GOST 1762.7-71

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  ГОСТ 1762.7-71

GOST 1762.7−71 Silumin ingots. Methods for determination of zinc (with Amendments No. 1, 2)

GOST 1762.7−71

Group B59

STATE STANDARD OF THE USSR

SILUMIN IN PIGS

Methods for determination of zinc

Aluminium-silicon alloy ingots.
Methods for determination of zinc

AXTU 1709

Valid from 01.01.73
to 01.07.95*
_______________________________
* Expiration removed
Protocol N 4−93 inter-state Council
for standardization, Metrology and certification.
(IUS N 4, 1994). — Note the «CODE»

INFORMATION DATA

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

THE DEVELOPERS OF THE STANDARD

A. A. Kostyukov, G. A. Romanov, N. M. Gertseva, A. P. Nechitailov, V. A. Lavrov

2. APPROVED AND promulgated by the Decree of the State Committee of standards of Ministerial Council of the USSR from 08.10.77 N 141

3. The frequency of inspection — 5 years

4. REPLACE GOST 1762−51 (in terms of sec. VIII)

5. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

6. Validity extended until 01.07.95 by the Resolution of Gosstandart of the USSR from 27.03.89 N 492

7. The re-release (may 1989) with Amendments No. 1, 2 approved in August 1984, March 1989 (IUS 12−84, 6−89)


This standard specifies the photometric (with a mass fraction of zinc from of 0.004 to 0.09%), polarographic (mass fraction of 0.005 at 0.1%) and atomic absorption methods for the determination of zinc (at a mass fraction of zinc from 0.01 to 0.075%).

(Changed edition, Rev. N 2).

1. GENERAL REQUIREMENTS

1.1. General requirements for methods of analysis GOST 1762.0−71.

2. PHOTOMETRIC METHOD

2.1. The method is based on measuring the optical density of the colored complex compounds of zinc with dithizone is extracted with carbon tetrachloride. The effect of copper and other elements is eliminated by preliminary extraction dithizonate at pH<2, masking with sodium diethyldithiocarbamate, binding of the aluminum citrate complex.

(Changed edition, Rev. N 2).

2.2. Apparatus, reagents and solutions

Photoelectrocolorimeter FEK-56M, PEC-60, KLF, spectrophotometer SF-16, SF-26 or similar.

Distilled water not containing heavy metals. Water is purified by passing through a layer of cation exchange resin (KU-1, KU-2), prepared as described in GOST 1762.6−71.

The cation exchanger KU-1, KU-2 according to GOST 20298−74.

All the solutions were prepared in purified in such way water.

Ammonia water according to GOST 3760−79 and diluted 1:40, cleaned. The purified ammonia is prepared by saturating with ammonia vapour purified water. To do this, in the desiccator, pour ammonia solution on the liner of the dryer is placed a quartz or platinum dish with purified water. After 24 h water saturated with ammonia. Keep ammonia in a quartz or plastic container.

Hydrochloric acid by the GOST 3118−77, diluted 1:2, 1:5.

Carbon tetrachloride according to GOST 20288−74.

Ditson (definitionalism) according to GOST 10165−79, solutions with a mass fraction of 0.01 and 0.002% in carbon tetrachloride; the solution with a mass fraction of 0.01% is prepared as follows: 0.05 g of dithizone dissolved in 100 cmof carbon tetrachloride, transfer the solution into the separatory funnel with a capacity of 1000 cm, pour 200 cmwater, 5 cmof ammonia solution and the contents of the funnel vigorously shaken for 1−2 min Decison goes into odnoimennyi layer, colouring it orange. The solution was then defending until the disappearance of the emulsion and separate the layers. The layer of carbon tetrachloride is discarded.

To the ammonia solution in a separating funnel pour 200 cmof carbon tetrachloride, acidifying with hydrochloric acid, diluted 1:5, and periodically shake the contents of the funnel to the disappearance of the orange color of the water layer and transfer dithizone in the organic layer. Solution dithizone in carbon tetrachloride, painted green, is separated from the water layer, washed twice with water and filtered through a dry folded filter paper into a dry flask of dark glass. Then pour the 300 cmof carbon tetrachloride and stirred. Store the solution in a cool place. When storing ditson partially oxidized giving colored products.

Before analysis to check the suitability of the solution dithizone, shaking it with diluted ammonia. The layer of carbon tetrachloride should not be painted; otherwise, a second cleaning solution dithizone as described above.

A solution with a mass fraction of 0,002 ditizona% prepared before use from a solution with a mass fraction of 0.01%, diluting it with carbon tetrachloride.

The technical rectified ethyl alcohol GOST 18300−87.

NTD phenolphthalein in alcohol solution with a mass fraction of 1%.

