GOST 12354-81
GOST 12354−81 Steel alloyed and high alloy. Methods for determination of molybdenum (Change No. 1)
GOST 12354−81
Group B39
INTERSTATE STANDARD
STEEL ALLOYED AND HIGH-ALLOYED
Methods for determination of molybdenum
Steels alloyed and highalloyеd.
Methods for the determination of molybdenum
Date of introduction 1981−06−01
APPROVED AND put INTO EFFECT by Decision of the USSR State Committee for standards from
REPLACE GOST 12354−66 in part of sec. 2−4
Limitation of actions taken by Protocol No. 2−92 of the Interstate Council for standardization, Metrology and certification (ICS 2−93)
The re-release (Feb 1999) with amendment No. 1, approved in December 1985 (IUS 4−86).
This standard establishes photometric with extraction (when the mass fraction of from 0.01 to 3.0%), photometric extraction without (with mass fraction from 0.1 to 10.0%), gravimetric (for the mass concentration of from 3.0 to 10.0%) and atomic absorption (at a mass fraction of from 0.01 to 5.0%) methods for determination of molybdenum in alloy steels and high alloy steels.
The standard complies ST SEV 963−78 in part of sec. 2, 4, 5.
(Changed edition, Rev. N 1).
1. GENERAL REQUIREMENTS
1.1. General requirements for methods of analysis GOST 28473−90.
2. THE PHOTOMETRIC METHOD FOR THE DETERMINATION OF MOLYBDENUM BY EXTRACTION
2.1. The essence of the method
The method is based on the formation of complex compounds of molybdenum (V) with romanisti ammonia, extraction his -butyl acetate and measuring the light absorption of the obtained colored extract at a wavelength of 470 nm. Molybdenum (VI) and iron (III) is reduced to molybdenum (V) and iron (II) ascorbic acid in the presence of copper sulphate. Tungsten, vanadium and titanium transferred to the complexes of citric acid and disodium salt of ethylenediaminetetraacetic acid.
2.2. Equipment and reagents
Spectrophotometer or photoelectrocolorimeter.
A mixture of acids: 500 cmof water 150 cm
of phosphoric acid and 350 cm
of perchloric acid carefully mixed.
Hydrochloric acid by the GOST 3118−77 or GOST 14261−77 and diluted 1:1.
Nitric acid GOST 4461−77 or GOST 11125−84 and diluted 1:4.
Sulfuric acid GOST 4204−77 or GOST 14262−78 and diluted 1:1.
Perchloric acid, a solution of 570 g/DM.
Orthophosphoric acid according to GOST 6552−80.
Citric acid according to GOST 3652−69, a solution of 200 g/DM.
Ascorbic acid, a solution of 30 g/DM.
Ammonia water according to GOST 3760−79.
Disodium salt of ethylenediaminetetraacetic acid (EDTA) according to GOST 10652−73, a solution of 20 g/DM.
Copper sulfate according to GOST 4165−78, a solution of 0.3 g/DM.
-The butyl acetate according to GOST 22300−76.
Ammonium radamisty according to GOST 19522−74, a solution of 300 g/DM.
Tin chloride according to NTD, a freshly prepared solution of 100 g of tin chloride dissolved in 100 cmof hot hydrochloric acid. The solution is cooled, add two granules of metallic tin and add water to 1 DM
.
Sodium volframovich 2-water according to GOST 18289−78.
Iron ferrous sulfate according to GOST 4148−78.
Solution volframovich sodium and ferrous iron sulfate: 2 g volframovich of sodium and 45 g of ferrous sulphate of iron is dissolved in a small amount of water, add 30 cmof sulphuric acid (1:1), 5 cm
of nitric acid and evaporated to fumes of sulfuric acid. The solution was cooled, the side of the Cup washed with water and again evaporated to fumes of sulfuric acid. A glass with the contents cool, cautiously add 100 cm
of solution of citric acid and add ammonia to pH 7−8 by universal indicator. Then pour 10 cm
of ammonia and the solution was heated until complete dissolution of the precipitate tungsten acid. After cooling, the solution is neutralized with sulfuric acid (1:1) and add 10 cm
in excess. The solution was transferred to a volumetric flask with a capacity of 500 cm
, made up to the mark with water and mix.
Radio engineering carbonyl iron according to GOST 13610−79 or GSO-1, iron net type 008 ZHR.
Universal indicator paper.
Lead acetate according to GOST 1027−67, a solution of 20 g/DM.
Ammonium nitrate according to GOST 22867−77, a solution of 25 g/DM.
Ammonium acetate according to GOST 3117−78, a solution of 500 g/DM.
Ammonium molybdate according to GOST 3765−78.
