GOST 2604.11-85

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  ГОСТ 2604.11-85

GOST 2604.11−85 Cast iron alloy. Methods for determination of arsenic (Change No. 1)

GOST 2604.11−85

Group B09

INTERSTATE STANDARD

ALLOY CAST IRON

Methods for determination of arsenic

Alloy cast iron. Methods for determination of arsenic

ISS 77.080.10
AXTU 0809

Date of introduction 1986−07−01

Resolution of the USSR State Committee for standards from April 22, 1985 No. 1130 date of introduction is established 01.07.86

Limitation of actions taken by Protocol No. 5−94 of the Interstate Council for standardization, Metrology and certification (ICS 11−12−94)

REPLACE GOST 2604.11−77

EDITION with Change No. 1, approved in July 1990 (IUS 11−90).


This standard specifies methods for the determination of arsenic in doped iron: photometric (with a mass fraction of from 0.01 to 0.25%); potentiometric (with a mass fraction of from 0.05 to 0.25%).

1. GENERAL REQUIREMENTS

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

1.2. The error analysis result (at p = 0.95) does not exceed the limit shown in the table, under the following conditions:

the discrepancy between the results of two (three) parallel dimensions should not exceed (at p = 0.95) of the values given in the table;

played in the standard sample, the value of the mass fraction of arsenic should vary from certified more than acceptable (at a confidence level of 0.85) the value given in the table.

If any of the above conditions, a second measurement of the mass fraction of arsenic. If in repeated measurements the precision requirement of the results are not met, the results of the analysis recognize the incorrect measurements cease to identify and eliminate the causes of violation of the normal course of analysis.

The divergence of the two middle results of an analysis performed under different conditions (for example, when the control intralaboratory reproducibility) shall not exceed (at p = 0.95) of the values given in the table.

(Added, Rev. N 1).

2. PHOTOMETRIC METHOD

2.1. The essence of the method

The method is based on formation of blue arsenic-molybdenum complex in the interaction of pentavalent arsenic with ammonium molybdate in the presence of a reducing agent — ascorbic acid or hydrazine sulphate. Arsenic is pre-separated from the accompanying elements of cast iron by distillation in the form of trichloride of arsenic from hydrochloric acid solution in the presence of potassium bromide and hydrazine sulfate.

2.2. Apparatus, reagents and solutions

Photoelectrocolorimeter or spectrophotometer.

Apparatus for distillation of arsenic GOST 14204−69.

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

Nitric acid GOST 4461−77.

A mixture of hydrochloric and nitric acids 3:1. Prepared immediately before use.

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

Potassium bromide according to GOST 4160−74 and a solution of 0.1 g/cm.

Hydrazine sulfate according to GOST 5841−74 and solutions of 0.05 and 0.0015 g/cm.

In the solution rehabilitation: a solution of hydrazine sulfate 0.05 g/cm, previously slightly warmed, mixed with a solution of potassium bromide in the ratio 2:1. Prepare immediately before use. Allowed the use of restorative mixture of dry reagents.

Sodium hydroxide according to GOST 4328−77, a solution of 0.4 g/cm.

Phenolphthalein indicator, alcoholic solution of 0.01 g/cm.

Rectified ethyl alcohol GOST 18300−87.

Potassium permanganate according to GOST 20490−75, a solution of 0.001 g/cm.

Ammonium molybdate according to GOST 3765−78.

Sernovodsky reagent.

12.5 g ammonium molybdate was dissolved with heating in 250 cmof water, filtered through a dense filter (blue ribbon). In a glass with a capacity of 1 DMpour 500 cmof water and slowly poured with stirring 190 cmsulfuric acid, cooled and gradually poured with stirring cooled solution of ammonium molybdate. The solution was transferred to a volumetric flask with a capacity of 1 DM, made up to the mark with water and mix. A solution of ammonium molybdate in sulphuric acid resistant 2 months.

Acid chloride with a density of 1.51 g/cm.

Chornobryvtsy reagent.

8.1 g of ammonium molybdate was dissolved with heating in 250 cmof water. In a glass with a capacity of 1 DMflow 300 cmof water, 350 cmof perchloric acid and mixed, then gradually under stirring to the obtained solution poured chilled solution of molybdate of ammonium. The solution was transferred to a volumetric flask with a capacity of 1 DM, made up to the mark with water and mix. A solution of ammonium molybdate in perchloric acid resistant 2 months.

