GOST 12352-81

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  ГОСТ 12352-81

GOST 12352−81 Steel alloyed and high alloy. Methods for determination of Nickel (with Change No. 1)

GOST 12352−81

Group B39

INTERSTATE STANDARD

STEEL ALLOYED AND HIGH-ALLOYED

Methods for determination of Nickel

Steels alloyed and highalloyed.
Methods for the determination of nickel

AXTU 0809

Date of introduction 1982−01−01

APPROVED AND put INTO EFFECT by Decision of the USSR State Committee for standards from 16.04.81 No. 1997

REPLACE GOST 12352−66 in part of sec. 2, 3

Limitation of actions taken by Protocol No. 2−92 of the Interstate Council for standardization, Metrology and certification (ICS 2−93)

REPRINT (March 1999) with amendment No. 1, approved in July 1986 (IUS 10−86)


This standard specifies methods for the determination of Nickel: photometric (with a mass fraction of from 0.01 to 4.0%), gravimetric (mass fraction in from 0.5 to 45,0%) and atomic absorption (at a mass fraction of from 0.1 to 15.0%) in the alloy and high-alloy steels.

The standard fully complies ST SEV 962−78.

1. GENERAL REQUIREMENTS

1.1. General requirements for methods of analysis GOST 28473−90.

2. THE PHOTOMETRIC METHOD FOR THE DETERMINATION OF NICKEL

2.1. The determination of Nickel (0,01−0,5%) in the steels with a mass fraction of copper to 1%, cobalt up to 1% and manganese up to 2%.

2.1.1. The essence of the method

The method is based on the formation of red color complex compounds of Nickel with dimethylglyoxime in ammoniacal medium in the presence of potassium bromide and Bromeliaceae and measuring the light absorption of the solution at a wavelength of 530 nm.

2.1.2. Equipment and reagents

Spectrophotometer or photoelectrocolorimeter.

Hydrochloric acid by the GOST 3118−77 or GOST 14261−77 and diluted 1:4.

Nitric acid GOST 4461−77 or GOST 11125−84.

Sulfuric acid GOST 4204−77 or GOST 14262−78 and diluted 1:5.

Mixture of nitric and hydrochloric acids in a ratio of 1:3.

Citric acid according to GOST 3652−69, a solution of 100 g/DM.

Potassium bromide according to GOST 4160−74.

Potassium branovitsky according to GOST 4457−74.

A solution of potassium bromide and bromoperoxidase: 39 g of potassium bromide and 10 g of potassium polnovatogo dissolved in water in a volumetric flask with a capacity of 1 DM, made up to the mark with water and mix.

Ammonia water according to GOST 3760−79 and diluted 3:2.

Ethyl alcohol GOST 18300−87.

Dimethylglyoxime according to GOST 5828−77, a solution of 10 g/DMof 10 g dimethylglyoxime was dissolved in ethanol in a volumetric flask with a capacity of 1 DM, made up to the mark with ethanol and mixed, before use, the solution was filtered.

Radio engineering carbonyl iron according to GOST 13610−79.

Nickel metal according to GOST 849−97.

Nickel sulfate, standard solution: 0.1 g of metallic Nickel dissolved in 15−20 cmof nitric acid, poured 30 cmof sulphuric acid (1:5), evaporated prior to the selection of vapors of sulfuric acid and cooled. Salt is dissolved in 100−150 cmof water, the solution transferred to a volumetric flask with a capacity of 1 DM, cooled, made up to the mark with water and mix.

1 cmof the solution contains 0.0001 g Nike

La.

2.1.3. Analysis

Weighed 0.5 g of steel placed in a beaker with a capacity of 200−250 cm, dissolved by heating in 30 cmof sulphuric acid (1:5) and oxidize with nitric acid, adding it drop by drop. If the steel does not dissolve in sulphuric acid (1:5), the sample is dissolved in 30 cmof a mixture of acids. Then pour the 30 cmof sulphuric acid (1:5) and the solution was evaporated prior to the allocation of sulphuric acid fumes. After cooling the salt is dissolved in 100−120 cmof water, the solution transferred to a volumetric flask with a capacity of 250 cm, cooled, made up to the mark with water and mix.

