GOST 22536.6-88

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  ГОСТ 22536.6-88

GOST 22536.6−88 carbon Steel and unalloyed cast iron. Methods for determination of arsenic

GOST 22536.6−88

Group B09

STATE STANDARD OF THE USSR

CARBON STEEL AND UNALLOYED CAST IRON

Methods for determination of arsenic

Carbon steel and unalloyed cast iron.
Methods for determination of arsenic

AXTU 0809

Valid from 01.01.90
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 ferrous metallurgy of the USSR

PERFORMERS

D. K. Nesterov, PhD. tech. Sciences; S. I. Rudyuk, PhD. tech. Sciences; S. V. Spirina, PhD. chem. Sciences. (supervisor); V. F. Kovalenko, PhD. tech. science; N. N. Gritsenko, PhD. chem. Sciences; L. I. birch; O. M. Kirzhner

2. APPROVED AND put INTO EFFECT by decision of the USSR State Committee for standards from 25.08.88 No. 3018

3. REPLACE GOST 22536.6−77

4. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

This standard specifies the photometric (with a mass fraction of arsenic from 0.01 to 0.20%) and potentiometric (when the mass fraction of arsenic from 0.02 to 0.20%) methods for determination of arsenic.

1. GENERAL REQUIREMENTS

1.1. General requirements for methods of analysis GOST 22536.0−87.

1.2. The error analysis results (at p = 0.95) does not exceed the limit given in table.1, when the conditions are met:

the discrepancy between the results of two (three) parallel dimensions should not exceed (with a confidence probability =0,95) of the values given in table.1;

played in the standard sample, the value of the mass fraction of arsenic should vary from certified more than acceptable (at a confidence level =0,85) the value given in table.1.

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) values are given in table.1.

Table 1

2. THE PHOTOMETRIC METHOD FOR THE DETERMINATION OF ARSENIC

2.1. The essence of the method

The method is based on formation of blue arsenic and molybdenum complex, the interaction of arsenic (a) with ammonium molybdate in the presence of the reducing agent is hydrazine sulfate. Arsenic is pre-separated from accompanying elements by Stripping in the form of arsenic trichloride or by precipitation with thioacetamide as a sulfide.

2.2. Equipment and reagents

Spectrophotometer or photoelectrocolorimeter.

Apparatus for distillation of arsenic GOST 14204−69 or other design.

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

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

Sulfuric acid GOST 4204−77, diluted 1:1, 1:4, and the solution with molar concentration of equivalent to 6 mol/DM.

Ammonia water according to GOST 3760−79 or GOST 24147−80.

Perchloric acid, h. e. a. or H. h

A mixture of hydrochloric and nitric acids (3:1) freshly prepared: to 150 cmof hydrochloric acid pour 50 cmof nitric acid and stirred.

Potassium bromide according to GOST 4160−74.

Sodium hydroxide according to GOST 4328−77, a solution with a mass concentration of 50 g/DMand 400 g/DM.

Phenolphthalein, alcohol solution with a mass concentration of 10 g/DM.

Hydrazine sulfate according to GOST 5841−74, a solution with a mass concentration of 1.5 g/DM.

Ammonium molybdate according to GOST 3765−78, recrystallized from alcohol, the solution with a mass concentration of 10 g/lin sulfuric acid solution with molar concentration of equivalent to 6 mol/DM. The solution is stable for 2 months.

Rectified ethyl alcohol according to GOST 5962−67 or GOST 18300−87.

Recrystallization of ammonium molybdate in 250 g of ammonium molybdate was dissolved in 400 cmof water at 70−80 °C. the Hot solution is filtered through filter «blue ribbon» in a glass contains 300 cmof ethyl alcohol. The solution was cooled and allowed to stand in running water for 1 h. Precipitated crystals are filtered off on a Buchner funnel with filter «white ribbon». The crystals are washed 2−3 times with ethanol in batches of 20−30 cmand dried in air.

Molybdate-hydrazine solution (reaction mixture): in a volumetric flask with a capacity of 1 DMis placed 100 cmof ammonium molybdate solution, dilute with water to 900 cm, add 10 cmof hydrazine sulfate solution, made up to the mark with water and mix.

Prepared immediately before use.

Potassium permanganate according to GOST 20490−75, a solution with a mass concentration of 1 g/DM.

Universal indicator paper pH.

Xylene according to GOST 9949−76.

