GOST 15027.12-77
GOST 15027.12−77 Bronze without tin. Methods for determination of zinc (with Amendments No. 1, 2)
GOST 15027.12−77
Group B59
INTERSTATE STANDARD
BRONZE WITHOUT TIN
Methods for determination of zinc
Non-tin bronze.
Methods for the determination of zinc
AXTU 1709
Date of introduction 1979−01−01
INFORMATION DATA
1. DEVELOPED AND INTRODUCED by the Ministry of nonferrous metallurgy of the USSR
2. APPROVED AND promulgated by the Decree of the State Committee of standards of Ministerial Council of the USSR from 20.06.77* N 1614
______________
* Probably, the error of the original. Should read
3. REPLACE GOST 15027.12−69
4. The standard fully complies ST SEV 1529−79
5. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS
| The designation of the reference document referenced |
Section number, paragraph, sub-paragraph |
| GOST 61−75 |
3.2 |
| GOST 493−79 |
Chapeau |
| GOST 614−97 |
Chapeau |
| GOST 1277−75 |
2.2, 3.2 |
| GOST 2062−77 |
2.2, 3.2 |
| GOST 3118−77 |
2.2, 3.2, 4.2 |
| GOST 3640−94 |
3.2, 4.2 |
| GOST 3760−79 |
2.2, 3.2 |
| GOST 3773−72 |
2.2 |
| GOST 4103−82 |
2.2 |
| GOST 4109−79 |
2.2, 3.2 |
| GOST 4139−75 |
2.2, 3.2 |
| GOST 4204−77 |
2.2, 3.2, 4.2 |
| GOST 4207−75 |
2.2, 3.2 |
| GOST 4233−77 |
2.2, 3.2 |
| GOST 4461−77 |
3.2, 4.2 |
| GOST 4658−73 |
2.2 |
| GOST 6563−75 |
2.2 |
| GOST 9293−74 |
2.2, 3.2 |
| GOST 10484−78 |
2.2, 4.2 |
| GOST 19652−73 |
3.2 |
| GOST 11125−84 |
2.2 |
| GOST 11293−89 |
2.2 |
| GOST 14261−77 |
2.2, 3.2 |
| GOST 15027.1−77 |
2.4.2 |
| GOST 18175−78 |
Chapeau |
| GOST 20301−74 |
2.2, 3.2 |
| GOST 25086−87 |
1.2, 2.5.2 b, 3.5.4, 4.4.4 |
| THAT 6−09−4327−78 |
2.2 |
| THAT 6−09−5413−88 |
3.2 |
| THAT 113−08−586−86 |
3.2 |
6. Limitation of actions taken by Protocol No. 3−93 Interstate Council for standardization, Metrology and certification (ICS 5−6-93)
7. EDITION with Amendments No. 1, 2 approved in February 1983, March 1988 (IUS 6−83, 6−88)
This standard sets the polarographic method for the determination of zinc (at a mass fraction of zinc from 0.01% to 2%), titrimetric method for the determination of zinc (at a mass fraction of zinc from 0.2% to 2%) and atomic absorption method for the determination of zinc (at a mass fraction of zinc from 0.01% to 10%) according to GOST 18175, GOST and GOST 614 493.
(Changed edition, Rev. N 1, 2).
1. GENERAL REQUIREMENTS
1.1. General requirements for methods of analysis GOST 25086 with the addition of sec. 1 GOST 15027.1.
(Changed edition, Rev. N 1, 2).
2. POLAROGRAPHIC METHOD FOR DETERMINING ZINC
2.1. The essence of the method
The method is based on the polarographic determination of zinc on the background chloridemolecular buffer solution after the chromatographic and electrolytic separation of copper.
2.2. Apparatus, reagents and solutions
Installation for electrolysis with platinum electrodes according to GOST 6563.
A chromatographic column made of glass, a height of 600 mm and a diameter of 15 mm (see drawing).
Polarography oscillographic-type-5122, polarograph type PPT-1 or any other suitable polarograph AC.
