GOST 12072.2-79
INTERSTATE STANDARD
CADMIUMMethods of iron determinationCadmium. |
GOST |
Date of introduction 01.12.80
This standard sets the photometric and atomic absorption methods for the determination of iron (at mass fraction of iron from from 0.0002% to 0.1%). The standard fully complies ST SEV 917−78.
(Changed edition, Rev. No. 1).
1. GENERAL REQUIREMENTS
1.1. General requirements for method of analysis and safety requirements according to GOST 12072.0.
(Changed edition, Rev. No. 2).
2. PHOTOMETRIC METHOD
2.1. The essence of the method
The method is based on formation of yellow sulfosalicylic iron complex in ammonium environment and fotomaterialy it in the region of wavelengths 413−420 nm.
2.2. Apparatus, materials and reagents
Spectrophotometer or photoelectrocolorimeter of any kind for measurements in the visible region of the spectrum.
Hydrochloric acid according to GOST 3118, further purified by distillation in quartz apparatus or method of saturation with deionized water. From purified acid to prepare solutions of hydrochloric acid 6 and 2 mol/DM3.
All hydrochloric acid solutions stored in polyethylene or quartz container.
Hydrochloric acid according to GOST 14261.
Nitric acid according to GOST 4461.
Sulfosalicylic acid according to GOST 4478, a solution of 200 g/DM3.
Ammonia water according to GOST 3760.
Hydrogen peroxide (peroxide) according to GOST 10929.
Iron powder restored brand MLB-1 according to GOST 9849 or iron (III) oxide on the other 6−09−5346.
Standard solutions of iron.
Solution a: a sample weighing 0,500 g of iron powder or 0,7149 g of iron (III) oxide are dissolved in 20 cm3 of hydrochloric acid with the addition of 7−8 drops of hydrogen peroxide solution in a conical flask with a capacity of 250 cm3. The excess of hydrogen peroxide destroy the careful boiling, the solution was cooled and quantitatively transferred to a volumetric flask with a capacity of 500 cm3, made up to the mark with water and mix.
1 cm3 of solution contains 1 mg of iron.
Solution B: in a volumetric flask with a capacity of 100 cm3 measure with a pipette 10 cm3 of solution A, pour 10 cm3 of hydrochloric acid 2 mol/DM3, made up to the mark with water and mix.
1 cm3 of a solution contains 0.1 mg of iron.
Solution: in a volumetric flask with a capacity of 100 cm3 measure 10 cm3 of a solution, pour 10 cm3 of hydrochloric acid 2 mol/DM3, made up to the mark with water and mix.
1 cm3 of solution contains 0.01 mg of iron.
(Changed edition, Rev. No. 3).
2.3. Analysis
2.3.1. The weight of cadmium weight of 2,500 grams (mass fraction of iron from from 0.0002% to 0.01%) or 1,000 g (mass fraction of iron St of 0.01%) was placed in a conical flask with a capacity of 250 cm3, poured 20 cm3 of the hydrochloric acid solution 6 mol/dm3, 1 cm3 of nitric acid and heated until complete dissolution of the sample and removal of nitrogen oxides.
When the mass fraction of iron St. 0,003% solution of the sample was cooled, transferred to a volumetric flask with a capacity of 100 cm3, made up to the mark with water and mix in accordance with table. 1 select aliquot part of the solution was placed in a volumetric flask with a capacity of 50 cm3. When the mass fraction of iron from from 0.0002% to 0.003% solution of the sample is cooled, transfer it into a volumetric flask with a capacity of 50 cm3 small amount of water.
Table 1
| Mass fraction of iron, % | The weight of cadmium, g | The volume of the volumetric flask for dilution of the solution sample cm3 |
Aliquota part of the solution for determination of iron, see3 |
| From of 0.0002 to 0.003 | 2,500 | - | The entire solution |
| SV. Of 0.003 «to 0.01 | 2,500 | 100 | 20 |
| «To 0.01» to 0.05 | 1,000 | 100 | 10 |
| «0,05» 0,1 | 1,000 | 100 | 5 |
In volumetric flasks taken aliquote part or the entire solution of the sample flow 10 cm3 of a solution of sulfosalicylic acid, ammonia to the yellow color of the solution, give the excess of the last 5 cm3, made up to the mark with water and mix.