Part of the solution filtered through a dry filter into a flask with a capacity of 250 cm, discarding the first two portions of the filtrate. Aliquote two parts of a solution of 25 cmis placed in a volumetric flask with a capacity of 100 cmand with constant stirring successively poured into each volumetric flask 20 cmof the citric acid solution, 5 cmof hydrochloric acid (1:4), 10 cmof a solution of potassium bromide and Bromeliaceae and 2−3 min of 25 cmof ammonia solution (3:2). The solutions were mixed and immediately cooled to 20 °C.

In one of the flasks poured 1 cmof solution dimethylglyoxime in the other flask pour 1 cmof ethanol. The solutions were topped up to the mark with water and mix thoroughly. Within 25 minutes measure the optical density of colored solution with spectrophotometer at a wavelength of 530 nm or photoelectrocolorimeter with a filter having maximum transmission in the wavelength range of 530−550 nm. The thickness of the light absorbing layer of the cell is chosen so to obtain an optimal absorption of light, the optimal value of optical density.

As a solution comparison, using aliquot part of the analysis of a solution containing all reagents except dimethylglyoxime.

Simultaneously with the execution of the analysis carried out control experience for contamination of reagents.

From the values of absorbance of each test solution subtract the mean value of optical density in the reference experiment.

The weight of the Nickel find at calibration

graphics.

2.1.4. Construction of calibration curve

For steels with a mass fraction of from 0.01 to 0.05% Nickel in six sample beakers with a capacity of 200−250 cmis placed 0.5 g carbonyl iron or 0.5 g of steel, similar in composition to analyze, not containing Nickel, and poured sequentially 0,5; 1,0; 2,0; 3,0; 4,0 and 5,0 cmstandard solution of Nickel and further analysis is carried out as specified in clause 2.1.3.

For steels with a mass fraction of from 0.05 to 0.5% of Nickel in five glasses with a capacity of 200−250 cmis placed 0.5 g carbonyl iron or 0.5 g of steel, similar in composition to analyze, not containing Nickel, and pour consistently 5,0; 10,0; 15,0; 20,0; 25,0 cmstandard solution of Nickel and further analysis is carried out as specified in clause 2.1.3.

The found values of optical density and corresponding weight values of Nickel to build a calibration curve.

2.1.2−2.1.4. (Changed edition, Rev. No. 1).

2.2. The determination of Nickel (0,1−4,0%) in the steels with a mass fraction of copper to 2%, cobalt up to 1.5% manganese up to 2%

2.2.1. The essence of the method

The method is based on the formation of red color complex compounds of Nickel with dimethylglyoxime in an alkaline medium in the presence of oxidizing agent ammonium naternicola and measuring the light absorption of the solution at a wavelength of 440 nm.

2.2.2. Equipment and reagents

Spectrophotometer or photoelectrocolorimeter.

Potassium-sodium vinocity (4-water) according to GOST 5845−79, a solution of 200 g/DM.

Sodium hydroxide according to GOST 4328−77, a solution of 50 g/DM.

Neccersarily ammonium (ammonium persulfate) according to GOST 20478−75, a solution of 100 g/DM.

Dimethylglyoxime according to GOST 5828−77, a solution of 10 g/DMin the solution is 50 g/DMof hydrate of sodium oxide: 10 g dimethylglyoxime dissolved in 500 cmof a solution of 50 g/DMof hydrate of sodium oxide. The resulting solution was diluted to 1 DMwith a solution of 50 g/lhydrate sodium oxides; before use, the solution was filtered.

The other reagents and solutions for section 2.1

.2.

2.2.3. Analysis

A sample weighing 0.1 g was placed in a beaker with a capacity of 250−300 cm, dissolved by heating in 30 cmof sulphuric acid (1:5) and oxidize with nitric acid, adding it drop by drop. If the steel does not dissolve in sulphuric acid (1:5), the sample is dissolved in 30 cmof a mixture of acids. The solution was boiled to remove oxides of nitrogen, cooled, transferred to a volumetric flask with a capacity of 100 cmwhen the mass fraction of Nickel from 0.1 to 1.5%, or volumetric flask with a capacity of 200 cmwhen the mass fraction of Nickel, over 1.5% top up to the mark with water, mix and filter through a dry filter, discarding first portion of filtrate. Aliquote two parts of a solution at 10 cmis placed in a volumetric flask with a capacity of 100 cm, 20−30 cm, addwater and 2−3 drops of nitric acid. Next, with constant stirring, into each flask pour 10 cmof a solution of Rochelle salt, 20 cmof a solution of hydrate of sodium oxide and 10 cmnaternicola ammonium. After 0.5−1 min in one of the flasks poured 10 cmof the solution dimethylglyoxime in the other flask pour 10 cmof hydrate of sodium oxide and leave for 2−3 min.

