GOST 13938.11-2014

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  ГОСТ 13938.11-2014

GOST 13938.11−2014 Copper. The method of determining the mass fraction of arsenic

GOST 13938.11−2014

Group B59

INTERSTATE STANDARD

COPPER

The method of determining the mass fraction of arsenic

Copper. Method for determination of arsenic mass fraction

ISS 77.120.30

Date of introduction 2016−01−01

Preface

Goals, basic principles and main procedure of works on interstate standardization established in GOST 1.0−92 «interstate standardization system. Basic provisions» and GOST 1.2−2009 «interstate standardization system. Interstate standards, rules and recommendations on interstate standardization. Rules of development, adoption, application, renewal and cancellation"

Data on standard

1 DEVELOPED by the Open joint-stock company «Scientific-research and design Institute of enrichment and mechanical processing of minerals «URALMEKHANOBR» (JSC «uralmekhanobr»), Technical Committee for standardization TC 368 «Copper"

2 as AMENDED by the Federal Agency for technical regulation and Metrology (Rosstandart)

3 ACCEPTED by the Interstate Council for standardization, Metrology and certification (Protocol of November 14, 2014 N 72-N)

The adoption voted:

4 by Order of the Federal Agency for technical regulation and Metrology of April 2, 2015 N 207-St inter-state standard GOST 13938.11−2014 introduced as the national standard of the Russian Federation from 1 January 2016.

5 REPLACE GOST 13938.11−78


Information about the changes to this standard is published in the annual reference index «National standards», and the text changes and amendments — in monthly information index «National standards». In case of revision (replacement) or cancellation of this standard a notification will be published in the monthly information index «National standards». Relevant information, notification and lyrics are also posted in the information system of General use — on the official website of the Federal Agency for technical regulation and Metrology on the Internet

1 Scope

This standard specifies a photometric method for measuring the mass fraction of arsenic in copper (in the range from 0.0005% to 0.100%).

2 Normative references

The present standard features references to the following international standards:

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

GOST 1973−77 arsenious Anhydride. Specifications

GOST 3118−77 Reagents. Hydrochloric acid. Specifications

GOST 3765−78 Reagents. Ammonium molybdate. Specifications

GOST 4160−74 Reagents. Potassium bromide. Specifications

GOST 4204−77 Reagents. Sulphuric acid. Specifications

GOST 4328−77 Reagents. Sodium hydroxide. Specifications

GOST 4461−75* Reagents. Nitric acid. Specifications
________________
* Probably, the error of the original. Should read: GOST 4461−77. — Note the manufacturer’s database.


GOST 5841−74 Reagents. Hydrazine sulfate

GOST 6709−72 distilled Water. Specifications

GOST 10929−76 Reagents. Hydrogen peroxide. Specifications

GOST 14261−77 hydrochloric Acid of high purity. Specifications

GOST 24104−2001laboratory 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 25086−2011 non-ferrous metals and their alloys. General requirements for methods of analysis

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

GOST 29169−91 (ISO 648−77) oils. Pipette with one mark

GOST 29227−91 (ISO 835−1-81) oils. Pipettes are graduated. Part 1. General requirements

GOST 31382−2009 Copper. Methods of analysis

GOST ISO 5725−6-2003Accuracy (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.


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 in the annual information index «National standards» published as on January 1 of the current year, and the editions of the monthly information index «National standards» for 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.

3 General provisions

General requirements for the method of measurement according to GOST and GOST 25086 31382.

4 Characteristics of indicators of measurement accuracy

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

Limit values of repeatability and reproducibility of the measurement at a confidence probability P = 0.95 is given in table 1.