Recrystallization of ammonium molybdate in 250 g of reagent was dissolved in 490 cmof water when heated to 70−80 °C, cautiously add ammonia until a clear smell. The solution was filtered through filter «blue ribbon», is cooled to 20−25 °C and poured under stirring in 300 cm
of ethyl alcohol. Sediment is allowed to settle for 1 h and filtered, the filter «white ribbon» placed in a Buchner funnel, using a water vacuum pump. Precipitate was washed 2−3 times with ethanol and dried.
Molybdenum metal brand MCIT.
Standard solutions of molybdenum.
Solution a: 4,6005 g svejeprigotovlennogo and dried at 105 °C ammonium molybdate was placed in a beaker and dissolved in water when heated. After cooling, the solution is transferred to a volumetric flask with a capacity of 1 DM, made up to the mark with water and mix.
The mass concentration of a standard solution And establish the gravimetric method: to do this, 40 cmof a standard solution of ammonium molybdate And placed in a beaker with a capacity of 400 cm
, pour 2 cm
of hydrochloric acid (1:1), 25 cm
of a solution of acetate of ammonium, and dilute with water to 200 cm
. The solution is heated to boiling and poured dropwise 25 cm
of a solution of acetate of lead. The contents of the beaker are boiled under stirring for 10−15 min.
Solution and the precipitate was left for 12 hours, then the precipitate is filtered on two filters «blue» and «white ribbon» and washed 8−10 times with hot ammonium nitrate solution.
The filter with precipitate was placed in a calcined to constant weight and weighed porcelain crucible, dried, incinerated, and calcined at 500−600°C to constant weight, cooled in a desiccator and weighed.
Simultaneously conduct control experience for contamination of reagents.
The mass concentration of molybdate ammonium solution , expressed in g/cm
of molybdenum, calculated by the formula
where is the mass of the crucible with the precipitate of lead molybdate, g;
— weight of crucible without the precipitate of lead molybdate, g;
— the mass of the crucible with the sediment in a control experiment, g;
— weight of crucible without the sediment in a control experiment, g;
0,2613 — the conversion factor of lead molybdate to molybdenum;the volume of the solution of ammonium molybdate, taken for installation of the mass concentration, cm
.
1 cmof a standard solution And must contain 0.0025 g of molybdenum.
Solution B: 200 cmstandard solution And 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 B of metallic molybdenum. For this, 0.5 g of molybdenum metal are dissolved in 20 cmof nitric acid (1:4) and 5 cm
of sulfuric acid. The solution was evaporated to sulphuric acid fumes, cooled and dissolved salts when heated in 100 cm
of water.
The solution was transferred to a volumetric flask with a capacity of 1 DM, cooled, made up to the mark with water and mix.
1 cmstandard solution B contains 0.0005 g of molybdenum.
(Redrafted From
M. N 1).
2.3. Analysis
2.3.1. The weight of steel depending on the mass fraction of molybdenum is determined by the table.1.
Table 1
| Mass fraction of molybdenum, % |
The weight of steel, g |
Aliquota part of the solution, see |
| From 0.01 to 0.10 |
1 | 50,0 |
| SV, of 0.10 «to 0.25 |
1 | 25,0 |
| «0,25» 0,50 |
0,5 | 25,0 |
| «To 0.50» of 1.30 |
0,2 | 25,0 |
| «1,30» of 3.00 |
0,2 | 10,0 |
The sample is placed in a steel Cup with a capacity of 100−250 cmand dissolved by heating in 20 cm
of a mixture of perchloric and phosphoric acids. If the steel is not soluble in the mixture of perchloric and phosphoric acids, the sample was dissolved in 20−30 cm
of hydrochloric acid, oxidize 2−3 cm
of nitric acid and add 20 cm
of perchloric and phosphoric acids. The solution was evaporated until the appearance of dense fumes of perchloric acid, cooled and dissolved salts when heated to 80−100 cm
of water. The solution was cooled, transferred to a volumetric flask with a capacity of 250 cm
, made up to the mark with water and mix.
In the analysis of steels in which the content of tungsten to molybdenum content less than 8, and containing vanadium and titanium, aliquot part of the solution (table. 1) was transferred to a beaker with a capacity of 100 cm, add 10 cm
of EDTA, boiled and, after cooling, transferred to a separatory funnel with a capacity of 150−200 cm
.
If a the content of tungsten to molybdenum content equal to or more than 8, the sample is placed in a steel Cup with a capacity of 600 cm, dissolved in 20 cm
of hydrochloric acid, oxidize 2−3 cm
of nitric acid and add 15 cm
of sulphuric acid (1:1). The solution was evaporated until the appearance of sulphuric acid fumes and cooled, pour 100 cm
of citric acid and stirred. Then add ammonia to pH 7−8 (control by universal indicator), add another 10 cm
of ammonia and heated to complete dissolution of the precipitate tungsten acid.
