GOST 13938.11-78

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  ГОСТ 13938.11-78

GOST 13938.11−78 Copper. Method for the determination of arsenic (with Amendments No. 1, 2, 3)

GOST 13938.11−78

Group B59

INTERSTATE STANDARD

COPPER

Method for the determination of arsenic

Copper. Method for determination of arsenic

AXTU 1709

Date of introduction 1979−01−01

INFORMATION DATA

1. DEVELOPED AND INTRODUCED by the Ministry of nonferrous metallurgy of the USSR

DEVELOPERS

G. P. Giganov, E. M. Peneva, A. A. Blyahman, E. D. Shuvalov, A. N. Savelieva

2. APPROVED AND promulgated by the Decree of the State Committee of standards of Ministerial Council of the USSR from 24.01.78 N 155

3. REPLACE GOST 13938.11−68

4. The standard corresponds to the international standard ISO 3220−75

5. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

6. Limitation of actions taken by Protocol No. 3−93 Interstate Council for standardization, Metrology and certification (ICS 5−6-93)

7. REPRINT (November 1999) with Amendments No. 1, 2, 3, approved in may 1982, June 1985, April 1988 (IUS 8−82, 8−85, 7−88)


This standard sets the photometric method for the determination of arsenic in copper grades according to GOST 859* (mass fraction of arsenic from 0.0005 to 0.1%).
______________
* On the territory of the Russian Federation GOST 859−2001. — Note the manufacturer’s database.

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 600−680 nm or 820.

(Changed edition, Rev. N 3).

1. GENERAL REQUIREMENTS

General requirements for methods of analysis and safety requirements when performing tests according to GOST 13938.1.

Sec. 1. (Changed edition, Rev. N 3).

2. APPARATUS, REAGENTS AND SOLUTIONS

Apparatus for distillation of arsenic trichloride (see drawing).

Apparatus for distillation of arsenic trichloride

1 — flask for distillation; 2 — dropping funnel; 3 — nozzle Kjeldahl;
4 — refrigerator; 5 — receiver; 6 — a tube with extension; 7 — control receiver

Drying oven with thermostat.

Photoelectrocolorimeter or spectrophotometer with all accessories.

Nitric acid according to GOST 4461 and diluted 1:1.

Hydrochloric acid according to GOST 14261 or GOST 3118, containing no arsenic, and diluted 1:1.

Ammonium molybdate according to GOST 3765, a solution of 10 g/DM; 10 g of ammonium molybdate dissolved in 500 cm2 mol/DMsolution of sulphuric acid. The solution was filtered and poured acid to 1 DM.

Sulfuric acid according to GOST 4204, diluted 1:1 and 2 mol/DMsolution.

Hydrogen peroxide (perhydrol) according to GOST 10929.

Hydrazine sulfate according to GOST 5841, a solution of 10 g/DM.

Sodium hydroxide according to GOST 4328, solution 100 g/DM.

Potassium bromide according to GOST 4160.

Reaction mixture: 10 cmsolution of ammonium molybdate is transferred to a volumetric flask with a capacity of 100 cm, add 1 cmof solution of hydrazine sulphate, made up to the mark with water and mix thoroughly.

The mixture is prepared immediately before use.

Arsenious anhydride according to GOST 1973.

The standard solutions of arsenic.

Solution A, prepared as follows: 0,132 g of arsenious anhydride were placed in a glass with a capacity of 100 cm, flow 10 cmof a solution of hydrate of sodium oxide. The solution is poured into a measuring flask with a capacity of 1 DM, made up to the mark with water and mix.

1 cmof solution A contains 0.1 mg of arsenic.

Solution B is prepared as follows: 50 cmsolution And transferred to a volumetric flask with a capacity of 250 cm, and topped to the mark with water.

1 cmof the solution contains 0.02 mg of arsenic.

(Changed edition, Rev. N 1, 3).

3. ANALYSIS

3.1. A sample of copper is placed in a beaker with a capacity of 250 cmand add nitric acid diluted 1:1. The weight of copper and the amount of acid indicated in the table.1.

Table 1

The contents of the Cup was heated until complete dissolution of the sample, and when heated removes the bulk of acid. 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 contents of the beaker cool, add 10−15 cmof water and again heated to release vapors of sulfuric acid.

To the residue add 50 cmof water and the solution transferred into a distillation flask. Add 5 g of hydrazine sulfate, 1 g of potassium bromide and close the flask tube, equipped with a drip funnel and a Kjeldahl nozzle.

In the receiver pour 100 cmwater and 1 cmof hydrogen peroxide and connect all parts of the device. 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 determining the mass fraction of arsenic from 0.0005 to 0.002% distillate used for determination of the mass fraction of arsenic from 0.002 to 0.1% use aliquot part of the distillate (see table.1).

Solutions from the receivers poured into a glass with a capacity of 250 cm, add 10 cmof nitric acid and gently evaporated until dry at 120−130 °C. To remove the remainder of the nitric acid beaker put into an oven and left for 1 h at 135−140 °C. the Residue was cooled and moistened with 2 drops of sodium hydroxide solution. 10−12 min. to the residue add 40 cmof the reaction mixture, heated and boiled for 3−5 min. the Solution was cooled, poured into a volumetric flask with a capacity of 50 cm, made up of the reaction mixture up to the mark and mix.

20 min after the formation of the complex michalopolous measure the optical density of the solution at wavelengths of 820 or 600−680 nm in a cuvette with an optimum thickness of the layer. Solution for comparison in the measurement of optical density is water. At the same time carried out two test experience with all the applied reagents. The average value of optical density in the reference experiment is subtracted from the optical density of the analyzed solution.

The mass of arsenic set by the calibration schedule, constructed as described in section 3.2.

(Changed edition, Rev. N

1).

3.2. Construction of calibration curve

In glasses with a capacity of 100 cmplaced: 0; 0,5; 1,0; 2,0 and 4,0 cmstandard solution B, which corresponds to 0; 10; 20; 40 and 80 µg of arsenic, pour 5 cmof nitric acid, cautiously evaporate the solution and then carry out the analysis as described in section 3.1.

Solution comparison in the measurement of the optical density of solutions is a solution, which was not introduced a standard solution of arsenic.

On the found values of optical density and corresponding concentration of arsenic build the calibration graph.

4. PROCESSING OF THE RESULTS

4.1. Mass fraction of arsenic , in percent calculated by the formulas

or

,

where is the mass of the copper sample, g;

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

 — the volume of the analyzed solution, cm;

 — volume aliquote part of the analyzed solution, cm.

(Changed edition, Rev. N 1).

4.2. Discrepancies in the results of two parallel measurements and the two tests should not exceed the values given in table.2.

Table 2

(Changed edition, Rev. N 3).

4.3. Allowed determination of arsenic by other methods.

(Added, Rev. N 3).