GOST 25284.8-95

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  ГОСТ 25284.8-95

GOST 25284.8−95 Alloy zinc. Methods for determination of silicon

GOST 25284.8−95

Group B59

INTERSTATE STANDARD

ZINC ALLOYS

Methods for determination of silicon

Zinc alloys. Methods for determination of silicon

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 (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 dated June 2, 1997 N 204 inter-state standard GOST 25284.8−95 was put into effect directly as the state standard of the Russian Federation from January 1, 1998

4 REPLACE GOST 25284.8−84

1 SCOPE

This standard applies to zinc alloys, and sets the photometric methods for determination of silicon with ascorbic acid (at a mass fraction of silicon of from 0.01 to 0.1%) and ferrous sulfate (II) (if the mass fraction of silicon of from 0.005 to 0.04%) in samples of these alloys.

2 NORMATIVE REFERENCES

The present standard features references to the following standards:

GOST 83−79 Sodium carbonate. Specifications

GOST 859−78* Copper. Brand
________________
* On the territory of the Russian Federation GOST 859−2001. Here and further. — Note the manufacturer’s database.

GOST 3640−94 Zinc. Specifications

GOST 3760−79 Ammonia water. Specifications

GOST 3765−78 Ammonium molybdate. Specifications

GOST 4148−78 Iron (II) sulphate 7-aqueous. Specifications

GOST 4204−77 sulfuric Acid. Specifications

GOST 4328−77 Sodium hydroxide. Specifications

GOST 4461−77 nitric Acid. Specifications

GOST 9428−73 Silicon (IV) oxide. Specifications

GOST 9656−75 boric Acid. Specifications

GOST 10484−78 hydrofluoric Acid. Specifications

GOST 11069−74* Aluminium primary. Brand
________________
* On the territory of the Russian Federation GOST 11069−2001. Here and further. — Note the manufacturer’s database.

GOST 18300−87 ethyl rectified technical. Specifications

GOST 20478−75 Ammonium neccersarily. Specifications

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

3 GENERAL REQUIREMENTS

General requirements for methods of analysis GOST 25284.0.

4 PHOTOMETRIC METHOD WITH ASCORBIC ACID (AT A MASS FRACTION OF SILICON OF FROM 0.01 TO 0.1%)

4.1 the essence of the method

The method is based on formation of yellow forms kremneftoristogo acid at pH 1−2, the restoration of its ascorbic acid to form blue and measuring optical density of the resulting solution at a wavelength of 675 nm.

4.2 Equipment, reagents and solutions

Spectrophotometer or photoelectrocolorimeter.

Nitric acid according to GOST 4461, diluted 1:2.

Sulfuric acid according to GOST 4204, a solution of 4 mol/DM: 225 cmof sulphuric acid of density 1.84 g/cmcarefully, thin stream, with stirring and cooling, pour into a glass with a capacity of 1 DMcontaining 500 cmof water, cooled, transferred to a volumetric flask with a capacity of 1 DM, adjusted to the mark with water and mix.

Hydrofluoric acid according to GOST 10484.

Zinc GOST 3640.

Copper grade MO according to the GOST 859.

Aluminum brand А999 according to GOST 11069.

Boric acid according to GOST 9656, saturated solution: to 60 g of boric acid poured 1 DMwater and stirred. The resulting system is «saturated solution of boric acid crystal, boric acid» is stored in a plastic container.

Ammonium molybdate according to GOST 3765, recrystallized a solution of 50 g/DM: 50 g of finely ground ammonium molybdate is added in small portions to the 700−800 cmof boiling water, stirred until dissolved and cooled. The appearance of white turbidity are added dropwise ammonia until its dissolution, but not longer than until the appearance of a weak odor of ammonia. The solution volume was adjusted with water to 1 DM. After day of standing the solution is filtered through a double filter. Store in a plastic container.

