GOST 24018.6-80
GOST 24018.6−80 heat-resistant Alloys on a Nickel basis. Methods for determination of arsenic (with Amendments No. 1, 2)
GOST 24018.6−80
Group B39
INTERSTATE STANDARD
ALLOYS HIGH-TEMPERATURE NICKEL-BASED
Methods for determination of arsenic
Nickel-based fire-resistant alloys.
Methods for the determination of arsenic
ISS 77.120.40
AXTU 0809
Date of introduction 1981−07−01
INFORMATION DATA
1. DEVELOPED AND INTRODUCED by the Ministry of metallurgy of the USSR
2. APPROVED AND put INTO EFFECT by Decision of the USSR State Committee for standards from 28.02.80 N 958
3. INTRODUCED FOR THE FIRST TIME
4. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS
| |
|
The designation of the reference document referenced
|
The number of the paragraph, subparagraph
|
GOST 859−78
|
2.2, 3.2
|
GOST 1973−77
|
2.2, 3.2
|
GOST 3118−77
|
2.2, 3.2
|
GOST 3760−79
|
2.2, 3.2
|
GOST 3765−78
|
2.2
|
GOST 4160−74
|
2.2, 3.2
|
GOST 4204−77
|
2.2, 3.2
|
GOST 4328−77
|
2.2, 3.2
|
GOST 4461−77
|
2.2, 3.2
|
GOST 5456−79
|
2.2, 3.2
|
GOST 5817−77
|
2.2, 3.2
|
GOST 5841−74
|
2.2
|
GOST 5962−67
|
2.2
|
GOST 6552−80
|
2.2, 3.2
|
GOST 9722−79
|
2.2, 3.2 |
GOST 10157−79
|
3.2
|
GOST 11125−84
|
2.2, 3.2
|
GOST 13610−79
|
2.2, 3.2
|
GOST 14204−69
|
2.2, 3.2
|
GOST 14261−77
|
2.2, 3.2
|
GOST 14262−78
|
2.2, 3.2
|
GOST 18300−87
|
2.2
|
GOST 19522−74
|
2.2, 3.2
|
GOST 24018.0−90
|
1
|
GOST 24147−80
|
2.2
|
5. Limitation of actions taken by Protocol No. 7−95 Interstate Council for standardization, Metrology and certification (ICS 11−95)
6. EDITION (August 2004) with Changes No. 1, 2 approved in December 1985, December 1990 (IUS 4−86, 3−91)
This standard sets the photometric method for the determination of arsenic (in mass fractions of from 0.001% to 0,010%) and flameless atomic absorption method for the determination of arsenic (in mass fractions of from 0.0001% to 0.005%).
(Changed edition, Rev. N 1).
1. GENERAL REQUIREMENTS
General requirements for methods of analysis GOST 24018.0.
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-molybdenum complex in the interaction of pentavalent arsenic with ammonium molybdate in the presence of the reducing agent is hydrazine sulfate. Arsenic is pre-separated from the accompanying elements of the alloy Stripping in the form of trichloride of arsenic from hydrochloric acid solution in the presence of the reducing agent hydrazine sulfate and bromide of potassium or the first deposition of ammonia hydroxide of iron, then in the form of a sulfide by thioacetamide in sulfuric acid solution with molar concentration of equivalent to 0.5 mol/DM
, using as a collector of copper sulfide.
(Changed edition, Rev. N 1, 2).
2.2. Apparatus, reagents and solutions
Spectrophotometer or photoelectrocolorimeter.
Thermometer.
Apparatus for distillation of arsenic GOST 14204.
Hydrochloric acid according to GOST 3118, GOST 14261 and diluted 1:1.
Nitric acid according to GOST 4461, GOST 11125 and diluted 1:1.
Sulfuric acid according to GOST 4204, GOST 14262 and diluted 1:4, 1:1.
Perchloric acid, a solution with a mass concentration of 57 g/cm, (g/DM).
Orthophosphoric acid according to GOST 6552 and diluted 1:1.
A mixture of hydrochloric and nitric acids: the 150 cmof hydrochloric acid pour 50 cmof nitric acid and mix; dilute 1:1, prepared immediately before use.