The solution was cooled, was added sulfuric acid (1:1) to pH 7−8 (control by universal indicator) and poured 5 cmexcess.
The solution was transferred to a volumetric flask with a capacity of 250 cm, cooled, made up to the mark with water and mix.
Aliquot part of the solution (table. 1) is placed in a separating funnel with a capacity of 150−200 cm, flow 10 cm
of hydrochloric acid (1:1) (pH should be less than 0.5), 5 cm
of a solution of sulphate of copper and 5 cm
of the solution askor
benovoy acid.
2.3.1.1. The solution was mixed thoroughly, incubated for 3 min, poured from the burette 50cm-butyl acetate and shake. After 5 min, add 5 cm
of a solution of ammonium Rodenstock separating funnel and vigorously shaken for 1 min.
After the separation of the liquids, the aqueous layer drained and discarded. To the extract was added 10 cmof a solution of tin chloride and shaken for 1 min. the Aqueous layer is decanted and discarded and the extract is again shaken out with 3−5 cm
of a solution of chloride of tin. The aqueous layer is discarded and the light absorption of the extract measured in a spectrophotometer at a wavelength of 470 nm or photoelectrocolorimeter with a filter having maximum transmission in the wavelength range of 440−490 nm. The thickness of the light absorbing layer of the cell is chosen so to obtain a value of optical density within the linear part of calibration curve. As a comparison, using a solution of
butyl acetate. Simultaneously with the execution of the analysis carried out control experience for contamination of reagents.
From the mean values of absorbance of analyzed solutions is subtracted the average value of optical density in a control experiment. A lot of find molybdenum in the calibration schedule.
2.3.2. Construction of calibration curve
To build a calibration curve in the analysis of steels in which the content of tungsten to molybdenum content less than 8, 11 cups with a capacity of 100−250 cmis placed 0.5 g of carbonyl iron and 10 of them go consistently: 0,4; 1,0; 1,5; 2,0; 2,5; 3,0; 3,5; 4,0; 4,5 and 5.0 cm
standard solution B of molybdenum.
11 glasses poured 20 cmof the mixture of acids and heated to dissolve portions of the iron. The solutions were evaporated to dense fumes of perchloric acid, cooled, diluted with water and transferred to volumetric flasks with a capacity of 250 cm
, made up to the mark with water and mix.
Aliquote part of the solutions at 25 cmis placed in 11 beakers with a capacity of 100 cm
, is added to 10 cm
of EDTA, boiled and, after cooling, transferred to a separating funnel with a capacity of 150−200 cm
. Within each separating funnel is poured 10 cm
of hydrochloric acid (1:1), 5 cm
of a solution of sulphate of copper, 5 cm
of ascorbic acid solution and then act as described in section
When measuring light absorption in a solution of comparison, using the extract obtained from the solution in the flask containing no molybdenum.
To build a calibration curve in the analysis of steels in which the content of tungsten to molybdenum content equal to or more than 8, 11 volumetric flasks with a capacity of 250 cmpoured in 25 cm
of a solution of tungsten and iron, and 10 of them are added successively 0,4; 1,0; 1,5; 2,0; 2,5; 3,0; 3,5; 4,0; 4,5 and 5.0 cm
standard solution B of molybdenum. The solutions were topped up to the mark with water and mix. Aliquote part of the solutions at 25 cm
11 is placed in separatory funnels with a capacity of 150−200 cm
. Within each separating funnel is poured 10 cm
of hydrochloric acid (1:1), 5 cm
of a solution of sulphate of copper, 5 cm
of ascorbic acid solution and then act as described in section
When measuring light absorption in a solution of comparison, using the extract obtained from the solution in the flask containing no molybdenum.
In the analysis of samples with a narrow range of molybdenum content allowed construction of calibration curve five points, including the determined concentration of the element.
The found values of optical density and corresponding masses of molybdenum built grabarov
full-time schedule.
2.4. Processing of the results
Mass fraction of molybdenum in percent is calculated by the formula
where is the mass of molybdenum in the sample was found in the calibration schedule g;
the weight of steel, suitable aliquote part of the solution,
2.3.1.1−2.4. (Changed edition, Rev. N 1).
3. THE PHOTOMETRIC METHOD FOR THE DETERMINATION OF MOLYBDENUM WITHOUT EXTRACTION
3.1. The essence of the method
The method is based on formation of colored complex compounds of molybdenum (V) with ammonium radamisty and measuring the light absorption of the solution at a wavelength of 470 nm. Molybdenum (VI) is reduced to molybdenum (V) with thiourea in the presence of copper sulphate. Iron, chromium, Nickel and other elements previously separated from the molybdenum oxide hydrate of sodium.
3.2. Equipment and reagents
Spectrophotometer or photoelectrocolorimeter.
Hydrochloric acid by the GOST 3118−77 or GOST 14261−77 and diluted 1:1, 1:3.