The solutions were cooled, made up to the mark with water and mix. After 5 min measure the optical density of colored solution with spectrophotometer at a wavelength of 440 nm or photoelectrocolorimeter with a filter having maximum transmission in the wavelength range of 420−460 nm. The thickness of the light absorbing layer of the cell is chosen so to obtain an optimal absorption of light, the optimal value of optical density.

A solution of comparison, using the appropriate aliquot part of the analysis of a solution containing all reagents except dimethylglyoxime.

Simultaneously with the execution of the analysis carried out control experience for contamination of reagents.

From the values of absorbance of each test solution subtract the mean value of optical density in the reference experiment.

The weight of the Nickel find at calibration g

Rafik.

2.2.4. Six glasses with a capacity of 200−250 cmis placed 0.1 g carbonyl-iron or steel, similar in composition to the analyzed and does not contain Nickel. In five glasses poured consistently 1,0; 5,0; 10,0; 15,0; 20,0 cmstandard solution of Nickel and further analysis is carried out as specified in clause 2.2.3.

As a solution comparison, using a solution of iron or steel, in the sixth glass, which introduced all the reagents except the standard solution of Nickel.

On the found optical density and corresponding mass of Nickel to build a calibration curve.

2.3. Processing of the results

Mass fraction of Nickel () in percent is calculated by the formula

;

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

 — the weight of the portion corresponding to aliquote part of the solution,

2.2.2−2.3. (Changed edition, Rev. No. 1).

3. GRAVIMETRIC METHOD FOR THE DETERMINATION OF NICKEL

3.1. The essence of the method

The method is based on the deposition of Nickel in an alcoholic solution dimethylglyoxime in kabooming environment, drying the resulting precipitate of Nickel dimethylglyoximate at (120±5)°C and weighing.

3.2. Reagents

Hydrochloric acid by the GOST 3118−77 or GOST 14261−77 and diluted 1:1, 1:4, 1:10, 1:1000.

Nitric acid GOST 4461−77 or GOST 11125−84.

Hydrofluoric acid according to GOST 10484−78.

Sulfuric acid GOST 4204−77 or GOST 14262−78 and diluted 1:1, 1:4.

Tartaric acid according to GOST 5817−77, a solution of 500 g/DM.

Ammonia water according to GOST 3760−79.

Ammonium chloride according to GOST 3773−72, saturated solution.

Ammonium neccersarily according to GOST 20478−75, a solution of 200 g/DM.

Ammonium radamisty according to GOST 19522−74, a solution of 50 g/DM.

Sodium hydroxide according to GOST 4328−77, a solution of 50 g/DM.

Dimethylglyoxime according to GOST 5828−77, ethanol a solution of 10 g/DMof 10 g dimethylglyoxime was dissolved in ethanol in a volumetric flask with a capacity of 1 DM, made up to the mark with ethanol and mix; before use, the solution was filtered.

10 cmsolution is sufficient to precipitate 0.025 g of Nickel.

Ethyl alcohol GOST 18300−87 and diluted 1:3.

The thioacetamide solution of 20 g/DM.

Potassium preservatory ACCORDING to GOST 7172−76.

Universal indicator paper.

(Changed edition, Rev. No. 1

).

3.3. Analysis

3.3.1. The weight of steel depending on the Nickel content determined according to table 2.

Table 2*

___________________
*Table. 1. (Deleted, Rev. No. 1).

3.3.2. The determination of Nickel in steels with a mass fraction to 0.50% copper and containing cobalt and tungsten

The sample is placed in a steel Cup with a capacity of 400 cmand dissolved by heating in 25−30 cmof hydrochloric acid, oxidize 5−7 cmof nitric acid, adding it dropwise, and the solution evaporated to dryness. To the dry residue poured 10 cmof hydrochloric acid (1:1), evaporated to dryness and kept for at least 1 h at 130 °C.