Ascorbic acid, a solution with a mass concentration of 5 g/DM.

Tartaric acid according to GOST 5817−77, a solution with a mass concentration of 50 g/DM.

The thioacetamide, recrystallized from xylene, a solution with a mass concentration of 20 g/DM.

Recrystallization of thioacetamide: 30 g of thioacetamide dissolved in 100 cmof xylene at 85−90 °C with stirring. The upper layer of solution carefully decanted into a dry beaker with a capacity of 600−800см. In the glass with the remainder added to 100 cmof xylene, and dissolve again at 85−90 °C. the Top layer is poured into the same beaker with a capacity of 600−800 cm. This operation is repeated 3−4 times. The resulting solution was cooled in running water. Precipitated crystals of the thioacetamide was filtered on a Buchner funnel with two filter «white ribbon». The crystals are washed 2−3 times with xylene and dried in air.

The copper nitrate solution with a mass concentration of 10 g/DM.

Hydroxylamine hydrochloride according to GOST 5456−79.

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

Radio engineering carbonyl iron according to GOST 13610−79.

Arsenious anhydride according to GOST 1973−77.

Sodium mistakemistake ortho.

Standard solutions of arsenic.

Solution a: 0,1320 g trioxide arsenic dissolved in 5 cmof sodium hydroxide solution (50 g/DM), add 30 cmof water and sulfuric acid (1:1) until neutral reaction on indicator paper. Transfer the solution into a volumetric flask with a capacity of 1 DM, made up to the mark with water and mix.

Allowed the preparation of a standard solution of sodium michalowskiego ortho: 0,2601 michalowskiego g of sodium is dissolved in water in a volumetric flask with a capacity of 1 DM, made up to the mark with water and mix.

1 cmstandard solution contains 0.0001 g of arsenic.

Solution B: 10 cmstandard solution And placed in a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.

1 cmstandard solution B has the 0.00001 g of arsenic.

Solution B is prepared immedi

Redstone before use.

2.3. Analysis

2.3.1. The weight of steel or cast iron depending on the mass fraction of arsenic (see table.2) is placed in a beaker or conical flask with a capacity of 250−300 cm, cover with a watch glass and dissolved in 10 cmof a mixture of hydrochloric and nitric acids (3:1) with moderate heating.

Table 2

2.3.2. Preliminary separation of arsenic transport in the form of chloride.

After dissolution of the sample hour glass is washed with a small amount of water is added to the solution and 10 cmof sulphuric acid (1:1) and evaporated to start the selection of sulfuric acid vapor. The contents of the beaker or flask is cooled, carefully add 30 cmof hydrochloric acid (1:1) and quantitatively transferred into a flask for distillation with a capacity of 250 cm, together with undissolved salts, wall washing Cup 15 cmof water. The flask is added 0.5 g of hydrazine sulfate, 0.5 g of potassium bromide and slowly distilled arsenic trichloride, heating the solution not higher than 120 °C. Stripping was continued until until the receiver can not pass the 2/3 of the initial volume of the solution. The distillate is collected in a beaker with a capacity of 100 cm, which is pre-put 10 cmof water. The distillate is transferred to a volumetric flask with a capacity of 100 cm, adjusted to the mark with water and mix. Select 20 cmof the solution was placed in a beaker with a capacity of 100 cm, flow 10 cmof nitric acid, the solution was evaporated to dryness and the dry residue is kept for 40−60 min at 120−130 °C. After cooling, the contents of the glass poured 20 cmmolybdate-hydrazine solution. The glass is covered with glass and placed in a boiling water bath for 10 min. the Solution was cooled to 20 °C, poured into a volumetric flask with a capacity of 50 cm, made up to the mark the same molybdate-hydrazinium solution and stirred.

The optical density of the solutions measured after 30 min in the spectrophotometer at a wavelength of 840 nm or photoelectrocolorimeter with a filter having maximum transmission in the wavelength range of 650−710 nm or 710−900 nm. As a solution comparison, use water. Simultaneously with the execution of the analysis carried out control experience for contamination of reagents.