Nitric acid GOST 4461−77 or GOST 11125−84 and diluted 1:4.
Sulfuric acid GOST 4204−77 or GOST 14262−78 and diluted 1:2, 1:100, 1:4.
Hydrofluoric acid according to GOST 10484−78.
Potassium preservatory according to GOST 7172−76.
Sodium hydroxide according to GOST 4328−77, a solution of 200 g/DM.
Copper sulfate according to GOST 4165−78, a solution of 10 g/DM.
Thiourea according to GOST 6344−73, a solution of 50 g/DM.
Ammonium radamisty according to GOST 19522−74, a solution of 500 g/DM.
Ammonium citrate according to GOST dvosemyanny 3653−78, a solution of 300 g/DM.
Radio engineering carbonyl iron according to GOST 13610−79.
Iron ferrous sulfate according to GOST 4148−78.
Ammonium acetate according to GOST 3117−78, a solution of 500 g/DM.
Ammonium nitrate according to GOST 22867−77, a solution of 250 g/DM.
Lead acetate according to GOST 1027−67, a solution of 20 g/DM.
Molybdenum metal brand MCIT.
Ammonium molybdate according to GOST 3765−78, standard solution: 1.84 g ammonium molybdate svejeprigotovlennogo and dried at 105 °C is placed in a beaker and dissolved in water when heated. After cooling, the solution is transferred to a volumetric flask with a capacity of 1 DM, made up to the mark with water and mix. The mass concentration of a standard solution sets as described in section 2.2.
Allowed the preparation of a standard solution of molybdenum metal molybdenum. For this, 0.5 g of metallic molybdenum is dissolved in 5 cmof sulphuric acid and 20 cm
of nitric acid (1:4). The solution was evaporated to fumes of sulfuric acid. Cooled and dissolved salts when heated in 100 cm
of water. The solution was transferred to a volumetric flask with a capacity of 500 cm
, cooled, made up to the mark with water and mix.
1 cmof a standard solution of molybdenum must contain 0.001 g of molybdenum.
(Redrafted From
M. N 1).
3.3. Analysis
3.3.1. Steel weighed 1 g when the mass fraction of molybdenum from 0.1 to 0.8% or 0.5 g when the mass fraction of molybdenum from 0.8 to 6.0% or 0.25 g when the mass fraction of molybdenum, from 6.0 to 10.0% were placed in a glass with a capacity of 250−300 cm, 20−50 cm poured
hydrochloric acid 5−10 cm
of nitric acid and heated until complete dissolution of the sample.
Allowed other ways of dissolution of batches, ensuring complete decomposition of the sample and does not require changes in the further stage of the analysis.
The solution was cooled, poured 10 cmof sulphuric acid and evaporate to release its vapors. The solution is again cooled, the side of the Cup washed with water and again evaporated to release vapors of sulfuric acid. The contents of the beaker cooled, poured 80−100 cm
of water and heated to dissolve the salts.
The precipitate of silicic acid is filtered in two filters «white ribbon», washed 2−3 times with sulfuric acid (1:100), adding the washings to the filtrate. The resulting solution (basic) save.
The filter with precipitate was placed in a platinum crucible, dried, incinerated and calcined at 700−800 °C. the Residue in the crucible is moistened with 2−3 drops of water, add 2−3 cmof sulphuric acid (1:4), 3−5 cm
hydrofluoric acid and the contents of the crucible is evaporated until vapours of sulphuric acid. The residue in the crucible is fused with a 2−3 g peacemaking potassium, m is dissolved in 20−30 cm
of hydrochloric acid (1:3) and the solution attached to the main solution.
If the steel contains vanadium, the solution was added 2−3 g of ferrous iron sulphate.
The solution is heated to 80−90 °C and cautiously, with constant stirring, to individual portions poured into a volumetric flask with a capacity of 500 cmcontaining 100 cm
, heated to the boiling point of the solution of sodium hydroxide.
The contents of the flask are cooled, made up to the mark with water, mixed and allowed to settle sediment within 1−2 h of the solution was filtered through a dry filter into a conical flask with a capacity of 250 cm, discarding the first portions of the filtrate.
In two volumetric flasks with a capacity of 100 cmeach taken at 10 cm
is obtained and the filtrate poured into each flask 10 cm
of a solution of citrate of ammonium, 30 cm
of sulphuric acid (1:2), 2 cm
of a solution of copper sulphate and 10 cm
of a solution of thiourea. After addition of each reagent solutions in the flasks mixed. After 10 minutes, to the solution in one flask pour 4 cm
of solution Rodenstock ammonium and stirred. The solution into another flask serves as a solution comparison.
After 10 min the solutions in flasks topped up to the mark with water and mix. The optical density of the resulting solutions is measured on the spectrophotometer at a wavelength of 470 nm or photoelectrocolorimeter with a filter having maximum transmission in the wavelength range of 440−490 nm.
