GOST 23859.3-79
GOST 23859.3−79 heat-resistant Bronze. Methods for determination of chromium (with Amendments No. 1, 2)
GOST 23859.3−79
Group B59
INTERSTATE STANDARD
BRONZE HIGH-TEMPERATURE
Methods for determination of chromium
Bronze fire-resistance. Methods for the determination of chromium
AXTU 1709
Date of introduction 1981−01−01
Resolution of the USSR State Committee for standards, dated 16 October 1979, N 3937 time of the introduction set with 01.01.81
Limitation of actions taken by Protocol No. 5−94 of the Interstate Council for standardization, Metrology and certification (ICS 11−12−94)
EDITION with Amendments No. 1, 2 approved in June 1985, March 1990 (IUS 9−85, 7−90).
This standard establishes titrimetric and photometric methods for the determination of chromium (in mass fraction it from 0.15 to 1.3%) in high-temperature copper alloys.
(Changed edition, Rev. N 2).
1. GENERAL REQUIREMENTS
1.1. General requirements for method of analysis according to GOST 25086−87 with the addition of a GOST 23859.1−79, sec. 1.
(Changed edition, Rev. N 2).
Titrimetric method for the determination of chromium
The method is based on the oxidation of chromium (III) to chromium (IV) neccersarily ammonium in sulfate medium in the presence of silver nitrate as a catalyst, the recovery of chromium (VI) excessive amount of salt Mora and the determination of the excess iron (II) potentiometric titration solution of potassium dichromate or potassium permanganate solution with the visual setting of the end of the titration.
2. APPARATUS, REAGENTS AND SOLUTIONS
Potentiometer LPM-60 M or other equivalent device.
The platinum electrode ETPL-01M.
The reference electrode ratnaswamy, silver chloride, saturated calomel, or tungsten.
Nitric acid GOST 4461−77 diluted 1:1.
Hydrofluoric acid according to GOST 10484−78.
Sulfuric acid GOST 4204−77, diluted 1:1 and 1:9 and 1 M solution.
Silver nitrate according to GOST 1277−75, a solution of 0.6 g/DM.
Sodium oxalate according to GOST 5839−77.
Ammonium neccersarily according to GOST 20478−75, a solution of 250 g/DM.
Salt of protoxide of iron and ammonium double sulfate (salt Mora) according to GOST 4208−72, 0.05 M and 0.01 M solutions are prepared as follows: or 19,6 39,2 g of salt Mora dissolved in a small volume of sulfuric acid, diluted 1:9, and transferred to volumetric flask with a capacity of 1 DMfor receiving, respectively, 0.05 M and 0.01 M solution and topped up to the mark with the same acid.
Potassium dichromate according to GOST 4220−75, 0,017 and 0,034 M solutions; prepare fiksanala or by: 2,4518 g or 4,9037 g of potassium dichromate dissolved in water, the solution was transferred to volumetric flask with a capacity of 1 DMand topped to the mark with water, 1 cm
0,034 M solution corresponds to 0,001734 g of chromium, and 1 cm
is 0.017 M solution corresponds to 0,000867 g of chromium.
Potassium permanganate according to GOST 20478−75, 0.01 M and 0.02 M solutions are prepared of fiksanala or as follows: 1.6 or 3.2 g of potassium permanganate dissolved in a beaker with a capacity of 500 cm250 cm
boiled and cooled water, allowed to settle and decanted by decantation in the flask with a capacity of 1 DM
. In the glass, again pour the 250 cm
of water, mixed well, settled, and again deytroyt solution in the same flask. The solution in the flask was diluted to the mark with water, mixed, poured into a bottle made of dark glass and leave to stand for 7−10 days. in a dark place.
The installation of the mass concentration of the solution of potassium permanganate. 0.2 g of sodium oxalate, dried at 100−105 °C, placed in a conical flask with a capacity of 250 cm, add 100 cm
of hot (80−90 °C) of water, add 10 cm
to 1 M sulfuric acid solution and titrated solution of potassium permanganate with constant stirring, until the advent laboratornogo staining. The first titration is carried out slowly, without adding further drops until until the previous is completely discolored.
The correction factor () potassium permanganate solution is calculated by the formula
where is the volume of potassium permanganate solution consumed for titration, cm
;
— weight of sodium oxalate, g;
0,0067002 — weight of sodium oxalate, corresponding to 1 cmprecisely 0,02 M solution potassium permanganate,
Mass concentration () potassium permanganate solution is calculated by the formula
where — correction factor;
0,001734 mass concentration is exactly 0.02 M solution of potassium permanganate for the chrome.
Sec. 2. (Changed edition, Rev. N 1, 2).