Tartaric acid according to GOST 5817, a solution with a mass concentration of 50 g/cm, (g/DM).
Ammonia water according to GOST 3760, GOST 24147 and diluted 1:500.
Hydroxylamine hydrochloride according to GOST 5456.
Ammonium radamisty according to GOST 19522, solution with a mass concentration of 5 g/cm, (g/DM).
Potassium bromide according to GOST 4160.
Sodium hydroxide according to GOST 4328, a solution with a mass concentration of 5 g/cm, (g/DM).
The xylene.
Ethyl alcohol according to GOST 5962* or GOST 18300.
________________
* On the territory of the Russian Federation GOST R 51652−2000.
The thioacetamide, recrystallized from xylene, a solution with a mass concentration of 2 g/cm(g/DM).
Recrystallization of thioacetamide: 30 g of thioacetamide dissolved in 100 cmof xylene at a temperature of 85 °C — 95 °C with stirring. The upper layer of solution carefully decanted into a dry beaker with a capacity of 600−800 cm. In the glass with the remainder added to 100 cmof xylene, and dissolve again at a temperature of 85 °C — 90 °C. the Upper layer of a solution of thioacetamide poured into the same beaker with a capacity of 600−800 cm. This operation is repeated 4−5 times. The remainder of the cast. The resulting solution was cooled in running water. Precipitated crystals of the thioacetamide was filtered on a Buchner funnel with two medium density filter (white ribbon). The crystals are washed 2−3 times with xylene, dried in air.
Ammonium molybdate according to GOST 3765, recrystallized from alcoholic solution.
Recrystallization of ammonium molybdate in 250 g of ammonium molybdate was dissolved in 400 cmof water at a temperature of 70 °C — 80 °C. the Hot solution is filtered through a dense filter into 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 a medium density filter (white ribbon), the crystals are washed 2−3 times with ethanol in batches of 20−30 cm, was dried in air.
Chornobryvtsy reagent: 5 g of ammonium molybdate dissolved in 100 cmwater when it is heated, cooled. Then in a glass with a capacity of 1 DMpour 500 cmof water, 230 cmof perchloric acid gradually with stirring enter 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; prepare immediately before use.
Hydrazine sulfate according to GOST 5841, solution with a mass concentration of 0.15 g/cm(g/DM).
Ascorbic acid, food, a solution with a mass concentration of 0.5 g/cm(g/DM).
Nickel powder according to GOST 9722*.
________________
* On the territory of the Russian Federation GOST 9722−97. Here and hereinafter. — Note the manufacturer’s database.
Copper grade М00бк according to GOST 859*.
________________
* On the territory of the Russian Federation GOST 859−2001. Here and hereinafter. — Note the manufacturer’s database.
The copper nitrate solution with a mass concentration of 1 g/cm(g/DM):
1 g of copper metal is dissolved by heating in 15−20 cmof nitric acid (1:1).
The solution was cooled, transferred to a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.
Carbonyl iron brand PS according to GOST 13610.
Iron sulfate, a solution with a mass concentration of 1 g/cm(g/DM):
1 g of carbonyl iron is dissolved in 30 cmof sulphuric acid (1:4) when heated. Then poured carefully dropwise nitric acid until the termination of foaming solution. The solution was boiled, cooled, transferred to a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.
Arsenious anhydride mark «refined» according to GOST 1973.
Sodium mistakemistake ortho (Na
AsO).
Standard solutions of arsenic.
Solution a: 0,132 g of arsenious anhydride is dissolved in 5 cmof sodium hydroxide solution with a mass concentration of 5 g/cm, (DM), dilute with water to 200 cm, and was added sulfuric acid (1:1) until neutral reaction on the universal indicator. The solution was transferred to 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. 0,256 g michalowskiego sodium ortho dissolved in 200 cmof water and then do as above in the preparation of a solution of arsenious anhydride.
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, is prepared immediately before use.
(Changed edition, Rev. N 1, 2).