The thickness of the light absorbing layer of the cell is chosen so to obtain the optimal value of optical density.
The molybdenum content found by the calibration schedule. Simultaneously with the execution of the analysis carried out control and experience on pollution
e reagents.
3.3.2. Construction of calibration curve
To construct the calibration curve for the mass concentration of molybdenum from 0.1 to 1.5% in the nine of cups with a capacity of 250−300 cmis placed 1 g of carbonyl iron. In eight glasses poured 1,0; 2,0; 3,0; 4,0; 5,0; 6,0; 7,0 and 8.0 cm
of a standard solution of molybdenum. Then do as described in section
The found values of optical density and corresponding concentration of molybdenum to build the calibration graph.
To construct the calibration curve for the mass concentration of molybdenum from 1.5 to 6.0% in eight glasses with a capacity of 250−300 cmis placed 0.5 g carbonyl iron; to build a calibration curve for the mass concentration of molybdenum, from 6.0% to 10.0% in eight glasses with a capacity of 250−200 cm
is placed 0.25 g of carbonyl iron.
Seven glasses pour 8,0; 12,0; 16,0; 20,0; 24,0; 28,0; 30,0 cmstandard solution molybdenum. Then do as described in section
When measuring light absorption as a solution comparison solution is used in the eighth glass containing no molybdenum. The found values of optical density and corresponding masses of molybdenum to build the calibration graph.
3.4. Processing of the results
Mass fraction of molybdenum in percent is calculated by the formula
where is the mass of molybdenum in the sample was found in the calibration schedule g;
— the weight of the portion corresponding to aliquote part of the solution,
3.3.1−3.4. (Changed edition, Rev. N 1).
4. GRAVIMETRIC METHOD FOR THE DETERMINATION OF MOLYBDENUM
4.1. The essence of the method
The method is based on the deposition of molybdenum in the molybdate of lead, the course of annealing at 500−600°C and weighing. Molybdenum is pre-separated from iron, chromium, Nickel and other elements with sodium hydroxide or mesonoxian.
4.2. Equipment and reagents
Hydrochloric acid by the GOST 3118−77 or GOST 14261−77 and diluted 1:1, 1:3, 1:40.
Nitric acid GOST 4461−77 or GOST 11125−84.
Hydrofluoric acid according to GOST 10484−78.
Sulfuric acid GOST 4204−77 or GOST 14262−78 and diluted 1:1, 1:3, 1:4, 1:100.
Acetic acid GOST 61−75, solution 800−900 g/land diluted 1:40.
Citric acid according to GOST 3652−69.
Ascorbic acid, freshly prepared solution of 30 g/DM.
Sodium hydroxide according to GOST 4328−77, a solution of 200 r/DM.
Ammonia water according to GOST 3760−79.
Potassium preservatory according to GOST 7172−76.
The bromine water.
Copper sulfate according to GOST 4165−78, a solution of 0.3 g/DM.
Ammonium citrate according to NTD, a solution of 500 g/DM.
Iron ferrous sulfate according to GOST 4148−78.
Hydrogen peroxide according to GOST 10929−76, solution diluted 1:15.
Universal indicator paper.
Ethyl alcohol GOST 18300−87.-Benzoyloxy, ethanol solution; 20 g
-benzoyloxy dissolved in 1 DM
of ethanol and filtered.
The washing liquid (freshly prepared): 25−30 cmethanol solution
-benzoyloxy placed in a beaker with a capacity of 1 DM
, add 10 cm
sulphuric acid, mix and add water to volume of 1 DM
.
Sodium sanitarily for NTD, a solution of 200 g/DM.
Lead acetate according to GOST 1027−67, a solution of 10 g of acetate of lead dissolved in 20 cmof acetic acid, add water to 1 DM
and stirred.
Ammonium acetate according to GOST 3117−78, a solution of 500 g/DM.
Methyl red, indicator for NTD, ethanol solution of 1 g/DM.
(Amended
, Edit. N 1).
4.3. Analysis
4.3.1. In the analysis of steels containing tungsten, steel weighed 1 g when the mass fraction of molybdenum from 3 to 5% or 0.5 g when the mass fraction of molybdenum from 5 to 10% is placed in a beaker with a capacity of 250−300 cm, 30−50 cm poured
hydrochloric acid, oxidize 5−10 cm
of nitric acid and heated to dissolve sample.
Allowed other ways of dissolution of batches, ensuring complete decomposition of the sample and does not require changes in the further stage of the analysis.
The solution was evaporated to dryness, to the residue add 10 cmof hydrochloric acid and again evaporated to dryness. Operation of evaporation repeated. To the dry residue add 15−20cm
of hydrochloric acid, heated and poured 100−130 cm
of hot water.