Optical density of the solution measured in a cuvette with a thickness of the light absorbing layer 50 mm in the region of wavelengths 413−420 nm. Solution comparison is the solution of the reference experiment.
The iron content is set according to the calibration schedule.
(Changed edition, Rev. No. 3).
2.3.2. To build a calibration curve in nine out of ten volumetric flasks with a capacity of 50 cm3 metered 0,5; 1,0; 2,0; 3,0; 4,0; 5,0; 6,0; 7,0 and 8.0 cm3 solution (corresponding to 5; 10; 20; 30; 40; 50; 60; 70 and 80 mcg of iron). Poured into each flask, 10 cm3 of a solution of sulfosalicylic acid and then act as described in section
According to the obtained values of optical density of solutions and their corresponding grades of iron to build the calibration graph.
3. ATOMIC ABSORPTION METHOD
3.1. The essence of the method
The method is based on measurement of the absorption of the analytical line of iron at a wavelength of 248.3 nm with the introduction of solutions of the analyzed sample and calibration solutions in the air-acetylene flame. A portion of the cadmium pre-transferred into solution by acid decomposition.
3.2. Apparatus, materials and reagents
Atomic absorption spectrophotometer any brand with a radiation source for iron. Air, compressed under a pressure of 2105 — 6105 PA (2−6 ATM). Acetylene in the cylinder.
Nitric acid according to GOST 11125, diluted 1:1, and a solution of 2 mol/DM3. Iron powder restored brand MLB-1 according to GOST 9849 or iron (III) oxide on the other 6−09−5346.
Standard solutions of iron.
Solution a: the sample weight 0,100 g of iron powder or 0,143 g of iron (III) oxide was placed in a beaker with a capacity of 250 cm3, pour 20 cm3 of nitric acid, diluted 1:1, heated to complete dissolution, cooled and quantitatively transferred to a volumetric flask with a capacity of 1 DM3, made up to the mark with water and mix.
1 cm3 of solution A contains 0.1 mg of iron.
Solution B: 25 cm3 of solution A is placed in a volumetric flask with a capacity of 250 cm3, made up to the mark with water and mix.
1 cm3 of a solution contains 0.01 mg of iron.
Cadmium GOST 1467 or GOST 22860, iron containing not more than 410-4 %, a solution of 100 g/DM3; 100 g of cadmium in the form of pieces or shavings dissolved in 200−250 cm3 of nitric acid. Pour the acid slowly, in small portions (about 10 cm3). If you add another portion of acid, the reaction goes slowly, poured the resulting solution of cadmium nitrate to another flask and continue the decomposition. Then combine all the solution, boil to remove oxides of nitrogen, diluted with water, transferred into a measuring flask with volume capacity of 1000 cm3 and mixed.
(Changed edition, Rev. No. 1, 3).
3.3. Analysis
3.3.1. The weight of cadmium weight of 1,000−5,000 grams is placed in a conical flask with a capacity of 250 cm3, poured 15−25 cm3 of nitric acid, diluted 1:1, heated until complete dissolution of the metal and remove oxides of nitrogen. Pour 20−25 cm3 of water, stirred, cooled, quantitatively transferred to a volumetric flask with a capacity of 100 cm3, made up to the mark with water and mix. The sample solution and the calibration solutions is injected into air-acetylene flame and measuring the absorption of the analytical line of 248.3 nm for iron GOST 12072.0.
If necessary, in solution of the sample can be determined also the content of thallium, lead, zinc, copper and Nickel.