Ammonium disodium citrate according to GOST 3653−78, 0.5 mol/lpurified solution. Purify as follows: to the solution add a few drops of phenolphthalein and pour ammonia until the appearance of crimson color. The solution is purified by extraction portions of a solution with a mass fraction of ditizona of 0.01%. The extraction is repeated to produce the same green color of the extract. The last portion of the test the content of heavy elements. This excess dithizone removed by shaking the extract with 30−40 cmof dilute ammonia. The layer of carbon tetrachloride should be colorless. To retrieve ditizona passed into a solution of citrate of ammonium, the latter is shaken out with several portions of carbon tetrachloride.

Sodium citrate according to GOST treasuremania 22280−76 solution with a mass fraction of 50%, clean as well as ammonium citrate.

Diethyldithiocarbamate sodium GOST 8864−71, a freshly prepared solution with a mass fraction of 0.2%.

Solution a, prepared as follows: to 100 cmof a solution of 0.5 mol/DMammonium citrate is added ammonia to a crimson colour and diluted with water to 450 cm.

Solution B, prepared as follows: solution with a mass fraction of 0.2% sodium diethyldithiocarbamate is mixed with solution A in the ratio 1:9.

Sodium sulfide (sodium sulfide) according to GOST 2053−77 solutions with a mass fraction of 1 and 0.05%. The latter is prepared by dilution of a solution with a mass fraction of 1% before use.

Metanolovyj yellow, aqueous solution with a mass fraction of 0.1%.

Zinc metal according to GOST 3640−79*.
________________
* Valid GOST 3640−94, here and hereafter. — Note the CODE.

Standard solutions of zinc

The solution, prepared as follows: of 0.2000 g of zinc is dissolved in 15 cmof hydrochloric acid, diluted 1:2. The solution was transferred to volumetric flask with a capacity of 1 DM, dilute to the mark with water and mix.

1 cmof solution A contains 0.2 mg of zinc.

A solution of G, prepared before use by diluting the solution 100 times with water.

1 cmsolution G contains 0.002 mg of zinc.

Sodium sulphate anhydrous according to GOST 4166−76.

(Redrafted From

M. N 1).

2.3. Analysis

2.3.1. For analysis using the solution prepared according to claim 2.3.1 GOST 1762.6−71.

Depending on the zinc content of the volumetric flask with a capacity of 250 cm5−25 cm takethe solution in separating funnel capacity of 250 cm, pour 1−2 cmof solution with a mass fraction of sodium citrate 50%, 2−3 drops methylophaga yellow, and dilute with water to 40 cm. Then neutralized with ammonia to dye indicator is yellow and hydrochloric acid diluted 1:5 before staining to slightly pink color.

Poured from a burette 5 cmsolution with a mass fraction of dithizone 0.002% and vigorously shaken for 3−5 min. After a short settling diisononyl layer is discarded and extracted with a new portion of dithizone (5 cm) for 3 min. If necessary, extraction is repeated until the same coloring ditizona. The organic layer is again discarded. Dropping dimitrovova layer do not allow the passage of the aqueous phase into the opening of the valve.

To the solution in separating funnel was added 40 cmof a solution, a few drops of phenolphthalein and, if necessary, ammonia is added to the appearance of crimson color. Then from a burette add 10 cmof a solution with a mass fraction of dithizone 0.1%, and vigorously shaken for 2 min. After a short settling, the layer of carbon tetrachloride is transferred to a dry cylinder with a glass stopper. Repeat the extraction two more times using 10 and 5 cmsolution dithizone. The total volume of solution dithizone used to determine the content of zinc is 25 cm.

Then remove the excess by shaking dithizone dimitrovova extract with a solution with a mass fraction of sodium sulfide to 0.05%. To do this, 2−3 separating funnels capacity of 250 cmpour 10 cmof solution with a mass fraction of sodium sulfide to 0.05%, one of them transferred the contents of the cylinder and shake 3−4 times. The layer of carbon tetrachloride is transferred into the next funnel. This operation is repeated until then, until the aqueous layer will remain colorless. Then washed with a solution of zinc dithizonate by shaking with water and transferred it into the cylinder with a glass stopper. Solution dithizonate in the cylinder should be protected from light.

Not later than 15−20 minutes after the laundering of excess dithizone measure the optical density of the solution on the photoelectrocolorimeter or spectrophotometer, given that a maximum light absorption of the solution corresponds to a wavelength of 538 nm. Solution comparison is carbon tetrachloride.

To remove residual moisture during the filling of the cuvette the solutions were passed through a dry ash-free filter or the extracts in the cylinders was added 1 g of anhydrous sodium sulfate.

The zinc content find for the calibration g

Rafik.