The contents of the beaker are heated to boiling and filtered, the precipitate on the filter «white ribbon» containing filtrowanie mass. The filter residue is washed with hot hydrochloric acid (1:40) negative reaction to ions of iron. The filtrate (main) leave. The filter with precipitate was placed in a platinum crucible, dried, incinerated and burned at temperatures above 400 °C. In a crucible add 2−3 cmof sulphuric acid (1:4) and 2−3 cm
hydrofluoric acid, the crucible is heated until the termination of allocation of steams of sulfuric acid and calcined at a temperature of 400 °C. the Residue in the crucible is fused with a 2−3 g peacemaking potassium.
The melt is cooled, dissolved in 20−30 cmof hot hydrochloric acid (1:3). The solution was filtered through a filter «white ribbon», the filter was washed 2−3 times with hot water and the filtrate obtained is attached to the main filter
Tu.
4.3.2. In the analysis of steels containing tungsten, steel weighed 1 g when the mass fraction of molybdenum from 3 to 5% or 0.5 g when the mass fraction of molybdenum from 5 to 10% is placed in a beaker with a capacity of 400 cm, pour 30−50 cm
of hydrochloric acid (1:1), oxidized 5−10 cm
of nitric acid and dissolved by heating. The solution was boiled down to 2/3 the original volume, poured 100 cm
of hot water and filtered through filter «white ribbon» with the addition filtrowanie mass. The filter residue (A) washed several times with hot hydrochloric acid (1:40). The filtrate was evaporated to dryness, add 10 cm
of hydrochloric acid and again evaporated to dryness, the evaporation operation is repeated. To the dry residue in the glass poured 20 cm
of hydrochloric acid and 100 cm
of hot water. The solution is heated to boiling and filtered through the filter «white ribbon» with the addition filtrowanie mass. The filter with the precipitate (B) washed with hot hydrochloric acid (1:40). The filtrate is saved. Filters of sediment (A and B) tungsten trioxide and silica may contain small amounts of molybdenum, which determine an extraction-photometric method, and the result added to the result of a gravimetric determination. Filters of sediment (A and B) were placed in a glass with a capacity of 250 cm
, and dissolved in 20 cm
of hot sodium hydroxide solution. Then pour 100 cm
of hot water and filtered through filter «white ribbon» in a volumetric flask with a capacity of 250 cm
. The filter is washed with hot water containing a few drops of sodium hydroxide. To the solution was added 20 cm
of ammonium citrate solution and mix. Then add sulfuric acid (1:1) to pH 7−8 (universal indicator paper) and pour 5 cm
in excess. The solution was cooled, made up to the mark with water and mix. Aliquot part of the solution is equal to 25 cm
, placed in a separatory funnel with a capacity of 150−200 cm
, flow 10 cm
of hydrochloric acid (1:1), 5 cm
of a solution of sulphate of copper, 5 cm
of a solution of ascorbic acid and then act as indicated in
p.
4.3.3. The separation of molybdenum from other elements with sodium hydroxide and determination in the form of molybdate of lead
To the filtrate, obtained according to the PP. 4.3.1 or 4.3.2, poured a solution of hydrate of sodium oxide before the deposition of small sediment, vanishing with stirring. The precipitate is dissolved by adding into the solution a few drops of sulfuric acid (1:1).
If the steel contains vanadium or chromium in the solution was added to 25 cmof a solution of sodium semitecolo.
The solution is heated to 80−90 °C and cautiously, with constant stirring, poured into a volumetric flask with a capacity of 500 cmcontaining 100 cm
, heated to the boiling point of the solution of hydrate of sodium oxide. The contents of the flask are cooled, made up to the mark with water, mixed and allowed to settle sediment within 1−2 h. the Solution was filtered through a dry filter into a glass or flask, discarding first portion of filtrate.
Aliquoting a portion of the filtrate equal to 250 cm, placed in a beaker with a capacity of 600 cm
, add 2−3 drops of solution of methyl red, hydrochloric acid (1:1) until the color of the solution in red color, then add 2 cm
of acid in excess, and 20 g of ammonium acetate.
4.3.3.1. The solution is heated to boiling, poured with constant stirring 10−20 cm(depending on the content of molybdenum in steel) acetate of lead, boiled for 10−15 minutes and to verify the completeness of deposition, add a few drops of acetate of lead. The beaker with the precipitate of lead molybdate maintained at 80 °C for 1 h.
The precipitate is filtered on two filters «white ribbon» and washed with acetic acid (1:40) prior to the removal of lead ions, and then with hot water. The filter with precipitate was placed in a porcelain, preheated to constant mass and weighed crucible, dried, incinerated at 400 °C and then calcined at 500−600 °C to constant weight. The crucible with residue was cooled in a desiccator and weighed.
