GOST 15027.18-86
GOST 15027.18−86 Bronze without tin. Methods for determination of chromium (Change No. 1)
GOST 15027.18−86
Group B59
INTERSTATE STANDARD
BRONZE WITHOUT TIN
Methods for determination of chromium
Tinless bronze.
Methods for determination of chromium
AXTU 1709
Date of introduction 1987−01−01
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. INTRODUCED FOR THE FIRST TIME
4. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS
| The designation of the reference document referenced | Section number, paragraph, sub-paragraph |
| GOST 859−2001 |
2.2 |
| GOST 1277−75 |
3.2 |
| GOST 2567−89 |
2.2; 3.2 |
| GOST 3118−77 |
2.2; 3.2 |
| GOST 4204−77 |
3.2 |
| GOST 4208−72 |
3.2 |
| GOST 4220−75 |
2.2; 3.2 |
| GOST 4461−77 |
2.2; 3.2 |
| GOST 5457−75 |
2.2 |
| GOST 5905−79 |
2.2 |
| GOST 9293−74 |
2.2 |
| GOST 18175−78 |
Chapeau |
| GOST 20478−75 |
3.2 |
| GOST 25086−87 |
1.1; 2.4.2 b; 3.4.4 |
5. The expiration time limit is removed by the Resolution of Gosstandart of the USSR from
6. EDITION with Change No. 1, approved in October 1991 (IUS 1−92)
This standard establishes the atomic absorption and potentiometric methods for the determination of chromium (in mass fraction of chromium of from 0.2% to 1.5%) in tin bronze according to GOST 18175.
The standard fully complies ST SEV 5007−85.
1. GENERAL REQUIREMENTS
1.1. General requirements for methods of analysis GOST 25086 when two parallel definitions.
2. ATOMIC ABSORPTION METHOD
2.1. The essence of the method
The method is based on dissolving the samples in nitric, hydrofluoric and perchloric acids and the measurement of atomic absorption of chromium in the flame acetylene-air or acetylene-nitrous oxide at a wavelength 357,9 nm.
2.2. Apparatus, reagents and solutions
Atomic absorption spectrometer with all accessories.
Nitrous oxide according to GOST 9293.
A radiation source for chromium.
Acetylene according to GOST 5457.
Nitric acid according to GOST 4461, diluted 1:1.
Hydrochloric acid according to GOST 3118, diluted 1:1.
Hydrofluoric acid according to GOST 2567.
Chloric acid, diluted 1:1.
Copper of mark M0 GOST 859.
Standard copper solution: 5 g of copper is dissolved in 50 cmof a solution of nitric acid, the solution was boiled to remove oxides of nitrogen. The solution was then cooled, placed in a volumetric flask with a capacity of 100 cm
, made up to the mark with water and mix.
1 cmof the solution contains 0.05 g of copper.
Chrome brand Х99Б according to GOST 5905.
Potassium dichromate according to GOST 4220.
Standard solutions of chromium.
Solution a: 0.5 g chromium dissolved in 25 cmof a solution of hydrochloric acid or 1,4145 g of potassium dichromate, previously dried at 150 °C to constant weight and dissolve in water. The solutions were transferred to volumetric flasks with a capacity of 500 cm
, made up to the mark with water and mix.
1 cmof the solution contains 0.001 g of chromium.
Solution B: 10 cmsolution And placed in a volumetric flask with a capacity of 100 cm
, made up to the mark with water and mix.
1 cmof a solution contains 0.0001 g khro
mA.
2.3. Analysis
2.3.1. A portion of sample weighing 0.5 g was placed in a platinum Cup, add 10 cmof nitric acid solution, 5 cm
hydrofluoric acid and dissolved first in cold and then when heated. After dissolution, add 10 cm
of hydrochloric acid and evaporated to the beginning of the smoke of perchloric acid. After cooling, add 50 cm
of water and heated to dissolve the salts. The solution was cooled, transferred to a volumetric flask with a capacity of 250 cm
, made up to the mark with water and mix. Aliquot part of 25 cm
is placed in a volumetric flask with a capacity of 100 cm
, made up to the mark with water and mix.
Measure the atomic absorption of chromium in the flame acetylene-air or acetylene-nitrous oxide at a wavelength 357,9 nm parallel to the sample solution, the solution control experience and solutions to build the calibration curve. The concentration of chromium found at the calibration schedule
.
2.3.2. Construction of calibration curve
Nine volumetric flasks with a capacity of 100 cmplaced at 1 cm
of a solution of copper; eight of them add 1,0; 2,0; 3,0; 4,0; 5,0; 6,0; 7,0 and 8.0 cm
of a solution of chromium, which corresponds to 0,1; 0,2; 0,3; 0,4; 0,5; 0,6; 0,7 and 0.8 mg of chromium. To all flasks add 1 cm
of a solution of perchloric acid, made up to the mark with water and mix. Measure the atomic absorption of chromium immediately before and after measuring the sample solution. According to the obtained values build the calibration graph.
