GOST 25284.4-95

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  ГОСТ 25284.4-95

GOST 25284.4−95 Alloy zinc. Methods for determination of lead

GOST 25284.4−95

Group B59

INTERSTATE STANDARD

ZINC ALLOYS

Methods for determination of lead

Zinc alloys. Methods for determination of lead

ISS 71.040.40*
AXTU 1709
____________________
* In the index «National standards», 2008
ISS 77.120.60. — Note the manufacturer’s database.

Date of introduction 1998−01−01

Preface

1 DEVELOPED by the Donetsk state Institute of non-ferrous metals (Danism); International technical Committee MTC 107

SUBMITTED to the State Committee of Ukraine for standardization, Metrology and certification

2 ADOPTED by the Interstate Council for standardization, Metrology and certification (EASC Protocol No. 7 of April 26, 1995)

The adoption voted:

3 Resolution of the State Committee of the Russian Federation for standardization, Metrology and certification from January 2, 1997, 204 N interstate standard GOST 25284.4−95 was put into effect directly as the state standard of the Russian Federation from January 1, 1998

4 REPLACE GOST 25284.4−82

1 SCOPE

This standard applies to zinc alloys, and sets the photometric (with a mass fraction of lead from 0.002 to 0.05%) and atomic absorption (at a mass fraction of lead of 0.0025 to 0.05%) methods for determination of lead in samples of these alloys.

2 NORMATIVE REFERENCES

The present standard features references to the following standards:

GOST 3118−77 hydrochloric Acid. Specifications

GOST 3760−79 Ammonia water. Specifications

GOST 3778−77* Lead. Specifications
________________
* On the territory of the Russian Federation GOST 3778−98. Here and further. — Note the manufacturer’s database.

GOST 4165−78 Copper (II) sulfate 5-water. Specifications

GOST 4328−77 Sodium hydroxide. Specifications

GOST 4461−77 nitric Acid. Specifications

GOST 5817−77 tartaric Acid. Specifications

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

GOST 10929−76 Hydrogen peroxide. Specifications

GOST 20015−88 Chloroform. Specifications

GOST 25284.0−95 Alloy zinc. General requirements for methods of analysis

3 GENERAL REQUIREMENTS

General requirements for methods of analysis according to GOST 25284.0.

4 PHOTOMETRIC METHOD

4.1 the essence of the method

The method is based on chloroform extraction of the diethyldithiocarbamate lead from sample solution, the substitution of the cation, lead cation of copper and measuring the optical density of the chloroform solution of diethyldithiocarbamate copper at a wavelength of 430 nm.

4.2 Equipment, reagents and solutions

Spectrophotometer or photoelectrocolorimeter.

Tartaric acid according to GOST 5817, a solution of 500 g/DM.

Hydrochloric acid according to GOST 3118, diluted 1:99.

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

A mixture of acids: nitric and hydrochloric acid mixed in a 1:1 ratio.

The thioacetamide in the normative documentation, solution 20 g/DM.

Iron metal restored according to regulatory documents.

The solution of nitrate of iron: 1 g of metallic iron are dissolved in 20 cmof a solution of nitric acid, transfer the solution into a measuring flask with a capacity of 1 DMand dilute to the mark with water.

Ammonia water according to GOST 3760, diluted 1:14.

Diethyldithiocarbamate sodium GOST 8864, a solution of 10 g/DM.

Copper sulfate anhydrous GOST 4165, a solution of 50 g/DM.

Chloroform according to GOST 20015.

Sodium hydroxide according to GOST 4328, a solution of 500 g/DM.

Lead metal — in GOST 3778.

Standard solutions of lead

Solution a: 0.1 g of lead dissolved in 20 cmof a solution of nitric acid removed the oxides of nitrogen by boiling, the solution was cooled, transferred to a volumetric flask with a capacity of 1 DM, adjusted to the mark with water and mix.

1 cmof the solution contains 0.0001 g of lead.

