GOST R 50424-92

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  ГОСТ Р 50424-92

GOST R 50424−92 Steel and cast iron. Method of determination of calcium

GOST R 50424−92

Group B39

STATE STANDARD OF THE RUSSIAN FEDERATION

STEEL AND CAST IRON

Method of determination of calcium

Steel and cast iron. Method for determination of calcium

OKS 77.080.01
AXTU 0809

Date of introduction 1994−07−01

INFORMATION DATA

1 DEVELOPED AND SUBMITTED by the Technical Committee for standardization TC 145 «monitoring Methods of steel products"

2 APPROVED AND put INTO effect by the Resolution of Gosstandart of Russia from December 2, 1992 N 1529

3 INTRODUCED FOR THE FIRST TIME

4 REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

5 REISSUE


This standard specifies atomic absorption (in mass fractions of from 0.001 to 0.20%) method for the determination of calcium in steels and cast iron.

The method is based on dissolving the sample in hydrochloric, nitric, fluoric hydrogen and chloric acid; the addition of solutions of potassium chloride and lanthanum nitrate as a spectrochemical buffer, spraying the test solution into the flame dinitroazetidine; spectrometric measuring the absorption values of the radiation emitted by the lamp with hollow cathode, free of calcium atoms at a wavelength 422,7 nm.

1 General requirements

General requirements for methods of analysis GOST 28473.

2 Equipment, reagents and solutions

The atomic absorption spectrometer.

Lamp with hollow cathode for the determination of calcium.

Cylinders dinitrourea and acetylene not containing water, oil and calcium (acetylene purified by passing through geratol or other suitable method).

Beakers, flasks, funnels made of transparent quartz glass according to GOST 19908.

The glasses are made of PTFE with a capacity of 250−300 cm.

Volumetric flasks made of fluoroplastic 4MB with a capacity of 100 cmon the other 95−337.

The cylinders of fluoroplastic 4MB.

Note — All used utensils should be thoroughly washed with hot hydrochloric acid (1:2), and then double-distilled water (tap water for intermediate rinsing is used).


Conventional laboratory equipment.

Bidistilled water according to GOST 4517 or equivalent purity (stored in a vessel made of polyethylene).

Iron is very pure, containing not more than 0.0005% of calcium.

Diethyl ether (ethyl ether medical).

Acid hydrochloric GOST 14261, optionally purified, and diluted 1:2 and 1:9.

Cleaning method: in the desiccator, pour hydrochloric acid on a support is placed a glass made of polyethylene or PTFE, filled with double-distilled or deionized water.

The volume ratio of water and acid should be 1:6. The desiccator tightly closed ground cover. After about four days to get a solution of hydrochloric acid, free from impurities of calcium, with a density of 1.15. Store in polyethylene bottle.

Nitric acid, OS.h. according to GOST 11125.

Perchloric acid, OS.h.

Acid fluoride-hydrogen, the OS.CH., of the highest category.

Potassium chloride, OS.h. on the other 6−09−3678.

Lanthanum nitrate, OS.h.

Spectrochemical buffer: dissolve 95,34 g of potassium chloride and 62,35 g setevogo lanthanum nitrate (La (NO)x6HO) in water and diluted to 1000 cmand mixed. Store the solution in polyethylene bottles.

Calcium carbonate, OS.h. on the other 6−09−895.

Standard solutions of calcium

Solution a: 0,2497 g of calcium carbonate dried at 100 °C for 1 h and cooled in a desiccator to room temperature, placed in a beaker, carefully add 10 cmof hydrochloric acid (1:2), covered with a glass watch glass and dissolve with a moderate heat. The solution was cooled, transferred to a measuring flask with volume capacity of 1000 cm, made up to the mark with water and mix. Store the standard solution in a sealed plastic container.

1 cmof the solution contains 100 mg of calcium.

Solution B: placed 10.0 cmof solution A in a volumetric flask with a capacity of 100 cm, add 5 cm ofhydrochloric acid (1:9), dilute to the mark with water and mix. The solution is prepared immediately before use.

1 cmof solution contains 10 mcg of calcium.

Note — For the preparation of all series of the analyzed samples in the reference experiment and the calibration solutions used reagents, including water, from the same batch.

3 analysis

3.1 the sample the sample washed in diethyl (ethyl) ether and dried, weighing 1,000 g was placed in a Teflon beaker, add 15 cm ofhydrochloric acid, cover with a Teflon cap and dissolved with moderate heating the bulk sample, then add 3−5 cmof nitric acid. After the cessation of violent foaming, add 5 cmof perchloric acid and 3.5 cmfluoride-hydrogen. Continue a moderate heat to release the dense white fumes of perchloric acid.

Perchloric acid can explode in the presence of ammonia, vapour of nitrous acid and any organic reagents.