The polarographic cell, made of glass, with a capacity of not less than 40 cm, with an external reference electrode (saturated calomel electrode) and mercury-drip cathode.
Ion-exchange resin AV-17 GOST 20301.
Wool glass.
Nitrogen gas according to GOST 9293.
Sulfuric acid according to GOST 4204, diluted 1:1.
Nitric acid according to GOST 11125 and diluted 1:1.
Hydrochloric acid according to GOST 14261, solution 2 mol/ldiluted 1:1, and 3% solution.
The mixture of acids to dissolve; prepared by mixing one volume of concentrated nitric acid with three volumes of concentrated hydrochloric acid.
Sodium chloride according to GOST 4233, saturated solution.
The hydroxide of potassium (caustic potash) solution 50 and 100 g/DM.
Silver nitrate according to GOST 1277, a solution of 10 g/DM.
Potassium ferrocyanide according to GOST 4207, a solution of 30 g/DM.
Hydrofluoric acid according to GOST 10484.
Bromatologia acid according to GOST 2062.
Bromine according to GOST 4109.
Mix to dissolve, freshly prepared; prepared as follows: nine volumes bromatological acid is mixed with one volume of bromine.
Sodium sanitarily crystal on the other 6−09−4327.
Gelatin GOST 11293.
Ammonium chloride according to GOST 3773.
Ammonia water according to GOST 3760.
Potassium rodanistye according to GOST 4139, a solution of 10 g/DM.
Mercury GOST 4658 stamps r0, dehydrated.
Background electrolyte; is prepared in the following way: 53 g of ammonium chloride and 25 g semitecolo sodium dissolved in 500 cmof water; 0.2 g of gelatine are dissolved in 50 cm
of hot water. After cooling, combine the two solutions, add 75 cm
of ammonia and add water to 1 DM
.
Zinc brand of C0 according to GOST 3640.
The zinc standard solution; is prepared as follows: 0.1 g of zinc was dissolved with heating in 30 cmof hydrochloric acid diluted 1:1. The solution is transferred into a measuring flask with volume capacity of 1000 cm
, made up to the mark with water and mix. 1 cm
of the solution contains 0.0001 g of zinc.
Ammonium radamisty, a solution of 10 g/DM.
(Revised edition, Edit
. N 1).
2.3. Preparation for assay
2.3.1. Preparation of chromatographic columns to work
50 g of the ion exchange resin fractions of 0.25−0.5 mm were placed in a glass with a capacity of 500 cmand 40 cm pour
sodium chloride solution. The resin is kept in solution for 24 hours at room temperature. The solution is drained and the resin was washed by decantation with 3% hydrochloric acid to remove iron (reaction with potassium thiocyanate or ammonium). The resin was sequentially washed with a solution of potassium hydroxide 50 g/DM
, and then with a solution of 100 g/DM
the complete removal of chloride ions (reaction with silver nitrate). The resin was washed with distilled water until a weakly alkaline reaction wash liquid, then treated with three portions of solution of 2 mol/DM
of hydrochloric acid in 100 cm
each.
In the lower part of the ion-exchange column is placed a pad of glass wool, then fill the column with a layer of resin with a height of 30−32 cm, while carefully monitored to ensure that air bubbles did not stay between the grains of resin. After filling the column through the resin flow 100 cmof solution of 2 mol/DM
of hydrochloric acid.
Before analysis the height of the hydrochloric acid solution over the resin should be 1 to 2 cm.
In the process, the chromatographic column should remain under the liquid layer height of not less than 2 cm.
After chromatographic separation resin regeniriruyut by washing with water until slightly acidic wash liquid, and then 100 cmof solution of 2 mol/DM
of hydrochloric acid.
2.4. Analysis
2.4.1. With chromatographic separation of copper
The weight of bronze (PL.1) is placed in a beaker with a capacity of 250 cm, covered with watch glass, and dissolved by heating in 20 cm
of the mixture of acids to dissolve.