Oxidation of arsenic can be carried out with potassium permanganate. For this purpose the distillate is transferred into a measuring flask with a capacity of 100 cm, add two drops of phenolphthalein and neutralize with sodium hydroxide solution with the mass concentration of 400 g/DMuntil a steady crimson colors. Then poured dropwise sulfuric acid (1:4) to the disappearance of the colouring and three 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 cmof water 5 cmof a solution of ammonium molybdate in sulfuric acid, 2cmof a solution of ascorbic acid or a solution of hydrazine. 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 measured as described above. From the values of absorbance of the analyzed solution is subtracted the value of the optical density of the solution in the reference experiment.

The mass of arsenic found at a calibration chart or by comparison with a standard sample similar in composition to the sample and carried through all St

adiya analysis.

2.3.3. A preliminary separation of the arsenic by precipitation as a sulfide.

After dissolution of the sample hour glass is washed with a small amount of water, poured 20 cmof sulphuric acid (1:1) and evaporated to start the selection of sulfuric acid vapor. The contents of the beaker or flask is cooled, add 40−50 cmof water, dissolved salts when heated, pour 10 cmof a solution of tartaric acid and heated for 5−10 min. Then pour the ammonia to pH 8−9 by indicator paper, and heated for 15−20 min at 90−95 °C until complete dissolution of the precipitate. After cooling, to the solution was added sulfuric acid (1:1), to a pH of 2 on the indicator paper and 10 cmin excess, top up the solution with water to 180 cmand heated to boiling. Carefully add 2−5 g of hydroxylamine hydrochloride, and boil the solution until complete reduction of iron (by the reaction with ammonium radamisty). Add 10 cmof a solution of thioacetamide, 1 cmof solution of nitrate of copper, kept the solution from precipitated sediment sulphides in 10−15 minutes on a warm plate, then add another 10 cmof a solution of thioacetamide incubated 30−40 min at 85−90 °C and cooled.

After 4 h, the precipitate filtered off sulphides on the two filters «white ribbon», washed 6−7 times with water, dissolve the sulphides in the filter in the 30−40 cmhot mixture of hydrochloric and nitric acids (1:1) in portions of 10 cmand washed the residue on the filter 3−4 times with hot water collecting the filtrate and washings in a beaker, in which was conducted the deposition. The filter is discarded.

The solution is evaporated to a volume of 80−90 cm, transferred to a volumetric flask with a capacity of 100 cm, adjusted to the mark with water and mix. Select aliquot part of the solution is 20 cmand placed in a beaker with a capacity of 100 cm, the solution is evaporated to a volume of 3−5 cm, add 2 cmof perchloric acid and evaporated until the appearance of fumes of perchloric acid. The glass solution was cooled, washed walls of glass with water and repeat the evaporation until the appearance of fumes of perchloric acid.

After cooling, the contents of the beaker add 20 cmmolybdate-hydrazine solution and further taken as given

in p.2.3.2.

2.3.4. Construction of calibration curve

Six glasses with a capacity of 100 cm(when the oxidation of arsenic with nitric acid) or in six volumetric flasks with a capacity of 50 cm(when the oxidation of arsenic with potassium permanganate or the analysis according to claim 2.3.3) is placed 1; 2; 3; 4; 5; 6 cmstandard solution B, which corresponds to: 0,00001; 0,00002; 0,00003; 0,00004; 0,00005; 0,00006 g of arsenic. The seventh Cup (or a measuring flask) to which is added all the reagents, except standard solution of arsenic is used for the reference experiment.

When carrying out the oxidation of arsenic with nitric acid in all the cups poured 10 cmof nitric acid, the solution was evaporated to dryness and the dry residue is kept for 40−60 min at 120−130 °C.

After cooling, the contents of the glass poured 20 cmmolybdate-hydrazine solution. The glass is covered with glass and placed in a boiling water bath for 10 min. the Solution was cooled to 20 °C, poured into a volumetric flask with a capacity of 50 cm, made up to the mark the same molybdate-hydrazinium solution and stirred.

When carrying out the oxidation of arsenic with potassium permanganate in each volumetric flask with a capacity of 50 cmadded dropwise a solution of potassium permanganate until a stable for 1 min coloring, pour water to a volume of 40 cm, 5 cmsolution of ammonium molybdate in sulfuric acid, 2cmof a solution of ascorbic acid or a solution of hydrazine, stirring the solution after addition of each reagent. The contents of the flask were stirred and heated in a boiling water bath for 15 min, cooled, made up to the mark with water and mix. The analysis according to claim 2.3.3 in all the cups pour 2 cmof perchloric acid and evaporated until the appearance of fumes of perchloric acid. The glass solution was cooled, poured walls of glass with water and repeat the evaporation until the appearance of fumes of perchloric acid. After cooling, the contents of the beaker add 20 cmmolybdate-hydrazine solution. The glass is covered with glass and placed in a boiling water bath for 10 min. the Solution was cooled to 20 °C, poured into a volumetric flask with a capacity of 50 cm, made up to the mark the same molybdate-hydrazinium solution and stirred.