2.3. Analysis
2.3.1. Determination of arsenic after prior separation by Stripping in the form of arsenic trichloride
The weight of the alloy: 1 g when the mass fraction of arsenic from 0.001% to 0.005% or 0.5 g when the mass fraction of arsenic in excess of 0.005% to 0,010% were placed in a glass (or flask) with a capacity of 250−300 cm, 30 cm, pour themixture of hydrochloric and nitric acid, cover the beaker (or flask) watch glass and dissolve a portion of the alloy when heated. To the solution was added 15 cmof perchloric acid, evaporated the solution to start the selection, vapor perchloric acid and heated for 15−20 min for the oxidation of chromium (III) to chromium (VI).
Salt is dissolved in 100−120 cmwater when it is heated, pour 3 cmof a solution of iron sulfate and pre-separates the ammonia arsenic with the ferric hydroxide by adding ammonia solution prior to the precipitation of ferric hydroxide and excess of it 10−15 cm. The contents of the beaker (or flask) and heated for 5−10 min to coagulate the precipitate. The precipitate was filtered off on a medium density filter (white ribbon), washed 5−7 times with a hot solution of ammonia (1:500). The precipitate is dissolved on the filter in the 30−40 cmhot mixture of hydrochloric and nitric acids (1:1) in portions of 10 cm. Washed the filter with hot water 3−4 times, the filter is discarded.
To the filtrate is poured 10 cmof sulphuric acid, 10 cmof phosphoric acid (1:1) and evaporated to start the selection of sulfuric acid vapor. Wash the walls of the beaker or flask with water and again evaporate the solution to start the selection of sulfuric acid vapor, is cooled. Carefully pour 5 cmof water and transfer the solution into the distillation flask, add 15 cmof hydrochloric acid, 0.5 g potassium bromide, 0.5 g of hydrazine sulphate and slowly heating the solution, distilled arsenic trichloride at a temperature not higher than 120 °C. the Distillate is collected in the beaker (or flask) capacity of 100 cm, which is pre-poured 10 cmof water. The Stripping is continued until until the receiver will not pass 
the initial volume of the solution.
To the distillate add 10 cmof nitric acid, evaporated the solution to dryness and the dry residue is heated for 40−60 min at 120 °C — 130 °C. After cooling, the contents of the beaker or flask and add 20 cmchlorotoluidines reagent, 1 cmof sulfuric acid solution of hydrazine or 1 cmof a solution of ascorbic acid, stirred and heated solution in a boiling water bath for 10−15 min. the Solution was cooled, transferred to a volumetric flask with a capacity of 50 cm, made up to the mark chlorotoluidines reagent, and mix. Simultaneously with the execution of the determination carried out control experience in which pre-add 3 cmof a solution of sulphate of iron.
Absorbance measured on the spectrophotometer at 
840 nm or photoelectrocolorimeter with a filter having a region of transmittance in the wavelength interval from 640 to 700 nm in a cuvette with a layer thickness of 20 mm. as a solution comparison, use water. The mass of arsenic found at the calibration schedule subject to amendments the reference experiment.
2.3.2. Determination of arsenic after preliminary separation of thioacetamide as a sulfide
The weight of the portion of the alloy is 1 g when the mass fraction of arsenic from 0.001% to 0.005% or 0.5 g when the mass fraction of arsenic in excess of 0.005% to 0,010% were placed in a glass (or flask) with a capacity of 250−300 cm, 30 cm, pour themixture of hydrochloric and nitric acids, cover beaker or flask with a watch glass and dissolve a portion of the alloy when heated.
To the solution was added 15 cmof perchloric acid, the solution evaporated to release vapors of perchloric acid and heated for 15−30 min for the oxidation of chromium (III) to chromium (VI).
Salt is dissolved in 100−120 cmwater when it is heated, pour 3 cmof a solution of iron sulfate and pre-separates the ammonia arsenic with the ferric hydroxide by adding ammonia solution prior to the precipitation of ferric hydroxide and excess of it 10−15 cm. Solution and the precipitate was heated for 5−10 min to coagulate the precipitate. The precipitate was filtered off on a medium density filter «white ribbon», washed 5−7 times with a hot solution of ammonia (1:500) and dissolved on the filter with 50 cmof hot sulphuric acid (1:4), in portions of 10−15 cm. The filter was washed 5−6 times with hot water and discarded.