3. ANALYSIS
3.1. When the mass fraction of chromium from 0.15 to 1.3%.
Sample of bronze weighing 2 g was placed in a platinum Cup, add 2−3 cmhydrofluoric acid, 20 cm
of nitric acid and dissolved by heating. After dissolution of the wall of the rinse water, add 30 cm
of sulphuric acid diluted 1:1, and evaporated until a white smoke of acid. The residue is cooled, add 30−50 cm
of water and dissolved by heating. The solution is placed in a beaker with a capacity of 300 cm
, dilute with water to 150 cm
and produce copper by electrolysis when a current of 1.5−2 And the bleaching solution. The electrolyte transferred to a conical flask with a capacity of 500 cm
, rinse the glass with water, the solution diluted with water to 300 cm
and washed with 10 cm
of ammonium nitrate solution. The mixture is boiled until the complete destruction of excess ammonium naternicola that is determined by the termination of allocation of bubbles of oxygen. The solution was cooled, added from a burette 0.05 M solution of salt Mora for the mass concentration of chromium up to 0.5% or 0.1 M for the mass concentration of chromium in excess of 0.5% to transition yellow to green and 10 cm
in excess. The excess of salt Mora titrated 0.1 or 0.02 M potassium permanganate solution until the appearance of pale purple staining.
In potentiometric titrations the oxidation of chromium and all further operations are carried out in the glass. The excess of salt Mora titrated potentiometric or 0,017 0,034 M solution of potassium dichromate.
In both variants of the display to the titrated solution add the volume of salt solution Mora, equal to the amount added during the titration of the sample, and re-titrated by solution of potassium permanganate or bichromate of potassium, as specified in
up.
3.2. When the mass fraction of chromium from 0.4 to 1.3%.
The weight of bronze weighing 2 g was placed in a platinum Cup, add 2−3 cmhydrofluoric acid, 20 cm
of nitric acid and dissolved by heating.
After dissolving the walls of the Cup then rinsed with water, and add 30 cmof sulphuric acid diluted 1:1, and is evaporated until a white smoke of sulfuric acid. The solution was cooled, rinse the walls of the Cup with 3−5 cm
of water and again repeat the evaporation until a white smoke of sulfuric acid.
The residue is cooled, add 30−50 cmof water and dissolved by heating.
The solution was transferred to a conical flask with a capacity of 500 cm, rinse the Cup with water, the solution diluted with water to 300 cm
, flow 10 cm
of a solution of silver nitrate and 10 cm
solution naternicola ammonium. The mixture is boiled until the complete destruction of excess ammonium naternicola that is determined by the termination of allocation of bubbles of oxygen. The solution was cooled, added from a burette 0.1 M solution of salt Mora before moving greenish-yellow color in light blue and 10 cm
in excess.
The excess of salt Mora titrated with 0.02 M potassium permanganate solution until the appearance of purple staining.
In potentiometric titrations the oxidation of chromium and all further operations are carried out in the glass. The excess of salt Mora titrated potentiometric 0,034 M solution of potassium dichromate.
In both variants of induction to the titrated solution add the volume of salt solution Mora, equal to the amount added during the titration of the sample, and re-titrated by solution of potassium permanganate or potassium bichromate as above.
Sec. 3. (Changed edition, Rev. N 1).
4. PROCESSING OF THE RESULTS
4.1. Mass fraction of chromium () in percent is calculated by the formula
where is the volume of a solution of dichromate or potassium permanganate spent for titration of 10 cm
salt Mora, cm
;
— the volume of a solution of dichromate or potassium permanganate consumed in the titration of excess of salt Mora, cm
;
— mass concentration of a solution of dichromate or potassium permanganate for the chrome, g;
— the weight of the portion,
(Changed edition, Rev. N 1, 2)
.
4.2. Discrepancies in the results of three parallel definitions should not exceed the values permitted by the divergence (
the rate of convergence), calculated according to the formula
where — mass fraction of chromium, %.
(Changed edition, Rev. N 2).
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 calculated according to the formula
where — mass fraction of chromium, %.
4.4. Control of accuracy of analysis results is carried out according to State standard samples of high-temperature (chromium) bronze or comparison of the results obtained by atomic absorption method, in accordance with GOST 25086−87.
4.5. Method is used when the differences in quality assessment of high-temperature bronzes.
4.3−4.5. (Added, Rev. N 2).
The photometric method for the determination of chromium
The method is based on the formation of chromium (VI) with diphenylcarbazide painted in purple color complex and the measurement of the optical density of the resulting solution.
5. APPARATUS, REAGENTS AND SOLUTIONS
Photoelectrocolorimeter or spectrophotometer.
Nitric acid GOST 4461−77 diluted 1:1.
Sulfuric acid GOST 4204−77, diluted 1:1 and 1:4.
Hydrofluoric acid according to GOST 10484−78.
Orthophosphoric acid according to GOST 1497−84.