For recrystallization 250 g ammonium molybdate was placed in a beaker with a capacity of 1 DM, pour 400 cmof water, heated to a temperature of 80 °C, dissolved with stirring, ammonia is added to the appearance of obvious odor of ammonia and the hot solution is filtered through a dense filter («blue ribbon») in a glass contains 300 cmof ethanol.

The solution was cooled to 10 °C and allowed to stand for 1 h. the Precipitated crystals are filtered off through a Buchner funnel, sucking mother liquor through the filter medium density («white ribbon»).

The crystals are washed 2−3 times with ethanol in portions of 30 cm, after which they are spread evenly on a sheet of filter paper, cover the second sheet and dried in air.

Ammonia water according to GOST 3760.

Ethanol technical rectified according to GOST 18300.

Of anhydrous sodium carbonate according to GOST 83.

Silicon (IV) oxide according to GOST 9428.

Standard solutions of silicon

Solution a: 0,1070 g of silicon oxide (IV), previously calcined in a muffle furnace at 1000 °C for 30 min, placed in a platinum crucible, add 3 g of sodium carbonate and fused at 700−750 °C to obtain a transparent mass.

After cooling to room temperature, the melt leached with water, the resulting solution was transferred to volumetric flask with a capacity of 1 DM, made up to the mark with water and mix. The solution was stored in a plastic container.

1 cmof solution A contains of 0.00005 g of silicon.

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. The solution is prepared immediately before use and stored in a plastic container.

1 cmof solution B contains 0,000005 g of silicon.

Ascorbic acid medical, solution 50 g/DM, sweep

prigotovleny.

4.3 analysis

4.3.1 the sample of alloy weighing 1 g is placed in a platinum, PTFE Cup or a Cup of glassy carbon and dissolved in 12 cmof nitric acid solution under low heat, covering the Cup with a lid. After clarification of the solution, the Cup is removed from the plate and add 10 drops of hydrofluoric acid. Add a Cup of 30 cmof a saturated solution of boric acid, 50 cmof water and transferred the solution into a measuring flask with a capacity of 100 cm(with a mass fraction of silicon of from 0.01 to 0.05%) or in a volumetric flask with a capacity of 200 cmcontaining 30 cmof a saturated solution of boric acid (with a mass fraction of silicon in excess of 0.05%). The solution in the flask was adjusted to the mark with water and mix. At the same time spend control experience.

4.3.2 Two aliquote part of the solution to 10 cm,transferred to volumetric flasks with a capacity of 50 cm. The solution in one flask topped up to the mark with water and mix (solution comparison). The second flask is poured water to a volume of approximately 40 cm, set pH of 1−2 by pH meter or universal indicator paper with a solution of sulfuric acid (4 mol/DM) is added 1 cmof ammonium molybdate solution, mix and leave for 10 minutes, add 2 cmof sulfuric acid solution (4 mol/DM), is stirred, is added 1 cmof ascorbic acid, adjusted to the mark with water and mix. After 20 minutes, measure the optical density of the solution at a wavelength of 675 nm in a cuvette with the thickness of the absorbing layer 2 with

M.

4.3.3. To build a calibration chart, a portion of the mixture in accordance with table 1 was placed in a platinum, PTFE Cup or a Cup of glassy carbon and dissolved in 12 cmof a solution of nitric acid when heated, covered the Cup with a lid.


Table 1

After dissolution of copper and zinc, the Cup is removed from the heat, add 10 drops of hydrofluoric acid and heated until complete dissolution of aluminium. The Cup is removed from the plate, add 10 cmof a saturated solution of boric acid, 50 cmof water and transferred the solution into a measuring flask with a capacity of 100 cmcontaining 20 cmof a saturated solution of boric acid, add the solution to the mark with water and mix. In six volumetric flasks with a capacity of 50 cmeach are placed 10 cmmixture solution, five of them add 1,0; 3,0; 5,0; 7,0 and 10,0 cmstandard solution, add water to volume of approximately 40 cmand then do as described in section 4.3.

2.