Solution B: 10 cmsolution And placed in a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

1 cmof solution B has the 0.00001 g of lead.

Phenolphthalein, the normative documentation, solution in ethanol, 1

0 g/DM.

4.3 analysis

4.3.1 the sample of alloy weighing 1 g is placed in a beaker with a capacity of 250 cmand dissolved in 25−30 cmof hydrochloric acid. Upon termination reactions dissolve a few drops of nitric acid for complete dissolution of sample. The solution was evaporated to dryness, add 50 cmof water, 30 cmof a solution of tartaric acid and ammonia dropwise until pH 2 (the pH control is carried out according to universal indicator paper). The solution was poured 1.5−2 cmof hydrochloric acid and water to a volume of 150−200 cm. The solution is heated to 90 °C and add 10 cmof a solution of thioacetamide. Solution and the precipitate is kept in a warm place on the stovetop for 10−15 minutes Then add another 10 cmof a solution of thioacetamide and leave for 12 hours in a warm place for complete coagulation of the precipitate.

The precipitate of the sulphides of copper and lead is filtered out, washed 7−8 times with hydrochloric acid, the precipitate with the filter placed in a porcelain crucible, incinerated and calcined in a muffle furnace at a temperature of 600 °C. the Calcined residue was cooled, dissolved in a Cup of 5−6 cmof the mixture of acids, transfer the solution into a glass with a capacity of 400 cm. Top up with water up to 70 cmadd 30 cmof a solution of nitrate of iron, add water up to 150−200 cm, heated to 80−90 °C. and add ammonia to the formation of copper-ammonia complex placed in a warm place for 15−20 min until complete coagulation of the precipitate. The precipitate was filtered off on a medium density filter (white ribbon) and washed first with hot ammonia solution, and then 2−3 times with hot water.

Funnel to precipitate hydroxides were placed in a glass, which conducted the deposition, and dissolve the filter cake in 20 cmof hot nitric acid solution, rinse the filter 2−3 times with hot water. To the solution add water to 150−200 cm, heated to 80−90 °C and perform the procedure perioadele to complete removal of copper from solution (test solution of sodium diethyldithiocarbamate in chloroform for complete removal of copper in the filtrate). After removal of copper from the solution the precipitate is dissolved in 10 cmhot solution of nitric acid in the glass, which conducted the deposition. The solution was boiled to remove oxides of nitrogen and

cool.

4.3.2 When the mass fraction of lead from 0.002 to 0.01% solution transferred to a separatory funnel with a capacity of 500 cm.

4.3.3 for the mass concentration of lead in excess of 0.01% solution was transferred to volumetric flask with a capacity of 50 cm, made up to the mark with water and mix.

10 cmsolution placed in a separatory funnel with a capacity of 500 cm.

4.3.4 In a separatory funnel with the solution obtained in 4.3.2 or 4.3.3, add 100 cmof water, 20 cmof a solution of tartaric acid, 2−3 drops of phenolphthalein and neutralize with sodium hydroxide solution until the appearance of pink coloring and added another 5 cmof sodium hydroxide solution. Add 5 cmof a solution of sodium diethyldithiocarbamate, 15 cmof chloroform and shake for 5 min.

After phase separation, the lower chloroform layer is drained into another separatory funnel with a capacity of 150 cmso that the funnel did not get an aqueous solution.

To the remaining aqueous phase, add another 5 cmof chloroform, shake for 3 min and after phase separation, the chloroform layer attached to the first extract. To the combined extracts add 20 cmof a solution of copper nitrate and shake for 5 min. After separation of the phases of colored chloroform layer is separated and filtered through a medium density filter (white ribbon) in a volumetric flask with a capacity of 25 cm, the filter was washed with chloroform, adjusted to the mark with chloroform, and paramashiva

yut.

4.3.5 To build a calibration curve in five of the six separating funnels capacity of 250 cm, each is placed 2,0; 4,0; 6,0; 8,0 and 10,0 cmstandard solution B. To each funnel add water up to 100 cm, 15 cmof a solution of tartaric acid and then act as specified in 4.3.4.