The solution was cooled, washed wall with water and heating was continued until the termination of allocation of vapors of perchloric acid. Salt dissolved in 5 cmof hydrochloric acid, add 20 cmof water, heated to boiling. The hot solution is filtered into a measuring flask with a capacity of 100 cmthrough a filter of medium density pre-washed 5−6 times with hot hydrochloric acid (1:2) and several times with bidistilled water. The filter cake is washed with hot hydrochloric acid (1:9), add it in small portions until the complete laundering of the filter from iron salts, then washed the filter 3 times more bitter with water and discarded. In the flask, if the expected calcium content does not exceed 0.01%, add 10 cmspectrochemical buffer, made up to the mark with water and mix. In the case that the expected calcium content exceeds 0.01%, the solution in the flask topped up to the mark with water and mix. Then select aliquot part of 10 cmin a volumetric flask with a capacity of 100 cm, add 10 cmspectrochemical buffer, made up to the mark with water and mix.

In parallel with the determination, performing all operations of the methods and using the same quantities of reagents, carry out a test

experience.

3.2 Preparation of the calibration solutions with the mass fraction of calcium to 0.01%

Put seven quartz glasses with a capacity of 250−300 cm1,000 g of iron, add 15 cmof hydrochloric acid and 5 cmof nitric acid. After complete dissolution of the iron solution was evaporated to wet salts and salt dissolved in 5 cmof hydrochloric acid. Add 20 cmof water, bring to the boil, then cooled and transferred to volumetric flask with a capacity of 100 cm. Add standard solution B in accordance with table 1, 10 cmspectrochemical buffer, made up to the mark with water and mix.


Table 1

3.3 Preparation of calibration solutions for the mass concentration of calcium above 0.01%

Put seven quartz glasses with a capacity of 250−300 cm1,000 g of iron, add 15 cmof hydrochloric acid and 5 cmof nitric acid. After complete dissolution of the iron is evaporated to wet salts and salt dissolved in 5 cmof hydrochloric acid. Add 20 cmof water, bring to the boil, then cooled and transferred to volumetric flask with a capacity of 100 cm. Topped up to the mark with water and mix. Select aliquot part of 10 cmin a volumetric flask with a capacity of 100 cm, add standard solution B in accordance with table 1, add 10 cmspectrochemical buffer, made up to the mark with water and paramashiva

yut.

3.4 preparation of the device for measuring

The inclusion and configuration of the atomic absorption spectrometer is carried out according to the instructions supplied with the device.

Basic instrumental parameters

Analytical line 422,7 nm.

Flame — dinitrourea-acetylene. Transparent, stoichiometric with the height of the red cone 10−20 mm, adjusted to the maximum atomic absorption of radiation by atoms of calcium.

Current lamp in accordance with the instructions or 20−25 mA.

The width of the spectral band in accordance with the instructions or between 0.3 and 0.1 mm.

Corrector background — can be used in the case when the absorption is zero the solution has a meaningful value.

Burner — high temperature, with the length of the slit 5, see Before using the slot burner should be cleaned well with a mixture of acetone and ethanol (1:1).

3.5 Spectrometric analysis procedure

3.5.1 Set the lamp current, wavelength, pressure and the initial flow of gases, lit torch, heat it for 5 minutes, then spray water to establish stable results. Adjust flow rates of gases so that the flame was luminous and had a red cone height of about 10−20 mm. is Sprayed, alternately the most concentrated calibration solution and null, while adjusting the gas flow and the burner position (horizontal, vertical, and angled) relative to the light path as long as the difference in absorption value between these solutions will be a maximum. Check the accuracy of the output of the spectrometer at the desired wavelength. Set zero on the registered device unit relative to the water.

Sprayed a full set of calibration solutions, including zero, in ascending order, repeating this operation until the readings will not be stable. Choose two of the calibration solution with a value of absorption is a little lower and a little higher than the test solution. Spray these solutions in ascending or reverse order (the subject in the middle), measuring the absorbance in each case relative to water.

Again spray a complete set of calibration solutions in ascending or reverse order and use average values of absorption for constructing the calibration curve.

In the measurement process, if necessary, clean the burner of soot, if the results show the loss of precision due to contamination of the burner.

Be sure to spray water between the spraying of each solution was measured, making sure that the air intake was minimal.

Mass fraction of calcium in the test sample and the control solution experience find for the calibration schedule.

3.5.2 it is Necessary to prepare a new calibration curve for each series of definitions of calcium and for each interval of the designated contents.

According to the obtained average values of absorbance and corresponding concentrations of calcium, expressed in µg/cmof Sa, build a calibration curve.

Compare the values of the selected absorption of the calibration solutions, which were sprayed before and after test solution, and if these values do not differ from the graphics are more than acceptable standards of accuracy (see table 2), and the value of absorbance of test solution is considered acceptable for determining the calcium concentration, expressed in micrograms/cmof Sa, according to the calibration schedule.


Table 2

4 processing of the results

4.1 the Content of calcium () percentage in the test sample, expressed in mass fractions, calculated by the formula

or in the case of using aliquote part of the solution

,

where is the concentration of calcium in solution in the reference experiment, µ g/cm;

 — calcium concentration in the measured solution, µg/cm;

the volume of the measured solution, cm;

 — the volume of the test solution obtained after dissolution of sample, cm;

 — volume aliquote part of the solution, cm;

 — the weight of the portion of samples

s,

4.2 the Norms of accuracy and norms control the accuracy of determining the mass fraction of calcium are shown in table 2.