To the filtrate is poured 10 cmof tartaric acid solution with a mass concentration of 50 g/cm, (DM), heat the solution for 10−15 min at 90 °C — 95 °C, cooled, poured ammonia solution to pH 8−9 by universal indicator solution and heated for 15−20 min at 90 °C — 95 °C until complete dissolution of the precipitate. The solution was poured sulfuric acid (1:1) to pH 2 by universal indicator and an excess of 10 cm, top up the solution with water to approximately 180 cmand heated to boiling. Carefully add 1−2 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 spot plate, add another 10 cmof a solution of thioacetamide, allowed to stand at a temperature of 85 °C — 90 °C for 30−40 min and cooled.
After 4 h, the precipitate filtered off sulphides in two medium density filter «white ribbon», washed 6−7 times with water, dissolve the sulphides in the 30−40 cmhot mixture of hydrochloric and nitric acids (1:1) in portions of 10 cm. The residue is washed on the filter with hot water 3−4 times, the filter is discarded. The solution was evaporated to a volume of 3−5 cm, add 1 cmof perchloric acid and evaporated to start the selection of the vapor of perchloric acid. Wash the side of the Cup with water and again evaporated to release vapors of perchloric acid. After that, the evaporation to fumes of perchloric acid was repeated once more.
Add 20 cmchlorotoluidines reagent, 1 cmof sulfuric acid solution of hydrazine or 1 cmof a solution of ascorbic acid, stirred and heated in a boiling water bath for 10−15 min. the Solution was cooled, transferred to a volumetric flask with a capacity of 50 cm, made up to the mark chlorotoluidines reagent, and mix. Simultaneously with the execution of the determination carried out control experience in which pre-add 3 cmof a solution of sulphate of iron.
Absorbance measured on the spectrophotometer at 
840 nm or photoelectrocolorimeter with a filter having a region of transmittance in the wavelength interval from 640 to 700 nm in a cuvette with a layer thickness of 20 mm. as a solution comparison, use water. The mass of arsenic found at the calibration schedule subject to amendments the reference experiment.
(Changed red
action, Rev. N 1, 2).
2.3.3. Construction of calibration curve
Six glasses or flasks with a capacity of 250−300 cmis placed 0.5 grams of Nickel powder. Five cups (or flasks) poured consistently 1,0; 2,0; 3,0; 4,0; 5,0 cmstandard solution B of arsenic.
The sixth beaker (or flask) used for carrying out control of the experience. In all the cups (or flasks) and add 3 cmof a solution of sulphate of iron and 30 cmof a mixture of hydrochloric and nitric acids and 10 cmof perchloric acid. The solutions were evaporated until the appearance of fumes of perchloric acid and then act as described in the claims.2.3.1 and 2.3.2.
From the values of optical density of analyzed solutions is subtracted the value of optical density in the reference experiment. The found values of optical density of the solutions and the corresponding mass of arsenic build the calibration graph.
(Changed edition, Rev. N 2).
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, was found in the calibration schedule g;
— the weight of the portion of alloy,
2.4.2. The absolute differences of the results of the parallel definitions should not exceed (at p = 0.95) of permissible values, specified in table.3.
(Changed edition, Rev. N 2).
3. FLAMELESS ATOMIC ABSORPTION METHOD FOR THE DETERMINATION OF ARSENIC
3.1. The essence of the method
The method is based on measurement of the absorption of radiation by free atoms of arsenic when 
of 193.7 nm, formed with the introduction of the analyzed solution into the graphite cuvette. Arsenic is pre-separated from the accompanying elements of the alloy Stripping in the form of trichloride of arsenic from hydrochloric acid solution in the presence of the reducing agent hydrazine sulfate and bromide of potassium or precipitation as a sulfide by thioacetamide in 1 mol/DMsulfuric acid solution, using as a collector of copper sulfide.
