST 3118;

— sulfuric acid according to GOST 4204, diluted 1:1;

— sodium N, N-diethyldithiocarbamate according to GOST 8864, solution mass concentration 10 g/DM;

— carbon tetrachloride according to GOST 20288;

— ammonia water according to GOST 3760;

— salt is the disodium Ethylenediamine-N, N, N', N'-tetraoxane acid, 2-water (Trilon B) according to GOST 10652, solution mass concentration 10 g/DM;

— methylcrotonyl purple, indicator 1 g/lin alcohol;

— tellurium [1], [2]

(Changed edition, Rev. N 1, 2).

3A. PREPARATIONS FOR THE MEASUREMENTS

3A.1. To construct the calibration curve, prepare solutions of known concentration of tellurium
In preparing the solution And the mass concentration of tellurium in 1 mg/cma portion of the tellurium mass of 0.1 were placed in a glass with a capacity of 100 cm, pour from 8 to 10 cmof hydrochloric acid, add 5 to 8 drops of nitric acid and heated to dissolve sample. Cooled, placed in a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

In the preparation of a solution of mass concentration of tellurium 0.1 mg/cma 10 cm aliquotof solution A is placed in a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

3A.2. construction of calibration curve

Six separatory funnels with a capacity of 200 cmeach are placed 0; 0,1; 0,2; 0,5; 1,0; 1,5 cm()solution B, which corresponds to 0; 0,01; 0,02; 0,05; 0,1; 0,15 mg of tellurium, topped up with water to 20 cm. To the solution was added 2−3 drops of indicator and neutralized with ammonia to slightly alkaline reaction (to purple color). Pour 1 cmof a solution of sodium diethyldithiocarbamate and continue as specified in 3.3.1. According to the obtained results build a calibration curve.

A solution of comparison, using the blank solution experience.

Section 3A (Introduced later, Rev. N 2).

3. PHOTOCOLORIMETRIC METHOD FOR THE DETERMINATION OF TELLURIUM

3.1. The essence of the method

The method is based on reaction of formation of colored complex compounds of ions of tellurium with sodium diethyldithiocarbamate and subsequent measurement of optical density at a wavelength of 410−420 nm.

3.2. (Deleted, Rev. N 2).

3.3. Analysis

3.3.1. A portion of the selenium mass 0.5 or 1 g is placed in a beaker with a capacity of 200−300 cm, pour 15−20 cmof nitric acid, cover with watch glass (glass plate) and allowed to stand without heating until the termination of the rapid allocation of nitrogen oxides. Glass (plate) is removed, washed with water on the glass and evaporate the solution to the wet state. Evaporation with 5−7 cmof nitric acid is repeated twice, each time evaporating to dryness.

Go to the dry residue of 5−7 cmof sulfuric acid solution (1:1) and evaporated to release thick vapors of sulfuric acid. Cool, wash the side of the Cup with water and again evaporated to release vapors of sulfuric acid. Add 30−40 cmof water, heated to boiling and boil to dissolve the salts. After cooling, the resulting solution was transferred to a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

Select aliquot part 5−20 cm(depending on the mass fraction of tellurium) and transferred to a separatory funnel with a capacity of 150−200 cm. To the solution was added 2−3 drops of indicator and neutralized with ammonia to purple color. Pour 1 cm ofTrilon B and again ammonia until the appearance of the violet color of the solution.

To the neutralized solution was added to 1 cmof a solution of sodium diethyldithiocarbamate, 20−30 cmof carbon tetrachloride and perform the extraction for 1 min.

After separation the organic phase is placed in a cuvette with the thickness of the absorbing layer is 20 mm and the optical density is measured on photoelectrocolorimeter, using a filter with maximum transmittance at a wavelength of 415 nm. As a solution comparison solution is used in the reference experiment.

Mass of tellurium find for the calibration schedule.

(Changed edition, Rev. N 1).

3.3.2. (Deleted, Rev. N 2).

3.4. Processing of the results

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

,

where  — the amount of tellurium found in the calibration graphics mg;

 — volume of the volumetric flask, cm;

 — volume aliquote part of the solution, cm;

 — weight of selenium,

3.4.2. The measurement results take the arithmetic mean of two parallel definitions, provided that the absolute difference between them in terms of repeatability does not exceed the value (at confidence probability P=0,95) repeatability limit rgiven in table 1.

If the difference between the highest and lowest results of parallel measurements exceeds the limit value of the frequency of occurrence, perform the procedure described in GOST ISO 5725−6 (paragraph 5.2.2.1)

(Changed edition, Rev. N 1, 2).

3.4.3. The absolute value allowable discrepancies between the two measurement results obtained in different laboratories, should not exceed the limit values for the reproducibility given in table 1 (at confidence probability P=0,95). At default of this condition can be used the procedure set out in GOST ISO 5725−6.

(Added, Rev. N 1); (Revised edition, Edit. N 2).

Bibliography

Bibliography (added, Rev. N 2).