4.3.4. The separation of molybdenum from other elements -benzoylation and determination in the form of molybdate of lead
The filtrate, obtained according to the PP. 4.3.1 and 4.3.2, is evaporated to a volume of 100 cm, cool and add 0.5−0.8 g of iron sulfate for the recovery of vanadium and chromium.
The solution was cooled to 5−10°C, slowly add 10 cmof solution
-benzoyloxy, and then 5 cm
in excess for every 0.01 g of molybdenum. The solution is mixed, add bromine water to a yellow color and a 5 cm
mortar
-benzoyloxy.
The solution with precipitate was cooled to 5−10 °C, stirring occasionally, add filtrowanie mass and the precipitate was filtered off on the filter «blue ribbon». If the first 50 cmof the opaque filtrate, filtration of the solution is repeated using the same filter.
The filter residue is washed with wash liquid. The precipitate from the filter washed with water in a glass, which conducted the deposition. The filter is saved. To the beaker was added 10 cmammonia and 10 cm
of hydrogen peroxide solution, pour water to a volume of 75−80 cm
and boil until complete removal of the oxygen bubbles.
The solution was filtered through the same filter and washed with hot ammonia solution. The filter is discarded. The solution is neutralized with hydrochloric acid in presence of methyl red indicator, hydrochloric acid add 2 cmin excess of, 40 cm
of a solution of ammonium acetate concentration of 500 g/DM
and further analysis performed as described in section
(Redrafted From
M. N 1).
4.4. Processing of the results
Mass fraction of molybdenum in percent is calculated by the formula
where is the mass of the precipitate of lead molybdate in the sample, g;
— the mass of the precipitate of lead molybdate in a control experiment, g;
— the weight of the portion contained in aliquote part of the solution, g;
0,2613 — the conversion factor of lead molybdate to molybdenum.
5. ATOMIC ABSORPTION METHOD FOR THE DETERMINATION OF MOLYBDENUM
5.1. The essence of the method
The method is based on dissolving the sample in a mixture of sulfuric and phosphoric acids. After evaporation of the solution until the appearance of fumes of sulphuric acid and dilution with water the solution is sprayed into the flame nitrous oxide-acetylene and measure the absorption of molybdenum at a wavelength of 313,3 nm.
5.2. Equipment and reagents
Atomic absorption spectrophotometer fiery.
Lamp with hollow cathode for the determination of molybdenum.
Acetylene according to GOST 5457−75.
The nitrous oxide.
Hydrochloric acid by the GOST 3118−77 or GOST 14261−77.
Nitric acid GOST 4461−77 or GOST 11125−84 and diluted 1:4.
Sulfuric acid GOST 4204−77 or GOST 14262−78 and diluted 1:1.
Orthophosphoric acid according to GOST 6552−80.
A mixture of acids: hydrochloric and nitric in the ratio of 3:1.
A mixture of sulphuric and phosphoric acids: in a volumetric flask with a capacity of 1 DMcontaining 500 cm
of water is added with continuous stirring 150 cm
of sulphuric acid, then 150 cm
of phosphoric acid. The solution was cooled, made up to the mark with water and mix.
Radio engineering carbonyl iron according to GOST 13610−79.
The solution of iron: 25 g of carbonyl iron is dissolved in 100 cmof hydrochloric acid and gently oxidize a small amount of nitric acid. The solution was cooled, transferred to a volumetric flask with a capacity of 500 cm
, made up to the mark with water and mix.
Ammonium chloride according to GOST 3773−72, a solution of 50 g/DM.
Molybdenum metal brand MCIT.
Standard solutions of molybdenum.
Solution a: 0.5 g of a metallic molybdenum dissolved in 5 cmof sulphuric acid (1:1) and 20 cm
of nitric acid (1:4) with moderate heating. The solution was cooled, transferred to a volumetric flask with a capacity of 500 cm
, made up to the mark with water and mix.
1 cmof the solution contains 0.001 g of molybdenum.
Solution B: 25 cmsolution And transferred to a volumetric flask with a capacity of 100 cm
, made up to the mark with water and mix.
1 cmof solution B contains 0.00025 g molybdenum is prepared on the day of application.
(Redrafted From
M. N 1).
5.3. Preparation of the device
The training device is carried out in accordance with the attached instructions. Set the spectrophotometer at a resonance line 313,3 nm.
After turning on gas supply and ignition of the burner spray water into the flame and set the instrument zero.
5.4. Analysis
Weighed 0.5 g of steel placed in a beaker with a capacity of 250 cmadd 30 cm
of a mixture of sulfuric and phosphoric acids and then heated. After the dissolution of the steel sample solution is oxidized by adding dropwise nitric acid until the termination of foaming, and is evaporated until the appearance of sulphuric acid fumes.