Table 1
| Mass fraction of zinc, % | The mass of charge, g | Aliquota part of the solution, taken on polarography, cm |
| From 0.001 to 0.05 |
1 | 20 |
| SV. Of 0.05 «to 0.2 |
0,5 | 10 |
| «0,2» 0,5 |
0,2 | 5 |
| «0,5» 1,0 |
0,1 | 5 |
| «1,0» 2,0 |
0,1 | 2 |
After the dissolution of the glass and the side of the Cup washed with water, the solution was evaporated to dryness, the dry residue dissolved in 10 cmof concentrated hydrochloric acid and again evaporated to dryness. Treatment of dry residue with hydrochloric acid is repeated four times.
The dry residue is dissolved in 40 cmof solution of 2 mol/DM
of hydrochloric acid and pass the solution through a chromatographic column with ion-exchange resin at a speed of 2 cm
/min. bandwidth of the solution is regulated by a valve or clamp at the bottom of the column. After passing the sample the column was washed with a solution of 2 mol/DM
of hydrochloric acid until complete washing from copper (the lack of reaction of the eluate with ferrocyanide of potassium).
Zinc desorbent 250 cmof water at a rate of 1.5−2 cm
/min, collecting the eluate in a glass with a capacity of 300 cm
.
The solution was evaporated to wet salts, the salts dissolve in low heat in the background electrolyte and transferred to a volumetric flask with a capacity of 100 cm, made up to the mark with the same solution and mix.
Simultaneously with the determination of zinc in bronze spend control experience with all reagents as described above.
In a polarographic cell is placed aliquot part of the solution (see table.1), diluted with background electrolyte of 20 cm, rinsed with nitrogen flow for 3−5 min and remove the cathodic polarization curve in the voltage range from minus 1.0 to minus 1.6, registering a peak recovery of zinc at minus 1.35 V.
When working with polarography DC solution add 2−3 crystals of sodium semitecolo.
The sensitivity of the recording instrument is selected so that the height of the peak of zinc was at least 10 mm.
When working with polarograph type-5122 determination is carried out at a scanning speed of 0.5−1 V/s, in the modes «differential.1» or «differential.2».
The zinc content in the solution find by the method of standard additions. Aliquot part of the standard zinc solution is added to the solution, stirred for 3 min and further analysis are as under determination of zinc in the alloy.
The volume of standard addition are selected so that the peak height of zinc increased 1.5−2 times compared to the peak height of zinc in the analyzed solution.
(Changed edition, Rev. N
1).
2.4.2. The electrolytic separation of copper
Weighed bronze (see table.1) is placed in a beaker with a capacity of 300 cm, covered with watch glass and dissolved in 15 cm.
of nitric acid diluted 1:1, when heated. Upon dissolution of the glass and rinse walls of beaker with water, the solution was boiled to remove oxides of nitrogen, cooled, diluted with water to 150 cm
, add 3 cm
of sulphuric acid, and electrolysis is carried out according to GOST 15027.1. The solution after electrolysis was evaporated to wet salts, the salts dissolve in low heat in a chloride-ammonia buffer solution, and then carry out the analysis as described in section
2.4.3. In the analysis of alloys with a mass fraction of silicon in excess of 0.05% of weighed bronze (see table.1) is placed in a platinum Cup and dissolved in 20 cmof nitric acid, diluted 1:1, and 2 cm
hydrofluoric acid. After dissolution, add 20 cm
of sulphuric acid diluted 1:1, evaporated to a thick smoke of sulfuric acid. Cooled, the walls of the Cup then rinsed with water and evaporated to dryness. The residue is dissolved in 50−70 cm
of 2 mol/DM
of hydrochloric acid and then act as described in claim
2.4.4. In the analysis of alloys with a mass fraction of tin and of lead more than 0.05% of weighed bronze (see table.1) is placed in a beaker with a capacity of 250 cm, cautiously add 20 cm
of the mixture for dissolution. After dissolution of the sample solution cautiously evaporated to dryness. Evaporation with 15 cm
of the mixture to dissolve, repeat 3−4 times to complete the Stripping of tin, to the residue add 10 cm
sulphuric acid diluted 1:1, evaporated to a thick smoke of sulfuric acid. Cool, rinse walls of beaker with water and again evaporated to a thick smoke of sulfuric acid. Cool, add 30 cm
of water, heated to boiling, cooled and filtered through a dense filter, washed the filter cake with sulfuric acid, dilute 3:100. The filtrate was evaporated to dryness, the dry residue is dissolved in 50−70 cm
of hydrochloric acid and then act as described in claim
2.4.3,
2.5. Processing of the results
2.5.1. Mass fraction of zinc () in percent is calculated by the formula
where is the peak height of zinc in polarography the test solution, mm;
— the height of the peak of zinc in polarography control solution, mm;
— the concentration of a standard solution of zinc, g/cm
;
— the volume of standard addition, cm
;
— the height of the peak of the zinc after the introduction of standard solution, mm;
— the weight of the portion of alloy, suitable aliquote part of the solution, taken on polarography,
G.