3.3.2.1. After cooling to the dry residue add 10 cmof hydrochloric acid (1:1), heated to dissolve the salts, add 100−150 cmof hot water, heated to boiling and immediately filtered through the filter «white ribbon». The filter with the precipitate three times washed with hot hydrochloric acid (1:10) and then with hot hydrochloric acid (1:1000) to remove iron ions (control is carried out by reaction with ammonium radamisty). The primary filtrate is stored for the further course of the analysis.

The filter with precipitate was placed in a platinum crucible, dried, incinerated and burned. To the residue in the crucible add 2−5 cmhydrofluoric acid and 0.5 cmof sulphuric acid (1:1), evaporated to remove sulphuric acid fumes, the residue fused with 2−3 g of potassium peacemaking. The melt is leached with hot water in a glass, add 5 cmof hydrochloric acid (1:1) and the solution was filtered through a filter «white ribbon». Precipitate was washed 2−3 times with warm water. The filter is discarded, the filtrate is attached to the main filtrate.

3.3.2.2. To the combined filtrate add 40 cmof a solution of tartaric acid and ammonia to pH 8−9 (hereafter pH control lead to the universal indicator). The solution is diluted with water to a volume of 400 cm, acidified with hydrochloric acid (1:4) to pH 4−6, is heated to 50 °C, add 25−30 cmsolution dimethylglyoxime and with constant stirring, ammonia to pH 8−9. After settling, the precipitate check the completeness of precipitation of Nickel by adding a solution dimethylglyoxime. Solution and the precipitate was allowed to stand for at least 1 h at 40−60°C. Then the precipitate was filtered off on filter «white ribbon» and washed with hot water to remove iron ions. The filter cake is dissolved in hot hydrochloric acid (1:1), the filter washed with hot water. The solution is diluted with water to a volume of 400 cmand repeat the precipitation of Nickel by adding 5−15 cmof a solution of tartaric acid, 10−25 cmdimethylglyoxime solution and ammonia to pH 8−9. Solution and the precipitate was allowed to stand for 1 h at 40−60°C. the Residue is filtered over dried at (120±5) °C to constant weight and weighed glass filter crucible No. 3, washed with warm water and 3−4 times with ethanol (1:3).

The crucible with the precipitate is dried in a drying Cabinet, LRI a temperature of (120±5) °C to constant weight, cooled in a desiccator and weighed.

3.3.3. The determination of Nickel in steels containing cobalt with a mass fraction of copper to 0.50% and do not contain tungsten

A sample of steel is dissolved in 25−50 cmof hydrochloric acid and the combined filtrate determination is carried out according to item 3.3.2.

3.3.3.1. To the combined filtrate add 20−25 cmof a saturated solution of ammonium chloride, 20−40 cmof a solution of tartaric acid, ammonia to pH 9−10 and then add 5 cmof ammonia in excess. The solution is poured 20 cmof a solution of ammonium naternicola, boiled for 10−12 min, after cooling, is diluted with water to a volume of 400 cm, and was added hydrochloric acid (1.4) to a pH of 4−6.

The solution is heated to 50 °C, poured 25−50 cmsolution dimethylglyoxime and with constant stirring a solution of ammonia to pH 8−9. After the cessation of sediment adds another 30−40 cmof the solution dimethylglyoxime for the formation of a soluble salt of cobalt glyoxylate. Solution and the precipitate was allowed to stand at 40−60 °C for 1 h. the Precipitate was filtered off, the filter «white ribbon» and washed 5−6 times with warm water to remove iron ions. The precipitate is dissolved on the filter with a solution of hot hydrochloric acid (1:1), the filter was washed 5−7 times in hot water, collecting the filtrate in a beaker, in which was conducted the deposition. The solution is poured 10−20 cmof a saturated solution of ammonium chloride, 5 cmof tartaric acid, ammonia solution to pH 9−10, dilute with water to 350−400 cmand pour hydrochloric acid (1:4) to pH 4−6. The solution is heated to 50 °C, poured 25−30 cmsolution dimethylglyoxime and with constant stirring a solution of ammonia to pH 8−9. After the cessation of precipitation, add 10−20 cmsolution dimethylglyoxime. Solution and the precipitate was allowed to stand at 40−60 °C for 1 h. the Precipitate is filtered through dried at (120±5) °C to constant weight and weighed glass filter crucible No. 3, washed with warm water and 3−4% ethyl alcohol (1.3). The crucible with the precipitate is dried in a drying oven at (120±5) °C to constant weight, cooled in a desiccator and vzves

ivaut.