3.3.2. To construct the calibration graphs prepared two series of calibration solutions.
I series: in nine out of ten volumetric flasks with a capacity of 100 cm3 metered 1,0; 2,0; 5,0 and 10,0 cm3 standard solution and 2,0; 4,0; 6,0; 8,0 and 10,0 cm3 of a standard solution A (which corresponds to 0,1; 0,2; 0,5; 1,0; 2,0; 4,0; 6,0; 8,0 and 10.0 mg/DM3 iron) into each flask pour 10 cm3 of a solution of nitric acid 2 mol/DM3, topped up to the mark with water and mix. The basis of these calibration solutions is water.
II series: in four of the five volumetric flasks with a capacity of 100 cm3 metered 1,0; 2,0; 5,0 and 10,0 cm3 of a standard solution B (which corresponds to 0,1; 0,2; 0,5 and 1,0 mg/DM3 iron) into each flask pour 10 cm3 of a solution of nitric acid 2 mol/DM3, 50 cm3 of a solution of cadmium 100 g/DM3, made up to the mark with water and mix. The basis of these calibration solutions is the solution of cadmium. For the calibration solutions I series measure solutions of unknown samples from a sample with a mass of 1,0−2,5; II a series of calibration solutions is used to analyze the solutions of analyzed samples from a sample weighing 5 g.
In the determination of one solution of thallium, lead, zinc, copper and Nickel in each of the above flasks one of a series of calibration solutions add such amounts of standard solutions of the elements that would correspond to their concentrations in the calibration solutions.
3.3.1,
3A. ATOMIC ABSORPTION METHOD
(when the mass fraction of iron from from 0.0002% to 0,006%)
3A.1. The essence of the method
The method is based on coprecipitation of iron hydroxide with a hydroxide of lanthanum, the dissolution of hydroxides with hydrochloric acid and measuring the absorption of the analytical line of 248.3 nm iron with the introduction of the solutions into an air-acetylene flame.
(Added, Rev. No. 1).
3A.2. Apparatus, reagents and materials
Atomic absorption spectrophotometer of any brand.
The air compressed under pressure (5−6 ATM) 2105 — 6105 PA (2−6 ATM).
Acetylene in cylinders.
Hydrochloric acid according to GOST 14261 and a solution of 1:1.
Iron powder restored brand MLB-1 according to GOST 9849 or iron (III) oxide on the other 6−09−5346.
Ammonia water according to GOST 3760 and a solution of 1:19.
Peroxide (peroxide) of hydrogen according to GOST 10929.
Nitric acid according to GOST 11125 and a solution of 1:20.
Lanthanum nitrate La (NO3)36H2 O, on the other 6−09−4676, a solution of 1 g/DM3 Lantana: 0,3115 g of salt are dissolved in 20 cm3 of water with a few drops of nitric acid.
The solution is poured into a measuring flask with a capacity of 100 cm3, made up to the mark with water and mix.
Standard iron solution prepared according to claim
3A.3. Analysis
The hitch weight of 5,000 g was placed in a heat-resistant glass with a capacity of 250−300 cm3, flow of 15 cm3 of nitric acid and decomposed under the watch glass when heated. The resulting solution is evaporated to a syrupy condition (on the surface of bubbles appear), remove from heat, add 70 cm3 of water and 5 cm3 of a solution of lanthanum was mixed by rotating the glass. It is then heated to a temperature of 70 °C and poured gradually to 20−25 cm3 of ammonia until the complete disappearance of abundant flocculent precipitate of cadmium hydroxide.
The solution is allowed to stand for 30 min at the edge of the plate. During this time, the bottom of the glass will appear white, but with sufficient content of iron of a reddish precipitate. The precipitate was filtered off, washed 2−3 times with hot solution of ammonia (1:19) and wash with filter water into a glass, which was carried out the deposition. The filter is washed with 25−30 cm3 of hot hydrochloric acid (1:1) with the addition of 3−5 drops of hydrogen peroxide and then with hot water. Boil the resulting solution to remove excess hydrogen peroxide and obtain a volume of approximately 1 cm3. Poured 1.5 cm3 of hydrochloric acid and transferred to a volume of 20 cm3 using a measuring cylinder.