A mixture of acids: to 50 cmof water was added 40 cm
of sulfuric acid and 40 cm
of phosphoric acid.
Silver nitrate according to GOST 1277−75, a solution of 4 g/DM.
Ammonium neccersarily according to GOST 20478−75, a solution of 80 g/DM.
Potassium dichromate according to GOST 4220−75.
Rectified ethyl alcohol GOST 18300−87.
Diphenylcarbazide, a solution of 1.5 g/DM: 0.15 g of the reagent was placed in a volumetric flask with a capacity of 100 cm
, add 15 cm
of ethyl alcohol, leave for 5−10 min, heated to dissolve, made up to the mark with water and mix.
Standard solutions of chromium
Solution a: 0,283 g of potassium dichromate, previously dried at 140−150 °C, dissolved in water, the solution transferred to a volumetric flask with a capacity of 500 cm, top up to the mark with water and mix.
1 cmof the solution contains 0.0002 g of chromium.
Solution B: 10 cmof solution A was placed in a volumetric flask with a capacity of 100 cm
, made up to the mark with water and mix.
1 cmof solution B contains 0,00002 g of chromium.
Sec. 5. (Changed edition, Rev. N 2).
6. ANALYSIS
6.1. The sample of bronze with a mass of 0.25 g is placed in a platinum Cup, add 10 cmof nitric acid, 1−2 cm
hydrofluoric acid and dissolved by heating. After dissolution, the solution was cooled, add 5 cm
of sulphuric acid (1:1) and removed prior to the allocation of white smoke of sulfuric acid. A Cup of cool, dissolve salt in 30−40 cm
of hot water when heated. The solution was transferred to a beaker with a capacity of 250−300 cm
, add 10 cm
boiled nitric acid (1:1), top up with water to 150 cm
and the electrolysis is carried out as specified in GOST 23859.1−79.
When the mass fraction of chromium in bronze to 0.4%, the electrolyte is evaporated to a volume of 70−80 cm, transferred to a volumetric flask with a capacity of 100 cm
and up to the mark and top up with water. For the mass concentration of chromium more than 0.4% of the electrolyte transferred to a volumetric flask with a capacity of 250 cm
, and topped to the mark with water. Depending on the mass fraction of chromium taken aliquot part of the solution (see table) and placed in a beaker with a capacity of 100 cm
.
| Mass fraction of chromium, % | The volume of sample solution, cm |
The volume aliquote part of the solution, cm |
The weight of the portion corresponding to aliquote part of the solution, g |
| From 0.15 to 0.2 incl. | 100 | 20 |
0,05 |
| SV. 0,2 «0,4 « | 100 | 10 | 0,025 |
| «Of 0.4» to 0.8 « | 250 | 10 |
0,01 |
| «To 0.8» to 1.3 « | 250 | 5 | 0,005 |
The solution was evaporated to release white smoke of sulfuric acid, cooled, the salt was dissolved in 5 cmof water. Then add 20 cm
of a mixture of acids, 1 cm
of solution of nitrate of silver, 5 cm
solution naternicola ammonium solution is heated and boiled for 3−5 min prior to the complete decomposition of ammonium naternicola.
The cooled solution is transferred to a volumetric flask with a capacity of 100 cm, add water to a volume of 60 cm
, 15 cm
diphenylcarbazide solution, made up to the mark with water and mix.
Immediately measure the optical density of the solution on a photoelectrocolorimeter with a yellow green filter or on spectrophotometer at 546 nm in a cuvette with a thickness of absorbing layer 1 cm*. As a solution comparison solution is used in the reference experiment.
________________
* The text matches the original. — Note the CODE.
6.2. Construction of calibration curve
In five of the six tumblers with a capacity of 100 cmis placed 1,0; 2,0; 3,0; 4,0 and 5,0 cm
standard solution B chromium. In all the cups and add 1 cm
of sulfuric acid (1:4) and double-evaporated until a white smoke of sulfuric acid. Salt dissolved in 5 cm
of water, add 20 cm
of a mixture of acids and then do as specified in clause
As a solution comparison, using a solution not containing chromium.
Sec. 6. (Changed edition, Rev. N 2).
7. PROCESSING OF THE RESULTS
7.1. Mass fraction of chromium () in percent is calculated by the formula
where — mass fraction of chromium was found in the calibration schedule g;
— the weight of the portion of the sample corresponding to aliquote part of the solution,
7.2. Discrepancies in the results of three parallel definitions should not exceed the values permitted by the divergence (
the rate of convergence), calculated according to the formula
where — mass fraction of chromium in the alloy, %.
7.3. 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 calculated according to the formula
where — mass fraction of chromium in the alloy, %.
7.4. Control of accuracy of analysis results is carried out according to State standard samples of heat-resistant (CR) bronze in accordance with GOST 25086−87.
Sec. 7. (Changed edition, Rev. N 2).