Table 1 — Values of the measure of the accuracy, limits of repeatability and reproducibility of measurements of mass fraction of arsenic at confidence probability P=0,95

Percentage

5 measurement Means, auxiliary devices, materials, solutions

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

installation for the distillation of arsenic trichloride according to figure 1;

— spectrophotometer or photoelectrocolorimeter, providing measurements at the wavelengths of 820 nm or from 600 to 680 nm;

— laboratory drying oven with thermostatic control, ensuring the heating temperature up to 250 °C;

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

— volumetric flasks 2−50−2, 2−100−2, 2−250−2, 2−1000−2 according GOST 1770;

— glasses-1−100 TCS-1−250 TCS-1−1000 TCS according to GOST 25336;

slab heating [1]* ensuring the heating temperature up to 400 °C or equivalent;
________________
* POS. [1]-[2], see Bibliography. — Note the manufacturer’s database.

pipettes not lower than 2nd accuracy class according to GOST and GOST 29169 29227;

glass hour;

— funnel In-36−80 TC GOST 25336.

When taking measurements, use the following products and solutions:

— ammonium molybdate according to GOST 3765, solution mass concentration of 10 g/lin sulfuric acid molar concentration of 2 mol/DM(store in a plastic container);

— hydrazine sulfate according to GOST 5841, solution mass concentration 10 g/DM;

— distilled water according to GOST 6709;

— nitric acid according to GOST 4461 and diluted 1:1;

Figure 1 — Installation for the distillation of arsenic

1 — boiling flask; 2 — dropping funnel; 3 — nozzle with droplet separator; 4 — fridge 5 — the first receiver; 6 — breather pipe with the ball; 7 — control the receiver with the water for gas recovery

Figure 1 — Installation for the distillation of arsenic

recovery mixture;

— arsenious anhydride according to GOST 1973;

— solution of arsenic of known concentration;

— sodium hydroxide (sodium hydroxide) according to GOST 4328, solution mass concentration of 100 g/DM;

— sulfuric acid according to GOST 4204, diluted 1:1 and the solution molar concentration of 2 mol/DM;

— potassium bromide according to GOST 4160;

acid salt of high purity according to GOST 14261, or hydrochloric acid according to GOST 3118 containing no arsenic;

— hydrogen peroxide according to GOST 10929;

filters obestochennye [2] or similar.

Notes

1 allowed the use of other measuring instruments of the approved type, auxiliary devices and materials, technical and metrological characteristics are not inferior to mentioned above.

2 allowed the use of reagents produced by other normative documents, provided that their metrological characteristics of measurement results, given in this standard.

6 the essence of the method

The method is based on the reaction of formation of arsenic-molybdenum complex is colored blue. Previously separate arsenic from copper and interfering impurities by distillation of trichloride arsenic from hydrochloric acid solution. Optical density of the solution is measured at a wavelength of 820 nm or from 600 to 680 nm.

7 Preparing for measurement

7.1 For preparation of a solution of ammonium molybdate mass concentration of 10 g/DM: a sample of ammonium molybdate weighing 10 g was placed in a beaker with a capacity of 1000 cmand 500 cm pour thesulfuric acid molar concentration of 2 mol/DM. The solution was filtered, transferred to a measuring flask with volume capacity of 1000 cm, and then filled to the mark with sulfuric acid, the molar concentration of 2 mol/land stirred.

7.2 Preparation of restorative mixtures

For the preparation of a restorative blend of 10 cmsolution of ammonium molybdate mass concentration of 10 g/DMis placed in a volumetric flask with a capacity of 100 cm, add 1 cmof a solution of hydrazine sulfate mass concentration 10 g/DM, made up to the mark with water and mix thoroughly.

7.3 To build a calibration curve, prepare solutions of known arsenic concentrations.

In preparing the solution And the mass concentration of arsenic of 1 mg/cma portion of the arsenious anhydride weight 0,1320 g were placed in a glass with a capacity of 100 cm, and dissolve in low heat 10 cmof sodium hydroxide solution, the mass concentration of 100 g/DM. The solution is poured into a measuring flask with volume capacity of 1000 cm, dilute with water to 300 cm, cooled and topped to the mark with water and mix.

In the preparation of a solution with a mass concentration of arsenic 0.02 mg/cm5 cmsolution And placed in a volumetric flask with a capacity of 250 cm, made up to the mark with water and mix.