2.3.2. Construction of calibration curve

In a separating funnel with a capacity of 250 cmpoured in 30 cmof water, 2 cmof solution with a mass fraction of sodium citrate 50%, 2−3 drops yellow and methylophaga from burette 0; 1,0; 2,0; 2,5; 3,0; 3,5; 4,0; 4,5 cmstandard solution G, which corresponds to 0; 0,002; 0,004; 0,005; 0,006; 0,007; 0,008, 0,009 mg of zinc. Then set the environment by metaniobate yellow and then carry out the analysis as described in section 2.3.1.

Solution comparison is carbon tetrachloride.

According to the obtained values of optical density and known concentration of zinc in solutions to build the calibration graph.

2.4. Processing of the results

2.4.1. Mass fraction of zinc () in percent is calculated by the formula

,

where is the mass of zinc that was found in the calibration graphics mg;

 — the total volume of solution, cm;

 — volume aliquote part of the solution, cm;

 — the weight of the portion of silumin,

2.4.2. Allowable absolute differences of the results of the parallel definitions should not exceed the values given in table.1.

Table 1

(Changed edition, Rev. N 2).

3. POLAROGRAPHIC METHOD

3.1. The essence of the method

The method is based on dissolving the alloy in sodium hydroxide solution, acidification of the alkaline solution bromatological acid to pH 1 and polarographically zinc in the range of potentials from minus 0.6 to minus 1.0 V.

3.2. Apparatus, reagents and solutions

Polarograph AC type PU-1 or similar.

Nitrogen gaseous and liquid technical, GOST 9293−74 or argon gaseous and liquid GOST 10157−79.

Sodium hydroxide according to GOST 4328−77, a solution with a mass fraction of 20%.

Bromatologia acid according to GOST 2062−77, diluted 2:1.

Bromine according to GOST 4109−79.

Freshly prepared ascorbic acid solution with a mass fraction of 25%.

Zinc metal according to GOST 3640−79.

Standard solutions of zinc: 1,0000 g of zinc were placed in a glass with a capacity of 250 cm, 30 cm pournitric acid, diluted 1:1. After the dissolution of the zinc wall of the beaker is washed with water, the solution was cooled, transferred into a measuring flask with volume capacity of 1000 cm, adjusted to the mark with water and mix.

1 cmof the solution contains 1 mg of zinc.

By appropriate dilution (before applying) prepare a solution with A concentration of zinc of 0.1 mg per 1 cmof the solution and solution B with a concentration of zinc of 0.01 mg per 1 cmof solution.

3.3. Analysis

3.3.1. A portion of the silumin weighing 0.5 g were placed in a glass with a capacity of 100 cm, flow 15 cmof sodium hydroxide solution and cover glass. At the end of the reaction the solution was boiled for 5 min to dissolve the alloy, cooled, diluted with water to a volume of 20 cmand carefully poured 30 cmbromatological acid. The solution is heated to enlightenment. After a slight cooling, add 2−3 drops of bromine and again heated to remove excess bromine, bringing the solution volume to 45 cm. Then added dropwise a solution of ascorbic acid to the bleaching solution. The cooled solution was transferred to volumetric flask with a capacity of 50 cm, made up to the mark with water and mix.

3.3.2. Construction of calibration curve (with a mass fraction of zinc from 0.005 to 0.02%)

Three cups with a capacity of 25 cmconsistently poured 0,5; 1,0; 2,0 cmstandard solution B, which corresponds to 0,005; 0,01; 0,02% zinc. The solutions were evaporated to dryness on a water bath to the dry residue add aliquot part 10 cmof one of the studied solutions with a lower content of zinc, stirring of the solution placed in the cell and polarographic under the same conditions as described in section 3.3.1.

From the obtained heights of the peaks subtract the peak height of the investigated diluted solution.

According to the obtained results and the known concentrations of zinc build a calibration curve.

When you replace the capillaries, you need to check the schedule.

3.3.3. Construction of calibration curve (with a mass fraction of zinc from 0.01 to 0.1%)

Three cups with a capacity of 25 cmconsistently poured 0,1; 0,5; 1,0 cmstandard solution A, which corresponds to 0.01; 0.05 and 0.1% zinc. Then do as stated in claim 3.3.2.

3.4. Processing of the results

Mass fraction of zinc () in percent is determined according to the calibration schedule.

3.4.1. Allowable absolute differences of the results of the parallel definitions should not exceed the values given in table.2.

Table 2

(Changed edition, Rev. N 2).

4. ATOMIC ABSORPTION METHOD

4.1. The essence of the method

The method is based on the measurement of atomic absorption of zinc in the flame of acetylene-air at a wavelength of 213,8 nm.

4.2. Apparatus, reagents and solutions

Spectrometer atomic absorption model of Perkin-Elmer, «Saturn» or similar.