2.5.2. The absolute discrepancies in the results of parallel measurements (the rate of convergence) must not exceed the permissible values given in table.2.
Table 2
| Mass fraction of zinc, % |
|
|
| From 0.01 to 0.05 |
0,005 | 0,01 |
| SV. 0,05 «0,10 |
0,01 | 0,02 |
| «To 0.10» to 0.25 |
0,015 | 0,04 |
| «0,25» 0,50 |
0,03 | 0,07 |
| «To 0.50» for 1.5 |
0,04 | 0,1 |
| «To 1.5» 3 |
0,07 | 0,2 |
| «3» 5 |
0,10 | 0,2 |
| «5» 10 |
0,12 | 0,3 |
(Changed edition, Rev. N 2).
2.5.2. The absolute discrepancies of the analysis results 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 table.2.
2.5.2 b. Control of accuracy of analysis results
Control of accuracy of analysis results is carried out by additives or by comparing the analysis results obtained by polarographic and atomic absorption methods in accordance with GOST 25086.
2.5.2 a, 2.5.2 b. (Added, Rev. N 2).
2.5.3. The differences in the assessment of the quality of bronze used polarographic method.
3. TITRIMETRIC CHELATOMETRIC METHOD FOR THE DETERMINATION OF ZINC
3.1. The essence of the method
The method is based on complexometric titration of zinc in the eluate after pre-separation by ion exchange chromatography on anion exchanger an-31 in chloroform.
3.2. Apparatus, reagents and solutions
Glass column, filled with anion exchange resin (as a column, you can use a burette with a capacity of 50 cm, with a diameter of 12−15 mm).
Anion exchange resin an-31 according to GOST 20301.
Hydrochloric acid according to GOST 3118 and the solution, diluted 1:1, 1:20, solutions 2 and 0.03 mol/DM.
Nitric acid according to GOST 4461.
A mixture of nitric and hydrochloric acids, 1:3, freshly prepared.
Sulfuric acid according to GOST 4204, solution 1 mol/DM.
Ammonia water according to GOST 3760 and diluted 1:5.
Acetic acid according to GOST 61.
Buffer solution (pH 5,7); is prepared as follows: 48 cmof acetic acid and 58 cm
of ammonia diluted with water to 500 cm
.
Selenology orange.
Sodium chloride according to GOST 4233 and a saturated solution.
The mixture kylinalove orange with sodium chloride 1:100, well pounded.
Potassium rodanistye according to GOST 4139, a solution of 10 g/DM.
Silver nitrate according to GOST 1277, a solution of 10 g/DM.
Potassium ferrocyanide according to GOST 4207, a solution of 30 g/DM.
Sodium hydroxide according to GOST 4328, solution 50 and 100 g/DM.
Zinc GOST 3640, brand C0.