3.2. Apparatus, reagents and solutions
Atomic absorption spectrophotometer with electrothermal atomizer.
Lamp for determination of arsenic.
Thermometer.
Argon high purity according to GOST 10157 or a mixture of argon with 5% hydrogen.
Apparatus for distillation of arsenic GOST 14204.
Hydrochloric acid according to GOST 3118 or GOST 14261 and diluted 1:1.
Nitric acid according to GOST 4461 or GOST 11125 and diluted 1:1.
Sulfuric acid according to GOST 4204 or GOST 14262 and diluted 1:4, 1:1.
Perchloric acid, a solution with a mass concentration of 57 g/cm, (g/DM).
Orthophosphoric acid according to GOST 6552 and diluted 1:1.
A mixture of hydrochloric and nitric acids: the 150 cmof hydrochloric acid pour 50 cmof nitric acid and mix; dilute 1:1. The mixture of acids prepared immediately before use.
Tartaric acid according to GOST 5817, a solution with a mass concentration of 50 g/cm, (g/DM).
Ammonia water according to GOST 3760 and diluted 1:500.
Hydroxylamine hydrochloride according to GOST 5456.
Ammonium radamisty according to GOST 19522, solution with a mass concentration of 5 g/cm, (g/DM).
Potassium bromide according to GOST 4160.
Sodium hydroxide according to GOST 4328, a solution with a mass concentration of 5 g/cm, (g/DM).
The xylene.
The thioacetamide, recrystallized in xylene, a solution with a mass concentration of 2 g/cm(g/DM).
Recrystallization of thioacetamide: 30 g of thioacetamide dissolved in 100 cmof xylene at a temperature of 85 °C — 95 °C with stirring. The upper layer of solution carefully decanted into a dry beaker with a capacity of 600−800 cm. In the glass with the remainder added to 100 cmof xylene, and dissolve again at a temperature of 85 °C — 90 °C.
The top layer of a solution of thioacetamide poured into the same beaker with a capacity of 600−800 cm. This operation is repeated 4−5 times. The remainder of the cast. The resulting solution was cooled in running water. Precipitated crystals of the thioacetamide was filtered on a Buchner funnel with two medium density filter (white ribbon). The crystals are washed 2−3 times with xylene, dried in air.
Universal indicator paper pH 1−10.
Nickel powder according to GOST 9722.
Copper grade М00бк according to the GOST 859.
The copper nitrate solution with a mass concentration of 1 g/cm(g/DM):
1 g of copper metal is dissolved by heating in 15−20 cmof nitric acid (1:1).
The solution was cooled, transferred to a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.
Carbonyl iron brand PS according to GOST 13610.
Iron sulfate, a solution with a mass concentration of 1 g/cm(g/DM):
1 g of carbonyl iron is dissolved in 30 cmof sulphuric acid (1:4) when heated. Then poured carefully dropwise nitric acid until the termination of foaming solution. The solution was boiled, cooled, transferred to a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix.
1 cmof the solution contains 0.01 g of iron.
Arsenious anhydride mark «refined» according to GOST 1973.
Sodium mistakemistake ortho (NaAsO).
Standard solutions of arsenic.
Solution a: 0,132 g of arsenious anhydride is dissolved in 5 cmof sodium hydroxide solution with a mass concentration of 5 g/cm, (DM), dilute with water to 200 cm, and was added sulfuric acid (1:1) until neutral reaction on the universal indicator. The solution was transferred to 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. 0,256 g michalowskiego sodium ortho dissolved in 200 cmof water and then do as above in the preparation of a solution of arsenious anhydride.
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, is prepared immediately before use.
Solution: 10 cmstandard solution B is placed in a volumetric flask with a capacity of 100 cm, made up to the mark with water and mix is prepared immediately before use.
1 cmstandard solution contains 0,000001 g of arsenic.
(
Changed the wording, Rev. N 1, 2).