Ascorbic acid, solution 0,005 g/cm.

The refined arsenious anhydride according to GOST 1973−77.

Sodium mistakemistake ortho (NaASO).

Standard solutions of arsenious anhydride or michalowskiego sodium ortho:

the solution And the mass concentration of arsenic of 0.1 mg/cm:

0,132 g of arsenious anhydride is dissolved in 5 cmof sodium hydroxide solution in a beaker with a capacity of 100 cm, neutralized with sulfuric acid solution of 1:4 by phenolphthalein and transferred to volumetric flask with a capacity of 1 DM, made up to the mark with water and mix.

Allowed the preparation of a standard solution And michalowskiego sodium ortho: 0,256 g michalowskiego sodium ortho dissolved in a volumetric flask with a capacity of 1 DMin the water, bring to the mark with water and mix;

solution B with a mass concentration of arsenic is 0.01 mg/cm:

10 cmstandard solution And placed in a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix; prepare before use.

Indicator paper is universal.

Carbonyl iron OS.h.

(Changed

I edition, Rev. N 1).

2.3. Analysis

2.3.1. Determination of arsenic chernomyirdin reagent

A portion of the cast iron mass of 1 g (in mass fraction of arsenic of 0.01−0.05%) and 0.2 g (for the mass concentration of arsenic higher than 0.05%) were placed in a glass or flask with a capacity of 250−300 cm, flow 20 cmof a mixture of hydrochloric and nitric acids and 20 cmsulphuric acid 1:1. Dissolve a portion with a moderate heat and evaporated to the start of allocation of steams of sulfuric acid. Cooled, poured 20 cmof hydrochloric acid and quantitatively with 25−30 cmof water transferred into the flask of distillation apparatus. Add 15 cmrecovery solution or 0.5 g of potassium bromide and 1 g of hydrazine sulfate and quickly connect the flask with a refrigerator. The Stripping of arsenic trichloride is carried out at moderate heating at a temperature not higher than 120 °C.

Device check for leaks by using universal indicator paper. This is distilled with hydrochloric acid of 1:2, checking the connection of the bulb with a refrigerator using strips of universal indicator paper placed on the outside at the junction of the cone. In case of leakage in sections of the device need to grind.

Allowed Stripping of arsenic trichloride in a current of nitrogen or other inert gas.

Distillate collected in a glass receiver (beaker) with a capacity of 100 cm, which is pre-poured 10 cmof water. Distilled not less than the initial volume of the solution. Distillate transferred to a volumetric flask with a capacity of 100 cm, add 2 drops of phenolphthalein and neutralize with sodium hydroxide solution until a steady crimson colors. Then added dropwise sulfuric acid 1:4 to the disappearance of the colouring and 3 drops in excess. The solution was cooled, made up to the mark with water and mix.

In a volumetric flask with a capacity of 50 cmis placed aliquot part of the solution is 20 cm, are added dropwise with stirring a solution of potassium permanganate until a stable for 1 min coloring. Pour 15 cmwater 4 cmTernopoloblenergo reagent and 2 cmof a solution of ascorbic acid or a solution of hydrazine 0.0015 g/cm. The contents of the flask were stirred and heated in a boiling water bath for 15 min.

The solution was cooled, made up to the mark with water and mix.

Optical density of the solution is measured on a photoelectrocolorimeter with a filter having a region of transmittance in the wavelength interval 600−700 nm, or spectrophotometer at a wavelength of 840 nm.

A solution of comparison used water.

Mass fraction of arsenic found by the calibration graph with amendments, the control

wow experience.

2.3.2. Construction of calibration curve

Six glasses with a capacity of 250−300 cmis placed sample of carbonyl iron with a mass of 1 g (in mass fraction of arsenic of 0.01−0.05%) or 0.2 g (for the mass concentration of arsenic higher than 0.05%).

In five glasses poured consistently 2; 4; 6; 8 and 10 cmstandard solution B, corresponding to the values of the mass fraction of arsenic 0,01; 0,02; 0,03; 0,04; 0,05% in relation to the initial suspension of 1 g or 0.05; 0,10; 0,15; 0,20 and 0,25% relative to the initial charge of 0.2 g the Sixth glass is used for the reference experiment. In every glass poured 20 cmof a mixture of hydrochloric and nitric acids and 20 cmsulphuric acid 1:1. Sample is dissolved with moderate heating. Then do as stated in claim 2.3.1. On the found values of optical density of the solutions (taking into account the result of the control experiment) and their corresponding values of mass fractions of arsenic build the calibration graph.