The zinc standard solution; is prepared as follows: 1 g of zinc is dissolved in 25 cmof hydrochloric acid diluted 1:1, the solution was evaporated to dryness, the dry residue dissolved in 100 cm
of hydrochloric acid diluted 1:1, transferred to a volumetric flask with a capacity of 1 DM
and made up to the mark.
1 cmof the solution contains 0.001 g of zinc.
Salt is the disodium Ethylenediamine-N, N, N', N'-tetraoxane acid 2-water (Trilon B) according to GOST 10652, solution 0,01 mol/DM.
Sulfuric acid according to GOST 4204, diluted 1:1 and 3:100.
Bromatologia acid according to GOST 2062.
Bromine according to GOST 4109.
The mixture for dissolving freshly prepared; prepared as follows: nine volumes bromatological acid is mixed with one volume of bromine.
Sodium fluoride, on the other 113−08−586, a solution of 100 g/DM.
Sodium Chernovetskiy on the other 6−09−5413.
(Amended,
Izm. N 1).
3.3. Preparation for assay
3.3.1. Preparation of chromatographic columns to work
50 g of anion exchange resin (fine fraction) was placed in a beaker with capacity of 500 cmand pour 400 cm
of saturated sodium chloride solution. The resin is kept in solution for 24 hours at room temperature. The solution is decanted and the resin was washed by decantation with hydrochloric acid diluted 1:20 to complete the removal of iron (reaction with potassium thiocyanate). The resin was sequentially washed with a solution of sodium hydroxide 50 g/DM
, and then with a solution of 100 g/DM
the complete removal of the chloride ion (reaction with silver nitrate). The resin was washed with water until a weakly alkaline reaction wash liquid, then treated with three portions of solution of 2 mol/DM
of hydrochloric acid in 100 cm
each.
In the lower part of ion exchange columns is placed a pad of glass wool, then fill the column with a resin height of 30−32 cm, while carefully monitored to ensure that air bubbles did not stay between the grains of resin. After filling the column through the resin flow 100 cmof solution of 2 mol/DM
of hydrochloric acid.
Before analysis the height of the hydrochloric acid solution over the resin should be 1 to 2 cm.
At the end of the chromatographic separation resin is regenerated by flushing with water until slightly acidic wash liquid, and then 100 cmof solution of 2 mol/DM
hydrochloric sour
comes.
3.3.2. The installation of the titer of the solution Trilon B
25 cmstandard solution of zinc was evaporated to dryness, add 50 cm
of solution of 2 mol/DM
of hydrochloric acid, heated to dissolve the salts, is cooled and passed through the column at a rate of 5 cm
/min, Then elute the zinc with a solution of 0.03 mol/DM
of hydrochloric acid and titrated as described in section 3.3.
The titer of the solution Trilon B (), expressed in grams of zinc on 1 cm
of a solution, calculated by the formula
where is the mass of zinc, taken for titration, g;
— volume of solution Trilon B, spent on titration, sm
.
3.4. Analysis
3.4.1. For alloys with a mass fraction of tin and lead, less than 0.05%
Weighed bronze (see table.3) is placed in a beaker with a capacity of 300 cm, cover with a watch glass, and dissolved in 20 cm
of a mixture of acids when heated, and evaporation to dryness. To the residue was added 10 cm
of concentrated hydrochloric acid and repeat the evaporation for three times to remove nitric acid, adding each time 10 cm
of hydrochloric acid. Chilled dry residue is dissolved in 50 cm
solution of 2 mol/DM
hydrochloric acid when heated.
Table 3
| Mass fraction of zinc, % |
The mass of charge, g |
| From 0.2 to 1.0 |
1 |
| SV. 1,0 «2,0 |
0,5 |
The solution passed through the column at a rate of 5 cm/min. Glass column and washed with 200 cm
with a solution of 2 mol/DM
hydrochloric acid at the same rate until complete removal of copper ions. Control for completeness of washing is carried out with a solution of ferrocyanide of potassium. Zinc eluted in 250 cm
of solution of 0.03 mol/DM
of hydrochloric acid, while maintaining the same flow velocity. The eluate is collected in a conical flask with a capacity of 500 cm
, pour a pinch of orange xrenovo mixture with sodium chloride to light yellow color of the solution and neutralized with ammonia solution diluted 1:5, drop by drop before moving to the slightly purple color, add 2.5 cm
of a solution of sodium servational and 1 cm
of a solution of sodium fluoride.