If the steel is not soluble in a mixture of sulfuric and phosphoric acids, a sample of steel is dissolved in 30−50 cmof a mixture of hydrochloric and nitric acids by heat. The solution is evaporated to small volume, cooled, and then add 30 cm
of a mixture of sulfuric and phosphoric acids, is evaporated until the appearance of sulphuric acid fumes and cooled.
Allowed other ways of dissolution of batches, ensuring complete decomposition of the sample and does not require changes in the further stage of the analysis.
In a glass add 30−40 cmof water, heated to dissolve salts and after cooling transferred to a volumetric flask with a capacity of 100 cm
, made up to the mark with water and mix.
The solution is filtered over a dry filter «white ribbon», discarding the first two portions of the filtrate.
Aliquote part of the solution is placed in a volumetric flask with a capacity of 100 cm, add the iron solution in the amount indicated in the table.2.
Table 2
| Mass fraction of molybdenum, % |
The content of molybdenum in the sample solution, µg/cm |
Dilution of the main solution, cm |
The dilution factor |
The volume of the solution of iron, see |
| From 0.01 to 0.50 |
From 0.5 to 25 |
100 | 1 | 0 |
| SV. Of 0.50 «to 2.5 |
«5» 25 |
20/100 | 5 | 8 |
| Is 2.5 of 5.0 |
«12,5» 25 |
10/100 | 10 | 9 |
Then add 10 cmof a solution of ammonium chloride, adjusted to the mark with water and mix.
To a solution of the reference experiment is introduced 10 cmof a solution of iron and all other solutions used during the analysis.
Allowed another dilution of solutions so that the final concentration of molybdenum was in the range corresponding to the straight-line segment calibration curve.
Is sprayed into the flame of the solution in the reference experiment, and then analyze the solutions in order of increasing concentration of molybdenum to obtain stable readings for each solution.
Prior to introduction into the flame each of the analyzed solution is sprayed water to wash the system and check the zero point. From the average of optical density of the analyzed solution is subtracted the average value of optical density in the reference experiment.
A lot of find molybdenum in the calibration schedule.
5.4.1. Construction of calibration curve
Seven of cups with a capacity of 250 cmis placed 10 cm
solution of iron and six of them successively poured 0,2; 1,0; 2,5; 5,0; 7,5 and 10,0 cm
standard solution B, which corresponds to 0,05; 0,25; 0,625; 1,25; 1,875 and 2.5 mg of molybdenum. The seventh glass is used for the reference experiment.
In each glass pour 30 cmof a mixture of sulfuric and phosphoric acids. The solution is heated, oxidized by adding dropwise nitric acid, and evaporated until the appearance of sulphuric acid fumes. After cooling, add 30−40 cm
of water, heated to dissolve the salts and transferred to a volumetric flask with a capacity of 100 cm
, add 10 cm
of a solution of ammonium chloride, made up to the mark with water and mix.
The device is tuned to the resonance line 313,3 nm. Solutions injected into the flame in order of increasing concentration of molybdenum, starting with the solution in the reference experiment. Before spraying each solution is sprayed water. From the mean values of absorbance of each test solution subtract the average value of the optical density of the solution in the reference experiment.
On the found values of optical density and corresponding masses of molybdenum in building a calibration curve
.
5.5. Processing of the results
Mass fraction of molybdenum in percent is calculated by the formula
where is the mass of molybdenum in the sample was found in the calibration schedule g;
— weight of steel contained in 100 cm
of the analyzed solution,
5.4−5.5. (Changed edition, Rev. N 1).
5.6. Allowable absolute discrepancies in the results of parallel measurements at a confidence level =0.95 does not exceed the values specified in table.3, in case of disagreement in assessing the quality of alloyed and high-alloyed steels for supply of metal in the CMEA countries — table.4.
Table 3
| Mass fraction of molybdenum, % |
The absolute allowable difference, % |
| From 0.010 to 0.02 |
0,007 |
| SV. 0,02 «0,05 |
0,01 |
| «0,05» 0,10 |
0,02 |
| «To 0.10» to 0.25 |
0,03 |
| «Of 0.25» to 0.60 |
0,04 |
| SV. Of 0.60 to 1.0 |
0,05 |
| «1,0» 2,0 |
0,07 |
| «To 2.0» 5,0 |
0,1 |
| «5,0» 10,0 |
0,2 |
Table 4
| Mass fraction of molybdenum, % |
The absolute allowable difference, % |
| From 0.01 to 0.05 |
0,005 |
| SV. 0,05 «0,10 | 0,01 |
| «To 0.10» to 0.25 |
0,02 |
| «0,25» 0,50 |
0,03 |
| «0,50» 1,00 |
0,04 |
| SV. Of 1.00 to 2.00 |
0,06 |
| «2,00» 3,00 |
0,10 |
| «To 3.00» of 5.00 |
0,12 |
| «5,00» 10,00 |
0,15 |