Measure the magnitude of the absorption of the iron line of 248.3 nm according to GOST 12072.0.
If the sensitivity of the device is not able to measure iron in the translation of hitch weight 5,000 g in a volume of 20 cm3, it is possible to use a weighed mass of 10.00 g when translated into the volume of 10 cm3. The number of nitric acid for the decomposition of samples and the amount of ammonia is doubled, and the amount of hydrochloric acid consumed in the translation of the volume is halved or replaced by the same quantity of hydrochloric acid solution (1:1).
To build a calibration curve in eight of the nine volumetric flasks with a capacity of 100 cm3 measured 5.0 and 10.0 cm3 of a standard solution and 2,0; 4,0; 6,0; 8,0; 10,0 and 12,0 cm3 of a standard solution And in each flask add 15 cm3 of hydrochloric acid solution (1:1), made up to the mark with distilled water and mix. The obtained iron concentration in the calibration samples correspond to: 0,5; 1,0; 2,0; 4,0; 6,0; 8,0; 10,0 and 12.0 mg/DM3.
3A.2, 3A.3. (Changed edition, Rev. No. 1, 3).
4. PROCESSING OF THE RESULTS
4.1. Mass fraction of iron (X), % if the photometric determination is calculated by the formula
where t — the weight of the portion corresponding to the selected aliquote part of the solution, g;
m1 — quantity of iron found in the solution of the analyzed sample according to the calibration schedule, mcg.
4.2. Mass fraction of iron (X), %, in atomic absorption the determination is calculated by the formula
where With1 — mass concentration of iron in the sample solution, mg/DM3;
With2 — mass concentration of iron in solution in the reference experiment, mg/DM3;
V — volume of the volumetric flask, cm3;
t — the weight of the portion,
(Changed edition, Rev. No. 1, 3).
4.3. Allowable absolute discrepancies in the results of parallel measurements and the results of the analysis shall not exceed the values given in table. 2.
Table 2
| Mass fraction of iron, % | The permissible difference for parallel definitions % | The permissible discrepancy between the results of the analysis % |
| From 0,0002 to 0,0003 incl. | 0,0001 | 0,0001 |
| SV. 0,0003 «0,0010 « | 0,0002 | 0,0003 |
| «0,0010» 0,0030 « | 0,0003 | 0,0004 |
| «0,0030» 0,0100 « | 0,0010 | 0,0013 |
| «0,010» 0,040 « | 0,002 | 0,003 |
| «0,040» 0,100 « | 0,005 | 0,006 |
(Changed edition, Rev. No. 3).
INFORMATION DATA
1. DEVELOPED AND INTRODUCED by the Ministry of nonferrous metallurgy of the USSR
2. APPROVED AND put INTO EFFECT by Decision of the USSR State Committee for standards from
3. The standard fully complies ST SEV 917−78
4. REPLACE GOST 12072.2−71
5. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS
| The designation of the reference document referenced | The number of the paragraph, subparagraph | The designation of the reference document referenced | The number of the paragraph, subparagraph |
| GOST 1467−93 | 3.2 | GOST 11125−84 | 3.2, 3A.2 |
| GOST 3118−77 | 2.2 | GOST 12072.0−79 | 1.1, 3.3.1, 3A.3 |
| GOST 3760−79 | 2.2, 3A.2 | GOST 14261−77 | 2.2, 3A.2 |
| GOST 4461−77 | 2.2 | GOST 22860−93 | 3.2 |
| GOST 4478−78 | 2.2 | THAT 6−09−4676−78 | 3A.2 |
| GOST 9849−86 | 2.2, 3.2, 3A.2 | THAT 6−09−5346−87 | 2.2, 3.2, 3A.2 |
| GOST 10929−76 | 2.2, 3A.2 |