Pour 10 cmof buffer solution and titrated with a solution of Trilon B till the transition of color from light lavender to light lemon.
(Changed edition, Rev. N
1).
3.4.2. For alloys with a mass fraction of tin and lead, more than 0,05%
Weighed bronze (see table.3) is placed in a beaker with a capacity of 250 cmand carefully add 20 cm
of the mixture for dissolution. After dissolving, the solution was evaporated to dryness. Evaporation with 15 cm
of the mixture to dissolve, repeat 3−4 times. To the residue add 10 cm
sulphuric acid diluted 1:1, evaporated to a thick white smoke of sulfuric acid, cooled, rinse the walls of the glass with water and again evaporated to dense white smoke of sulfuric acid. Cool, add 50 cm
of water, boil to dissolve the salt, cooled and allowed to stand for 4 h, filter the precipitate on a tight filter, washing it with a solution of sulfuric acid, dilute 3:100.
The filtrate was evaporated to dryness, the residue dissolved in 50−70 cmof 2 mol/DM
of hydrochloric acid and then act as described in paragraph
(Changed edition, Rev. N 1)
.
3.5. Processing of the results
3.5.1. Mass fraction of zinc () in percent is calculated by the formula
where — volume of solution Trilon B, spent on titration, sm
;
the titer of the solution Trilon B, expressed in grams of zinc on 1 cm
;
— the weight of the portion,
3.5.2. The absolute discrepancies in the results of parallel measurements (the rate of convergence) must not exceed the permissible values given in table.2.
(Changed edition, Rev. N 2).
3.5.3. The absolute discrepancies of the analysis results 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 table.2.
3.5.4. Control of accuracy of analysis results
Control of accuracy of analysis results is carried out by additives or by comparing the results obtained with titrimetric and atomic absorption methods in accordance with GOST 25086.
3.5.3,
4. ATOMIC ABSORPTION METHOD FOR DETERMINING ZINC
4.1. The essence of the method
The method is based on measuring the absorption of light by atoms of zinc, formed by the introduction of the analyzed solution in the flame acetylene-air.
4.2. Apparatus, reagents and solutions
Atomic absorption spectrometer with a radiation source for zinc.
Nitric acid according to GOST 4461 and diluted 1:1.
Hydrochloric acid according to GOST 3118 and diluted 1:1 and solutions 2 and 1 mol/DM.
A mixture of acids, is prepared as follows: the amount of nitric acid mixed with three volumes of hydrochloric acid.
Hydrofluoric acid according to GOST 10484.
Sulfuric acid according to GOST 4204, diluted 1:1.
Zinc GOST 3640 with a mass fraction of zinc not less than 99.9%.
Standard solutions of zinc.
Solution A, prepared as follows: 0.5 g of zinc is dissolved by heating in 20 cmof hydrochloric acid diluted 1:1, the solution was cooled, transferred to a measuring flask with volume capacity of 1000 cm
and top up with water to the mark.
1 cmof the solution contains 0.0005 g of zinc.
Solution B is prepared as follows: 20 cmsolution And transferred to a volumetric flask with a capacity of 100 cm
, add 10 cm
solution of 2 mol/DM
of hydrochloric acid and add water to the mark.
1 cmof a solution contains 0.0001 g of zinc.
Solution; prepared as follows: 10 cmof a solution transferred to a volumetric flask with a capacity of 100 cm
, add 10 cm
solution of 2 mol/DM
of hydrochloric acid and add water to the mark.
1 cmof the solution contains 0,00001
g zinc.
4.3. Analysis
4.3.1. For bronzes with a mass fraction of tin and silicon up to 0.05%
A portion of the bronze mass, given in table.5, is placed in a beaker with a capacity of 250 cmand dissolved by heating in 10 cm
of nitric acid, diluted 1:1.