2.3.3. Determination of arsenic chlorotoluidines reagent — according to claim 2.3.1 with the following addition:

in a volumetric flask with a capacity of 50 cmis placed aliquot part of the solution is 20 cmand dropwise with stirring add a solution of potassium permanganate until a stable for 1 min coloring. Poured 20 cmchlorotoluidines reagent and 2 cmof a solution of ascorbic acid or hydrazine solution of 0.0015 g/DM. The contents of the flask were stirred and heated in a boiling water bath for 15 min.

The solution was cooled, made up to the mark with water and mix.

2.3.4. Construction of calibration curve in the determination of arsenic chlorotoluidines reagent — according to claim 2.3.2, with the following addition:

to each flask are added dropwise with stirring a solution of potassium permanganate until a stable for 1 min coloring. Poured 20 cmchlorotoluidines reagent and 2 cmof a solution of ascorbic acid or a solution of hydrazine 0.0015 g/cm. The solutions were heated in a boiling water bath for 15 min, then cooled, made up to the mark with water and mix.

2.3.1−2.3.4. (Changed edition, Rev. N 1).

2.4. Processing of the results

2.4.1. Mass fraction of arsenic, in percent find the calibration schedule.

2.4.2. Norms of accuracy and norms of control of accuracy of measuring the mass fraction of arsenic given in the table.

(Changed edition, Rev. N 1).

3. POTENTIOMETRIC METHOD

3.1. The essence of the method

The method is based on the oxidation of arsenic (III) to arsenic (V) in hydrochloric acid medium by a solution of potassium Bromeliaceae. The equivalence point is determined by the change in the potential of platinum electrode at the potential of a saturated calomel electrode or tungsten. Arsenic is pre-separated from related items by distillation in the form of arsenic trichloride in the presence of potassium bromide and hydrazine sulfate.

3.2. Apparatus, reagents and solutions

The setup for potentiometric titration.

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

Potassium branovitsky according to GOST 4457−74, solution with molar concentration of equivalent of 0.01 mol/DM: 0,2784 g previously recrystallized from water solution and dried at 150−180 °C polnovatogo potassium is dissolved in 100−120 cmof water, poured the solution into a volumetric flask with a capacity of 1 DM, made up to the mark with water and mix.

The mass concentration of a solution of potassium polnovatogo for arsenic () is set in the following manner: in a beaker with a capacity of 300 cmpour 10 cmof a standard solution And further analysis is carried out as specified in clause 3.3. Simultaneously titrated solution in the reference experiment.

The mass concentration of a solution of potassium bromoperoxidase () for arsenic in g/cmis calculated by the formula

,

where is the mass of arsenic in aliquotes part of standard solution, g;

the volume of the solution polnovatogo potassium consumed in the titration of a standard solution, cm;

the volume of the solution polnovatogo potassium consumed for titration of the solution in the reference experiment, cm.

The solution is allowed to prepare fiksanala, with =0,000375 g/cm.

The other reagents and solutions — p. 2.2.

(Changed edition, Rev. N 1)

.

3.3. Analysis

The weight of cast iron weighing 1 g is placed in a beaker with a capacity of 250−300 cmand further analysis is carried out as specified in clause 2.3.1.

Distillate collected in a glass receiver with a capacity of 250−300 cm, which is pre-filled with 30−40 cmof water, distilled not less than 2/3 of the initial volume of the solution.

A glass of distillate placed in a device for potentiometric titration, lower the stirrer and the electrodes, the stirrer is rotated and stirred solution for 0.5−1 min. Then, without switching off the stirrer, the solution was titrated by adding dropwise a solution of potassium bromoperoxidase from microburette to obtain the jump in the potential.

3.4. Processing of the results

3.4.1. Mass fraction of arsenic () in percent is calculated by the formula

,

where  — volume of the solution polnovatogo potassium, used for titration of the test solution, cm;

the volume of the solution polnovatogo potassium consumed for titration of the solution in the reference experiment, cm;

 — mass concentration of a solution of potassium polnovatogo of arsenic, g/cm;

the weight of cast iron, g

.

3.4.2. Norms of accuracy and norms of control of accuracy of measuring the mass fraction of arsenic given in the table.

3.4.1, 3.4.2. (Changed edition, Rev. N 1).