3.3.4. The determination of Nickel in steels containing tungsten, with a mass fraction of copper to 0.50% and do not contain cobalt

The sample is placed in a steel Cup with a capacity of 400 cm, was dissolved with heating in 30 cmof hydrochloric acid and oxidize 5−7 cmof nitric acid, adding it drop by drop.

Solution and the precipitate is heated to 50 °C, after 5 min, dilute with hot water up to 200−300 cm, boiled and filtered through filter «blue ribbon». Precipitate was washed 5−7 times with hot hydrochloric acid (1:10). The filtrate (main) retain.

The precipitate tungsten acid on the filter is dissolved in 50 cmhot solution of hydrate of sodium oxide and the filter was washed 5−7 times in hot water. The solution is discarded.

The filter was washed 5−7 times with hot hydrochloric acid (1:1), adding the washings to the main filtrate. The filter is discarded.

The resulting solution was evaporated to dryness, the residue moistened with hydrochloric acid, evaporated to dryness and kept for at least 1 h at 130 °C, further analysis is carried out as specified in clause 3.3.2.1.

3.3.5. Determination of Nickel in steels with a mass fraction of copper over 0.50% and do not contain cobalt and tungsten

The sample is placed in a steel Cup with a capacity of 400−500 cmand dissolved by heating in 30 cmof hydrochloric acid, oxidize 5−7 cmof nitric acid, adding it drop by drop. The solution was poured 30 cmof sulphuric acid (1:4) and evaporated to sulphuric acid fumes. The solution was cooled, diluted with water to a volume of 150−200 cm, a flow of 30−40 cmof a solution of thioacetamide and boil until complete coagulation of the precipitate. After 5−10 min the precipitate was filtered off, the filter «white ribbon» and washed 7−8 times with hot water. To the filtrate poured 5 cmnaternicola ammonium is boiled until the decomposition of thioacetamide and excess naternicola ammonium. The solution was filtered through a filter «white ribbon» and further analysis is carried out as specified in clause 3.3.2.2

.

3.3.6. The determination of Nickel in steels containing tungsten, copper and cobalt

The sample is placed in a steel Cup with a capacity of 400 cmand dissolved by heating in 30 cmof hydrochloric acid, oxidize 5−7 cmof nitric acid, adding it drop by drop. Solution and the precipitate is heated to 50 °C, after 5 min, dilute with hot water up to 200−300 cm, boiled and filtered through filter «blue ribbon». Precipitate was washed 5−7 times with hot hydrochloric acid (1:10). The filtrate was evaporated to dryness. The residue is moistened with hydrochloric acid, evaporated to dryness and kept for at least 1 h at 130 °C. After cooling to the dry residue add 10 cmof hydrochloric acid (1:1) and to the combined filtrate determination is carried out according to item 3.3.2. To the combined filtrate add 30 cmof sulphuric acid (1:4) and evaporated to the appearance of sulphuric acid fumes, further analysis is carried out according to clause 3.3.5 to decomposition of thioacetamide and excess naternicola ammonium. The solution was filtered through a filter «white ribbon», washed 4−6 times with hot water, add 20−30 cmof hydrochloric acid and complete analyses according to claim 3.3.3.1

.

3.4. Processing of the results

Mass fraction of Nickel in percent is calculated by the formula

where is the mass of sediment dimethylglyoximate of Nickel in the sample, g;

 — the mass of sediment dimethylglyoximate Nickel in a control experiment, g;

the weight of steel, g;

0,2032 — the conversion factor from dimethylglyoximate of Nickel on Nickel.

4. ATOMIC ABSORPTION METHOD FOR THE DETERMINATION OF NICKEL

4.1. The essence of the method

The method is based on measuring absorption of resonance radiation by free atoms of Nickel formed as a result of spraying the test solution in a flame air-acetylene.

4.2. Equipment and reagents

Atomic absorption spectrophotometer fiery.

Lamp with hollow cathode for the determination of Nickel.

The cylinder with acetylene.

The compressor that supplies compressed air or compressed air.

Hydrochloric acid by the GOST 3118−77 or GOST 14261−77.