4.4 Processing of results

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

, (1)

where is the mass of silicon in aliquotes of the samples was found in the calibration schedule g;

 — the mass of silicon in the solution in the reference experiment, was found in the calibration schedule g;

 — weight of sample, g;

10 — aliquota part of the solution, cm;

100 or 200 — the volume of the sample solution, cm

.

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 2.


Table 2

Percentage

5 PHOTOMETRIC METHOD, IRON SULFATE (II) (IF THE MASS FRACTION OF SILICON OF FROM 0.005 TO 0.04%)

5.1 the essence of the method

The method is based on formation of yellow forms kremneftoristogo acid in an acidic environment, restoring it with a solution of iron sulfate (II) to the blue form and measurement of the optical density of the resulting solution at a wavelength of 675 nm. Definition of silicon in preventing phosphate — and arsenate-ions.

5.2 the Instrument, reagents and solutions

Spectrophotometer or photoelectrocolorimeter.

Nitric acid according to GOST 4461, diluted 1:3.

Sulfuric acid according to GOST 4204, diluted 1:3, 1:4 and 1:99.

Ammonium molybdate according to GOST 3765, recrystallized, solution 50 g/DM. Prepared in accordance with 4.2.

Iron (II) sulfate according to GOST 4148, a solution of 40 g/DM: 40 g of salt dissolved in 500 cmof water, mixed with 500 cmof sulphuric acid, diluted 1:4.

Ammonium neccersarily according to GOST 20478, a solution of 10 g/DM, freshly prepared.

Sodium hydroxide according to GOST 4328, a solution of 250 g/DM. Store in a plastic container.

Of anhydrous sodium carbonate according to GOST 83.

Silicon (IV) oxide according to GOST 9428.

A standard solution of silicon (IV):

0,1070 g of silicon oxide (IV), previously calcined in a muffle furnace at 1000 °C for 30 min, placed in a platinum crucible and fused with 2 g of anhydrous sodium carbonate in a muffle furnace at a temperature of 700−750 °C to obtain a transparent mass. After cooling to room temperature, the melt leached with water, the resulting solution was transferred to a volumetric flask with a capacity of 500 cm, made up to the mark with water and mix. The solution was stored in a plastic container.

1 cmof the solution contains 0.0001 gram of silicon.

Zinc GOST 364

0.

5.3 analysis

5.3.1 a sample of alloy weighing 2 g was placed in a platinum, PTFE Cup or a Cup of glassy carbon and dissolved in 40 cmof a solution of nitric acid. The solution is heated to remove oxides of nitrogen, add 5 cmof a solution of ammonium persulfate and boil for another 5 min. the Solution was cooled, transferred to a volumetric flask with a capacity of 100 cm, is diluted to the mark with water and mix.

5.3.2 Aliquot part of the solution is 5 cm,transferred to a volumetric flask with a capacity of 50 cm, flow 10 cmof sulfuric acid solution (1:99), added dropwise a solution of sodium hydroxide to pH 1.6 pH-meter. Add 5 cmof ammonium molybdate solution, mix. After 3 min add 10 cmsulphuric acid (1:3) and after 1 min. dilute to the mark with a solution of iron sulfate (II). After 5 min measure the optical density of the solution at a wavelength of 675 nm in a cuvette with the thickness of the absorbing layer 2 see Solution comparison is the solution of the reference experiment in which no was added to a solution of molybdate of ammonium.

5.3.3 For construction of calibration curve six platinum fluoroplastic cups or cups of glassy carbon put a sample of zinc with a mass of 2 g. five cups consistently poured 1,0; 3,0; 5,0; 7,0 and 9,0 cmstandard solution silicon, 40 cmof a solution of nitric acid and then act as described in 5.3.

5.4 processing of the results

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

, (2)

where is the mass of silicon in aliquotes of the samples was found in the calibration schedule g;

5 — volume aliquote parts of a solution of the sample, cm;

 — weight of sample, g;

100 — volume of sample solution, cm.

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 3.


Table 3

Percentage