3.3. Analysis
3.3.1. Determination of arsenic after prior separation by Stripping in the form of arsenic trichloride
The weight of the alloy (tab.2) is placed in the beaker (or flask) with a capacity of 250−300 cm, 30 cm, pour themixture of hydrochloric and nitric acid, cover the beaker (or flask) watch glass and dissolve a portion of the alloys when heated. To the solution was added 15 cmof perchloric acid, evaporated the solution to start the selection, vapor perchloric acid and heated for 15−20 min for the oxidation of chromium (III) to chromium (VI).
Table 2*
___________________________
* Table.1. (Deleted, Rev. N 2).
| |
|
Mass fraction of arsenic, %
|
The mass of charge, g
|
From 0.0001 to 0.0005 to
|
1,0
|
SV. Of 0.0005 «to 0.001
|
0,5
|
«Of 0.001» to 0.002
|
0,25
|
«Of 0.002» to 0.005
|
0,1
|
Salt is dissolved in 100−120 cmwater when it is heated, pour 3 cmof a solution of iron sulfate and pre-separates the ammonia arsenic with the ferric hydroxide by adding ammonia solution prior to the precipitation of ferric hydroxide and excess of it 10−15 cm. The contents of the beaker (or flask) and heated for 5−10 min to coagulate the precipitate. The precipitate was filtered off on a medium density filter «white ribbon», washed 5−7 times with a hot solution of ammonia (1:500). The precipitate is dissolved on the filter in the 30−40 cmhot mixture of hydrochloric and nitric acids (1:1) in portions of 10 cm. Washed the filter with hot water 3−4 times, the filter is discarded.
To the filtrate is poured 10 cmof sulphuric acid, 10 cmof phosphoric acid (1:1) and evaporated to start the selection of sulfuric acid vapor. Wash the walls of the beaker (or flask) with water, and again evaporate the solution to start the selection of sulfuric acid vapor, is cooled. Carefully pour 5 cmof water, transfer the solution in the distillation flask, add 15 cmof hydrochloric acid, 0.5 g potassium bromide, 0.5 g of hydrazine sulphate and slowly heating the solution, distilled arsenic trichloride at a temperature not higher than 120 °C. the Distillate is collected in the beaker (or flask) capacity of 100 cm, which is pre-poured 10 cmof water. The Stripping is continued until until the receiver will not pass the initial volume of the solution.
To the distillate add 10 cmof nitric acid, evaporate the solution to wet salts; to the dry residue poured 5 cmof nitric acid and again evaporated to moist salts. The precipitate is dissolved in 5 cmof nitric acid (1:1) when heated, pour 5 cmof water, poured the solution into a volumetric flask with a capacity of 25 cm, top up to the mark with water and mix. Take a micropipette aliquot part of the resulting solution equal to 50 micysmf, enter it into a graphite cuvette and record the amount of radiation absorption by using a registered device. For measurements taken at least three alikvotnih parts of the solution.
Simultaneously with the execution of the determination carried out control experience in which pre-add 3 cmof a solution of sulphate of iron.
Mass of arsenic in test solution found by the calibration schedule subject to amendments the reference experiment.
(Modified, edited by
I, ISM. N 1).
3.3.2. Determination of arsenic after preliminary separation of thioacetamide as a sulfide
The weight of the alloy depending on the mass fraction of arsenic is determined by the table.2, is placed in the beaker (or flask) with a capacity of 250−300 cm, 30 cm, pour themixture of hydrochloric and nitric acids, cover beaker or flask with a watch glass and dissolve a portion of the alloy when heated. To the solution was added 15 cmof perchloric acid, the solution evaporated to release vapors of perchloric acid and heated for 15−20 min for the oxidation of chromium (III) to chromium (VI).
Salt is dissolved in 100−120 cmwater when it is heated, pour 3 cmof a solution of iron sulfate and pre-separates the ammonia arsenic with the ferric hydroxide by adding ammonia solution prior to the precipitation of ferric hydroxide and excess of it 10−15 cm. Solution and the precipitate was heated for 5−10 min to coagulate the precipitate. The precipitate was filtered off on a medium density filter «white ribbon», washed 5−7 times with a hot solution of ammonia (1:500) and dissolved on the filter with 50 cmof hot sulphuric acid (1:4) in portions of 10−15 cm. The filter was washed 5−6 times with hot water and discarded.