Nitric acid GOST 4461−77 or GOST 11125−84.

Nickel metal according to GOST 849−97.

Standard solutions of Nickel.

Solution A. 0.5 g of metallic Nickel dissolved in 10 cmsalt and 10 cmof nitric acid. The solution was transferred to a volumetric flask with a capacity of 1 DM, cooled, made up to the mark with water and mix.

1 cmof the solution contains 0.0005 g of Nickel.

Solution B. 20 cmstandard solution And placed in a volumetric flask with a capacity of 100 cm, made up to the mark with water and stirred; prepared on the day of application.

1 cmof a solution contains 0.0001 g of Nickel.

(Changed edition, Rev. No. 1)

.

4.3. Preparation of the device

The training device is carried out in accordance with the attached instructions.

Set the spectrophotometer at a resonance line 232 nm or 341,5 nm depending on the Nickel content in the steel (tab. 3). After turning on gas supply and ignition of the burner spray water into the flame and set the instrument zero.

4.4. Analysis

4.4.1. The weight of steel depending on the Nickel content determined by the table. 3.

Table 3

The sample is placed in a steel Cup with a capacity of 100−150 cmand dissolved by heating in 10 cmof hydrochloric and 5−7 cmof nitric acid. The solution was evaporated to dryness. The dry residue is dissolved in 3−5 cmof hydrochloric acid, transferred to a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix. Part of the solution filtered through a dry filter «white ribbon» into the conical flask, discarding the first two portions of the filtrate.

When the mass fraction of Nickel in steel exceeding 1% aliquot part of the solution 10 cmis placed in a volumetric flask with a capacity of 100 cm, add 3−5 cmof hydrochloric acid, made up to the mark with water and mix.

Allowed another dilution of solutions so that the final concentration of Nickel was in the range corresponding to the straight-line segment calibration curve.

Is sprayed into the flame of the solution in the reference experiment, and then test solutions in order of increasing Nickel concentration to obtain stable readings for each solution. Prior to introduction into the flame each of the analyzed solution is sprayed water to wash the system and check the zero point.

From the average value of absorbance of each of the test solutions, the average value is subtracted absorption in the reference experiment. The Nickel content is found by calibration curve

.

4.4.2. The construction of a graded graph when the mass fraction of Nickel in the steel is between 0.10 to 5.0%

In six volumetric flasks with a capacity of 100 cmpour 3−5 cmof hydrochloric acid. Five flasks poured consistently 2,0; 4,0; 6,0; 8,0 and 10,0 cmstandard solution B of Nickel. Sixth bulb is used for the reference experiment. The solutions were topped up to the mark with water, mix and measure the intensity of absorption at a wavelength of 232 nm. The solutions were sprayed into the flame in order of increasing Nickel concentration, starting from the reference experiment. Prior to introduction into the flame each of the analyzed solution is sprayed water.

From the average value of absorbance of each test solution subtract the average value of the absorption in the reference experiment. On the found values of absorbance of solutions and the respective masses of Nickel to build a calibration curve.

4.4.3. Construction of calibration curve for the mass concentration of Nickel in steel from 5.0 to 15.0%

In six volumetric flasks with a capacity of 100 cmpour 3−5 cmof hydrochloric acid. Five flasks sequentially poured 1,0; 1,5; 2,0; 2,5 and 3,0 cmstandard solution And Nickel. Sixth bulb is used for the reference experiment. The solutions were topped up to the mark with water, mix and measure the intensity of absorption at a wavelength of 341,5 nm. The solutions were sprayed into the flame in order of increasing Nickel concentration, starting from the reference experiment. Prior to introduction into the flame each of the analyzed solution is sprayed water.

From the average value of absorbance of each test solution subtract the average value of the absorption in the reference experiment. On the found values of absorbance of solutions and the respective masses of Nickel to build a calibration curve.

4.4.2, 4.4.3. (Changed edition, Rev. No. 1).

4.5. Processing of the results

4.5.1. Mass fraction of Nickel in percent is calculated by the formula

where is the mass of Nickel in sample solution, found by calibration schedule g;

the weight of steel, suitable aliquote part of the solution,

(Changed edition, Rev. No. 1).

4.5.2. Allowable absolute discrepancies in the results of parallel measurements at a confidence level = 0.95 does not exceed the values specified in table. 4.

Table 4