4.3.6 Measure the optical density of the sample solution and solutions for constructing the calibration curve at a wavelength of 430 nm. Solution comparison is the solution, prepared according to 4.3.5 and does not contain lead.

According to the obtained values of optical density and corresponding weight values of lead to build a calibration curve in the coordinates: the optical density is the mass of lead,

4.4 Processing of results

4.4.1 Mass fraction of lead , %, is calculated by the formula

, (1)

where is the mass of lead was found in the calibration schedule g;

 — the weight of the portion of sample or the mass of the sample in aliquote part of the sample solution,

4.4.2 Discrepancy between the results of parallel measurements and the results of the analysis shall not exceed allowable (at confidence probability of 0.95) of the values given in table 1.


Table 1 percentage

5 ATOMIC ABSORPTION METHOD

5.1 the essence of the method

The method is based on dissolving the samples in hydrochloric acid and measuring the nuclear absorption of lead in the flame of acetylene-air at a wavelength of 217,0 or is 283.3 nm.

5.2 the Instrument, reagents and solutions

Atomic absorption spectrophotometer.

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

Hydrochloric acid according to GOST 3118, diluted 1:1, and a solution of 2 mol/DM.

Hydrogen peroxide according to GOST 10929.

Lead metal according to GOST 3778.

Standard solutions of lead

Solution a: 0.5 g of lead dissolved in 20 cmof a solution of nitric acid, the solution was cooled, transferred to a volumetric flask with a capacity of 1 DM, made up to the mark with water and mix.

1 cmof the solution contains 0.0005 g of lead.

Solution B: 20 cmsolution And placed in a volumetric flask with a capacity of 100 cm, add 10 cmsolution (2 mol DM) hydrochloric acid, made up to the mark with water and mix.

1 cmof a solution contains 0.0001 g pig

CA.

5.3 analysis

5.3.1 Sample the sample weight of 2 g were placed in a glass with a capacity of 300 cm, add 20 cmof a hydrochloric acid solution (1:1). After the reaction, dissolved add 2 cmof hydrogen peroxide and boil for 5 minutes the Solution was cooled.

5.3.2 When the mass fraction of lead of 0.02% solution transferred to a volumetric flask with a capacity of 50 cm, made up to the mark with water and mix.

5.3.3 for the mass concentration of lead in excess of 0.02% 25 cmof the solution prepared in accordance with 5.3.2, is placed in a volumetric flask with a capacity of 50 cm, made up to the mark with water and mix.

5.3.4 To build a calibration curve in six of the seven volumetric flasks with a capacity of 50 cmeach is placed 0,5; 1,0; 2,0; 3,0; 4,0 and 5,0 cmstandard solution B. In each flask add 10 cmof solution (2 mol DM) hydrochloric acid, made up to the mark with water and mix.

The solution to which is not entered lead, serves as a solution control experience.

5.3.5 sample Solutions, control, experience and solutions to build the calibration curve is sprayed into the flame of acetylene-air and measure the atomic absorption of lead at a wavelength is 283.3 nm or 217,0 nm.

According to the obtained values of the nuclear absorption and the corresponding lead concentrations to build a calibration curve in the coordinates: the value of atomic absorption — mass concentration of lead, g/cm.

Mass concentration of lead in the sample solution and the solution of control and experience determined by the calibration schedule.

5.4 processing of the results

5.4.1 Mass fraction of lead , %, is calculated by the formula

, (2)

where is the mass concentration of lead in the sample solution found by the calibration schedule, g/cm;

 — mass concentration of lead in solution in the reference experiment, was found in the calibration schedule, g/cm;

 — the volume of the sample solution, cm;

 — the weight of the portion of sample or the mass of the sample in aliquote part of the sample solution, g

.

5.4.2 Discrepancy between the results of parallel measurements and the results of the analysis shall not exceed allowable (at confidence probability of 0.95) of the values given in table 1.