To the filtrate is poured 10 cmof tartaric acid solution, heat the solution for 10−15 min at 90 °C — 95 °C, cooled, poured ammonia solution to pH 8−9 by universal indicator solution and heated for 15−20 min at 90 °C — 95 °C until complete dissolution of the precipitate. The solution was poured sulfuric acid (1:1) to pH 2 by universal indicator and an excess of 10 cm, top up the solution with water to 180 cmand heated to boiling. Carefully add 1−2 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 spot plate, add another 10 cmof a solution of thioacetamide, then allowed to stand for 30−40 minutes at a temperature of 85 °C — 90 °C and cooled.
After 4 h, the precipitate filtered off sulphides in two medium density filter «white ribbon», washed 6−7 times with water, dissolve the sulphides in the 30−40 cmhot mixture of hydrochloric and nitric acids (1:1), in portions of 10 cm. The residue is washed on the filter with hot water 3−4 times, the filter is discarded. The solution was evaporated to wet salts; to the dry residue poured 5 cmof nitric acid and again evaporated to moist salts.
The precipitate is dissolved in 5 cmof nitric acid (1:1) when heated, pour 5 cmof water, poured the solution into a volumetric flask with a capacity of 25 cmof water, poured the solution into a volumetric flask with a capacity of 25 cm, top up to the mark with water and mix.* Take a micropipette aliquot part of the solution, equal to 50 micysmf, is introduced into a graphite cuvette and record the amount of radiation absorption by using a registered device. For measurements taken at least three alikvotnih parts of the solution.
_________________
* The text matches the original. — Note the manufacturer’s database.
Simultaneously with the execution of the determination carried out control experience in which pre-add 3 cmof a solution of sulphate of iron.
A lot of arsenic, as amended in the reference experiment find for the calibration schedule.
(Modified redakts
ia, Rev. N 1, 2).
3.3.3. Preparation of the device for measuring
Activation of the device, setting the spectrophotometer at a resonance radiation of 193.7 nm, the adjustment of the control unit block the atomization is carried out according to the instructions supplied with the device.
The conditions of determination of arsenic:
The analytical line of 193.7 nm.
The spectral slit width of 0.7 nm.
Time of drying at 145 °C — 15 s
The decomposition at 900 °C — 12 s
Time atomization at 2250 °C — 5 s.
The determination is carried out in a minimal flow of gas at the atomization stage.
3.3.4. Construction of calibration curve
Six glasses or flasks with a capacity of 250−300 cmis placed 0.5 grams of Nickel powder. Five cups (or flasks) poured consistently 1,0; 2,0; 3,0; 4,0; 5,0 cmstandard solution of arsenic. The sixth beaker (or flask) used for carrying out control of the experience. In all the cups (or flasks) and add 3 cmof a solution of sulphate of iron and 30 cmof a mixture of hydrochloric and nitric acids and 15 cmof perchloric acid. The solutions were evaporated until the appearance of fumes of perchloric acid and then act as described in the claims.3.3.1 and 3.3.2. From the values of absorbance of analyzed solutions is subtracted the value of optical density in the reference experiment.
On the found values of optical density of the solutions and their corresponding values of the concentrations of arsenic to build the calibration graph.
3.3.3, 3.3.4. (Changed edition, Rev. N 2).
3.4. Processing of the results
3.4.1. Mass fraction of arsenic () in percent is calculated by the formula
,
where is the mass of arsenic, was found in the calibration schedule g;
— the weight of the portion of alloy,
3.4.2. The absolute differences of the results of the parallel definitions should not exceed (at p = 0.95) of permissible values, specified in table.3.
Table 3
| |
|
Mass fraction of arsenic, %
|
The absolute allowable difference, %
|
0.0001 0.0002 incl.
|
0,0001
|
SV. Of 0.0002 «to 0.0005 «
|
0,0002
|
«Of 0.0005» to 0.001 «
|
0,0005
|
«Of 0.001» to 0.002 «
|
0,001
|
«Of 0.002» to 0.005 «
|
0,0015
|
(Changed edition, Rev. N 2).