Optical density of the solution is measured as given in claim 2.3.2.

On the found values of optical density and corresponding weight values of arsenic build the calibration graph. Allowed construction of calibration curve in the coordinates: the optical density is the mass fraction of m

isiaka.

2.4. Processing of the results

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

,

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

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

2.4.2. Norms of accuracy and norms control the accuracy of determining the mass fraction of arsenic are given in table.1.

2.4.3. The method used in the dispute in the assessment of quality carbon steel and unalloyed cast iron.

3. POTENTIOMETRIC METHOD FOR THE DETERMINATION OF ARSENIC

3.1. The essence of the method

The method is based on potentiometric titration of arsenic (III) solution of potassium polnovatogo to obtain the jump in the potential. Arsenic is pre-separated from accompanying elements by Stripping in the form of trichloride of arsenic from hydrochloric acid solution in the presence of potassium bromide and hydrazine sulfate.

3.2. Equipment and reagents

Apparatus for distillation of arsenic GOST 14204−69 or other design.

The setup for potentiometric titration:

a pair of electrodes: indicator-platinum and the reference electrode — calomel;

magnetic or mechanical stirrer;

the DC millivoltmeter or pH meter that clearly capture the potential jump at the end point.

If necessary, the instrument sequentially connecting a variable resistance, allows measurement of the full scale range of the device.

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

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

A mixture of hydrochloric and nitric acids (3:1), prepared before use.

Sulfuric acid according to GOST 4204−77.

Potassium bromide according to GOST 4160−74.

Hydrazine sulfate according to GOST 5841−74.

Potassium branovitsky according to GOST 4457−74, solution with molar concentration of equivalent of 0.01 mol/DM, is prepared as follows: 0,2783 g previously recrystallized from water solution and dried at 150−180 °C polnovatogo potassium is dissolved in 100−120 cmof water is poured into a measuring flask with a capacity of 1 DM, made up to the mark with water and mix. Allowed preparation of the solution of fiksanala. Mass concentration () of a solution of potassium Bromeliaceae, expressed in g of arsenic per 1 cmof the solution is 0,0003746. The mass concentration of a solution of potassium bromoperoxidase () check for sodium thiosulfate, arsenious anhydride, or the standard sample, similar in composition and mass fraction of arsenic to the sample.

3.3. Analysis

The weight of steel or cast iron weighing 3 g were placed in a glass or flask with a capacity of 600 cm, flow 60 cmof a mixture of hydrochloric and nitric acids and 25−30 cmof sulfuric acid. A glass or beaker cover watch glass, and conduct dissolution initially at room temperature, and then with moderate heating until complete dissolution of the sample.

Rinse watch glass with a little water and evaporate the solution prior to the allocation of sulphuric acid fumes. The contents of the Cup is cooled, carefully poured 100 cmof hydrochloric acid (1:1), and quantitatively transfer the solution into a flask for distillation with a capacity of 250 cm. With high content of graphite should be applied to the flask with a capacity of 500 cm, as distillation takes place foaming of the solution.

In a flask add 1 g of potassium bromide, 3 g of hydrazine sulfate and slowly distilled arsenic trichloride, heating the solution not higher than 120 °C.

The distillate is collected in a beaker with a capacity of 400 cm, which is pre-placed 40 cmof water. The Stripping is continued until until the receiver can not pass the 2/3 of the initial volume of the solution.

The glass of the distillate is placed in a device for potentiometric titration, lower the stirrer and the electrodes and including a stirrer, stirred solution for 0.5−1 min. Then, without switching off the stirrer, titrate the solution by adding drop by drop from microburette branovitsky potassium to obtain a jump in 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 Bromeliaceae solution potassium with molar concentration of equivalent of 0.01 mol/DM, expressed in g of arsenic per 1 cmof solution;

 — weight naves

I.

3.4.2. Norms of accuracy and norms control the accuracy of determining the mass fraction of arsenic are given in table.1.