2.4. Processing of the results
2.4.1. Mass fraction of chromium () in percent is calculated by the formula
where is the concentration of chromium in the sample solution found by the calibration schedule, g/cm
;
the concentration of chromium in solution in the reference experiment, was found in the calibration schedule, g/cm
;
— the volume of the final sample solution, cm
;
— the weight of the portion corresponding to aliquote part of the solution, g
.
2.4.2. Discrepancies in the results of parallel definitions should not exceed the values permitted by the divergence (
the rate of convergence) specified in the table.
(Changed edition, Rev. N 1).
2.4.2. Discrepancies in the results analysis, obtained in two different laboratories or two of the results of analysis obtained in the same laboratory but under different conditions (a measure of reproducibility) shall not exceed the values given in the table.
| Mass fraction of chromium, % |
|
|
| From 0.2 to 0.5 incl. |
0,03 | 0,04 |
| SV. 0,5 «1,0 « |
0,05 | 0,07 |
| «1,0» 1,5 « |
0,08 | 0,11 |
2.4.2 b. Control of accuracy of analysis results is carried out by additives or by comparison of the results obtained by the potentiometric method, in accordance with GOST 25086.
2.4.2 a, 2.4.2 b. (Added, Rev. N 1).
2.4.3. The differences in the assessment of the quality bronzes determination of chromium performed by atomic absorption method.
3. POTENTIOMETRIC METHOD
3.1. The essence of the method
The method is based on dissolving the sample in nitric and sulphuric acids with the addition of hydrofluoric acid, the oxidation of chromium (III) neccersarily ammonium in the presence of silver nitrate to chromium (VI) and potentiometric titration of chromium salt solution Mora.
3.2. Apparatus, reagents and solutions
The setup for potentiometric titration with a saturated calomel electrode and a platinum indicator electrode.
Nitric acid according to GOST 4461, diluted 1:1.
Sulfuric acid according to GOST 4204, diluted 1:1.
Hydrofluoric acid according to GOST 2567.
Hydrochloric acid according to GOST 3118, diluted 1:3.
Silver nitrate according to GOST 1277, a solution of 2.5 g/DM.
Ammonium neccersarily according to GOST 20478, solution 100 g/l, freshly prepared.
Potassium dichromate according to GOST 4220, is 0.017 M solution: 2,4517 g of potassium dichromate, previously dried at 150 °C to constant weight, dissolved in water, transferred to a measuring flask with volume capacity of 1000 cm, made up to the mark with water and mix.
Allowed preparation of the solution of fiksanala.
1 cmof the solution contains 0,0008667 g of chromium.
Salt of protoxide of iron and ammonium double sulfate (salt Mora) according to GOST 4208, 0.05 mol/DMsolution: 19,6 g of Mohr salt dissolved in 800 cm
of water containing 60 cm
of sulfuric acid solution, cooled, transferred into a measuring flask with volume capacity of 1000 cm
, made up to the mark with water and mix.
The installation of the mass concentration of salt solution Mora: 20 cmsolution of potassium dichromate is placed in a beaker with a capacity of 600 cm
add 6 cm
of sulfuric acid solution, diluted with water to a volume of 300 cm
and potentiometric titrated with a solution of salt Mora.
Mass concentration of solution (), expressed in grams of chromium per 1 cm
of a solution, calculated by the formula
where is the volume of solution of potassium dichromate, taken for titration, cm
;
— the volume of salt solution Mora, used for titration, cm
;
0,0008667 — weight chromium, corresponding to 1 cmof a solution of potassium dichromate,
(Changed edition, Rev. N 1).
3.3. Analysis
A portion of the sample weighing 2 g were placed in a glass with a capacity of 600 cm, adding 25 cm
of a solution of nitric acid with the addition of 5 drops of hydrofluoric acid and dissolved first in cold and then when heated. After dissolution, add 30 cm
of sulfuric acid solution and the solution is evaporated until the beginning of the smoke of sulfuric acid, cooled, rinse walls of beaker with water and carefully add 300 cm
water and 15 cm
of a solution of silver nitrate, 40 cm
of a solution of ammonium naternicola and contribute to the solution of a few glass beads. The glass is covered with glass and boil for 15 minutes Add 5 cm
of hydrochloric acid, boil for 10 minutes, cooled to room temperature and titrate chromium (VI) potentiometric salt solution Mora to the jump potential
.
3.4. Processing of the results
3.4.1. Mass fraction of chromium () in percent is calculated by the formula
where — the volume of salt solution Mora, used for titration, cm
;
mass concentration of salt solution Mora, g/cm
;
— the weight of the portion of the sample,
3.4.2. Discrepancies in the results of parallel definitions should not exceed the values permitted by the divergence (
the rate of convergence) specified in the table.
3.4.1,
3.4.3. Discrepancies in the results analysis, obtained in two different laboratories or two of the results of analysis obtained in the same laboratory but under different conditions (a measure of reproducibility) shall not exceed the values given in the table.
3.4.4. Control of accuracy of analysis results is carried out by additives or by comparison of the results obtained by atomic absorption method, in accordance with GOST 25086.
3.4.3,