7.4 Construction of calibration curve

In five glasses with a capacity of 100 cmis placed 0; 0,5; 1,0; 2,0 and 4,0 cmof solution B, which corresponds to 0; 10; 20; 40 and 80 µg of arsenic. In each glass pour 5 cmof nitric acid, cautiously evaporate the solutions to dryness at a temperature of from 120 °C to 130 °C. To completely remove the residue of nitric acid beakers were put into an oven and left for 1 h at a temperature of from 135 °C to 140 °C.

The residue was cooled, moistened with two drops of sodium hydroxide solution mass concentration of 100 g/DM. Using the time interval from 10 to 12 min. add 40 cmof restorative mixture is heated and boiled for 3−5 minutes. The solution was cooled, transferred to a volumetric flask with a capacity of 50 cm, made up of the reducing mixture to the mark and mix.

After 20 minutes, measure the optical density of the solution at a wavelength of 820 nm or from 600 to 680 nm in a cuvette with an optimum thickness of the light absorbing layer.

A solution of comparison used water. Build a graph taking into account the idle experience (reference solution with zero concentration of arsenic).

8 performance measurement

A sample of copper is placed in a beaker with a capacity of 250 cm, and pour nitric acid, diluted 1:1. The weight of the portion of copper (depending on the mass fraction of arsenic) and the volume of acid given in table 2.


Table 2

Beaker cover watch glass and heated until complete dissolution of the sample and prior to the removal of nitrogen oxides, remove the glass. The solution was poured 25 cmof sulphuric acid diluted 1:1, is heated to release vapors of sulfuric acid and heating was continued for another 10 min.

The glass is cooled, poured 10 to 15 cmof water and again heated to release vapors of sulfuric acid.

To the residue poured in 50 cmof water and transfer the solution into a flask for distillation. Add 5 g of hydrazine sulfate, 1 g of potassium bromide and close the flask with a stopper, equipped with a nozzle with droplet separator and drip funnel.

In the receiver pour 100 cmwater and 1 cmof hydrogen peroxide and connect all parts of the installation. The control receiver is placed a volume of water to the level it was at 1−2 mm above the end of the tube.

In the distillation flask containing the solution, is introduced through the drip funnel 100 cmof hydrochloric acid, heat the solution to boiling and distilled 2/3 of the volume of the liquid.

When measuring the mass fraction of arsenic in the range from 0.0005% to 0.002% of the distillate is used for measuring the mass fraction of arsenic in the range from 0.002% to 0.1% using aliquots of the distillate, the values of which are given in table 2.

Solutions from the receivers poured into a glass with a capacity of 250 cm, flow 10 cmof nitric acid and gently evaporated solutions to dryness at a temperature of from 120 °C to 130 °C. To completely remove the residue of nitric acid beakers were put into an oven and left for 1 h at a temperature of from 135 °C to 140 °C.

The residue was cooled, moistened with two drops of sodium hydroxide solution mass concentration of 100 g/DM. Using the time interval from 10 to 12 min. add 40 cmof restorative mixture is heated and boiled for 3−5 minutes. The solution was cooled, transferred to a volumetric flask with a capacity of 50 cm, made up of the reducing mixture to the mark and mix.

After 20 minutes, measure the optical density of the solution at a wavelength of 820 nm or from 600 to 680 nm in a cuvette with an optimum thickness of the light absorbing layer.

A solution of comparison used water. At the same time carried out two blanks of the experience with all used reagents. The average value of the optical density of the blank experience is subtracted from the optical density of the analyzed solution.

The mass of arsenic set by the calibration schedule, constructed as specified in 7.4.

9 Processing of measurement results

9.1 Mass fraction of arsenic X, %, is calculated by the formula

, (1)

or

, (2)

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

m — mass of sample of copper, g;

V — volume of the analyzed solution, cm;

V — volume of the aliquot of the analyzed solution, cm.

9.2 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).

9.3 Differences between measurements obtained in two laboratories, should not exceed the limit values for the reproducibility given in table 1. In this case, the final result can be accepted their mean value. At default of this condition can be used the procedure set out in GOST ISO 5725−6.

Bibliography