Lamp with a hollow cathode, is intended for the determination of zinc.

Acetylene in cylinders for technical GOST 5457−75.

Muffle furnace with thermostat, providing a temperature of 1000 °C.

Hydrochloric acid by the GOST 3118−77, diluted 1:1.

Hydrogen peroxide according to GOST 10929−76, a solution with a mass fraction of 3%.

Aluminium stamps A-999 according to GOST 11069−74*.
________________
* On the territory of the Russian Federation GOST 11069−2001. — Note the CODE.

The solution of aluminum And 20 g/l: 10.0 g of aluminum is placed in a beaker with a capacity of 600 cm, add 250 cmof hydrochloric acid diluted 1:1, and dissolved under heating with adding 1 cmof solution of chloride Nickel. The solution was cooled, transferred to a volumetric flask with a capacity of 500 cm, is diluted to the mark with water and mix.

Nickel chloride according to GOST 4038−79, a solution with a mass fraction of 0.2%.

Sodium carbonate according to GOST 83−79.

Silicon dioxide according to GOST 9428−73.

A solution of silicon B, 1 g/DM: 2,14 g of finely crushed in an agate or plexiglass mortar and preheated for one hour at a temperature of 1000 °C silicon dioxide is fused in a platinum crucible with 15.0 g of sodium carbonate at a temperature of 900 °C for 15 min to obtain clear water. The smelt is dissolved in water under heating. The solution was transferred into a measuring flask with volume capacity of 1000 cm, is diluted to the mark with water and mix. The solution was stored in a plastic container.

Sodium chloride according to GOST 4233−77.

A solution of sodium oxide, 100 g/l: 190 g dried at 105 °C for 30 min. sodium chloride dissolved in water. The solution was transferred into a measuring flask with volume capacity of 1000 cm, adjusted to the mark with water and mix.

Sodium hydroxide according to GOST 4328−77, a solution with a mass fraction of 30%.

Zinc metal according to GOST 3640−79.

Standard solutions of zinc

Solution D: 0,5000 g of zinc metal are dissolved in 50 cmof hydrochloric acid diluted 1:1. The solution was transferred to volumetric flask with a capacity of 500 cm, was adjusted to the mark with water and mix.

1 cmof solution e contains 1 mg of zinc.

Solution: pipetted 5 cmof solution D in a volumetric flask with a capacity of 200 cm, adjusted to the mark with water and mix; prepare before use.

1 cmof solution E contains 0,025 mg of zinc.

Methyl orange, solution with a mass fraction of 0.1%.

4.3. Analysis

4.3.1. Weighed samples of the silumin weighing 0.5 g were placed in a glass with a capacity of 250 cmand poured 20 cmof the sodium hydroxide solution. After the violent reaction solution is heated until complete dissolution of the alloy, adding 100 cmof water and carefully to the cooled solution poured 50 cmof hydrochloric acid diluted 1:1. The solution is heated to enlightenment, add 1 cmof hydrogen peroxide and boiled for 3−5 min for the destruction of its excess. The solution was cooled, transferred to a volumetric flask with a capacity of 250 cm, was adjusted to the mark with water and mix.

Simultaneously carried through all stages of the analysis test experience using all the reagents, with the addition of 20 cmof a solution of aluminium A.

Measure the atomic absorption of zinc in the sample solution, the solution in the reference experiment and in solutions, prepared to build a calibration curve at a wavelength of 213,8 nm in the flame acetylene-air.

Mass fraction of zinc is determined according to the calibration schedule, which build on every shot

.

4.3.2. Construction of calibration curve

In seven volumetric flasks with a capacity of 250 cmpoured in 12.5 cmof solution A with 7 cmof solution, respectively, to each flask 0; 2,0; 4,0; 6,0; 8,0; 10,0; 15,0 solution E, which corresponds to 0; 0,01; 0,02; 0,03; 0,04; 0,05; 0,075% mass fraction of zinc in silumin. The solutions were adjusted with water to a volume of 100 cmand slowly portions, stirring thoroughly, pour 25 cmof a solution, pour 3−4 drops of methyl orange indicator and drop hydrochloric acid diluted 1:1, until the color changes of the indicator in red. Then the solutions in the flasks was adjusted to the mark with water, mix and measure the atomic absorption of zinc, as specified in clause 4.3.1.

According to the obtained values of atomic absorption solutions and the known values of the mass fraction of zinc build a calibration curve.

4.4. Processing of the results

4.4.1. Mass fraction of zinc in percent find the calibration schedule, minus the reference experiment.

4.4.2. Permissible discrepancies in the results of parallel definitions should not exceed the values given in table.1.

Sec. 4. (Added, Rev. N 2).