Table 5
| Mass fraction of zinc, % | The mass of charge, g | The volume of sample solution, cm |
The volume aliquote part of the solution, cm |
The volume of 2 mol/DM |
The volume of sample solution after dilution, see |
| From 0.01 to 0.1 |
1 | 100 | The entire solution |
- | - |
| SV. 0,1 «0,5 |
1 | 100 | 10 | 10 | 100 |
| «Of 0.5» to 4.0 |
0,5 | 250 | 5 | 10 | 100 |
| «A 4.0» 10 |
0,5 | 250 | 5 | 25 | 250 |
The solution was cooled, transferred to an appropriate volumetric flask (see table 5) and then filled to the mark with water. Aliquot part of the solution transferred to an appropriate volumetric flask, add a solution of 2 mol/DMof hydrochloric acid and add water to the mark.
Measure the atomic absorption of zinc in the flame of acetylene-air at a wavelength of 213,8 nm parallel to the calibration solutions.
4.3.2. For bronzes with a mass fraction of tin in excess of 0.05%
A portion of the alloy mass, given in table.5, is placed in a beaker with a capacity of 250 cmand dissolved by heating in 10 cm
of a mixture of acids. The solution was cooled, transferred to an appropriate volumetric flask (see table 5) rinse walls of beaker with a solution of 1 mol/DM
of hydrochloric acid and add water up to the mark with the same acid. Aliquot part of the solution transferred to an appropriate volumetric flask (see table 5) and then filled to the mark with a solution of 1 mol/DM
of hydrochloric acid.
Measure the atomic absorption of zinc, as specified in clause
(Changed edition, Rev. N 2).
4.3.3. For bronzes with a mass fraction of silicon in excess of 0.05%
A portion of the bronze mass, given in table.5, is placed in a platinum Cup and dissolved by heating in 10 cmof nitric acid, diluted 1:1, and 2 cm
hydrofluoric acid. After dissolution, add 10 cm
sulphuric acid diluted 1:1, and the solution was evaporated until a white smoke of sulfuric acid. The residue is cooled, rinse the walls of the Cup with water and evaporated again until a white smoke of sulfuric acid. The residue is cooled and dissolved in water when heated. The solution was cooled, transferred to an appropriate volumetric flask (see table 5) and then filled to the mark with water. Aliquot part of the solution transferred to an appropriate volumetric flask (see table 5), a solution of 2 mol/DM
of hydrochloric acid and add water to the mark.
Measure the atomic absorption of zinc, as specified in clause
4.3.4. Construction of calibration curve
Ten of the eleven volumetric flasks with a capacity of 100 cmis placed 2,5; 5,0; 10 cm
standard solution Into; 1,5; 2,0; 2,5; 3,0; 4,0; 5,0; 6,0 cm
standard solution of zinc. To all flasks add 10 cm
solution of 2 mol/DM
of hydrochloric acid and add water to the mark.
Measure the atomic absorption of zinc, as specified in clause
According to the obtained results build a calibration curve.
4.4. Processing of the results
4.4.1. Mass fraction of zinc () in percent is calculated by the formula
where — concentration of zinc was found in the calibration schedule, g/cm
;
— the volume of the final sample solution, cm
;
— the weight of the portion contained in the final volume of the sample solution,
4.4.2. The absolute discrepancies in the results of parallel measurements (the rate of convergence) must not exceed the permissible values given in table.2.
(Changed edition, Rev. N 2).
4.4.3. The absolute discrepancies of the analysis results obtained in two different laboratories or two of the results of the analysis conducted in the same laboratory but under different conditions (a measure of reproducibility) shall not exceed the values given in table.2.
4.4.4. Control of accuracy of analysis results
Control of accuracy of analysis results is carried out by additives or by comparison of the results obtained by atomic absorption and titrimetric or polarographic methods in accordance with GOST 25086.
4.4.3,
