GOST 21639.3-93

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  ГОСТ 21639.3-93

GOST 21639.3−93 Fluxes for electroslag remelting. Methods for determination of calcium oxide and magnesium oxide

GOST 21639.3−93

Group B09

INTERSTATE STANDARD

Fluxes for electroslag remelting

METHODS FOR DETERMINATION OF CALCIUM OXIDE AND MAGNESIUM OXIDE

Fluxes for electroslag remelting.
Methods for determination of calcium oxide and magnesium oxide

OKS 71.040.040*
AXTU 0709

________________

* In the index «National standards» 2006 ACS 25.160.20. -

Note the «CODE».

Date of introduction 1996−01−01

Preface

1 PREPARED by the Russian Federation Technical Committee TC 145 «monitoring Methods of steel products"

SUBMITTED by the Technical Secretariat of the Interstate Council for standardization, Metrology and certification

2 ADOPTED by the Interstate Council for standardization, Metrology and certification 17 February 1993.

The adoption voted:

3 Decree of the Russian Federation Committee on standardization, Metrology and certification from 14.06.95 No. 298 inter-state standard GOST 21639.3−93 introduced directly as state standard of the Russian Federation from January 1, 1996

4 REPLACE GOST 21639.3−76

1 SCOPE

This standard specifies the titrimetric and atomic absorption methods for the determination of calcium oxide in a mass proportion of from 1 to 65% and magnesium oxide in a mass proportion of from 2% to 27%.

2 NORMATIVE REFERENCES

The present standard features references to the following standards:

GOST 3118−77 hydrochloric Acid. Specifications

GOST 3760−79 Ammonia water. Specifications

GOST 3772−74 Ammonium phosphate disodium. Specifications.

GOST 3773−72 Ammonium chloride. Specifications

GOST 4140−74 Strontium chloride 6-water. Specifications

GOST 4204−77 sulfuric Acid. Specifications

GOST 4234−77 Potassium chloride. Specifications

GOST 4332−76 Potassium carbonate — sodium carbonate. Specifications

GOST 4526−73 Magnesium oxide. Specifications*

GOST 4530−76 Calcium carbonate. Specifications

GOST 5456−79 of Hydroxylamine hydrochloride. Specifications

GOST 5457−75 Acetylene, dissolved and gaseous. Specifications

GOST 5712−78 Ammonium oxalate 1-aqueous. Specifications

GOST 5839−77 Sodium oxalate. Specifications

GOST 8677−76 Calcium oxide. Specifications

GOST 8864−71 Sodium N, N-diethyldithiocarbamate 3-water. Specifications

GOST 9656−75 boric Acid. Specifications

GOST 10652−73 Salt is the disodium Ethylenediamine-N, N', N'-tetraoxane acid, 2-water (Trilon B).

GOST 11293−89 Gelatin. Specifications

GOST 20478−75 Ammonium neccersarily. Specifications

GOST 20490−75 Potassium permanganate. Specifications

GOST 21639.0−93 Fluxes for electroslag remelting. General requirements for methods of analysis

GOST 21639.3−93 Fluxes for electroslag remelting. Methods for determination of aluminium oxide**

GOST 24363−80 Potassium hydroxide. Specifications

________________
* Probably a mistake of the original. Should read GOST 4526−75;
** Probably a mistake of the original. Should read GOST 21639.2−93. — Note the CODE.

3 GENERAL REQUIREMENTS

General requirements for methods of analysis GOST 21639.0.

4 TITRIMETRIC METHOD FOR THE DETERMINATION OF CALCIUM OXIDE

4.1 the essence of the method

The method is based on titration in alkaline medium at pH 12 calcium ions by Trilon B in the presence of metallindustri of fluoresone or mixture of indicators calcein and thymolphthalein.

Method applies for determination of total content of calcium oxide in the amount of compounds of calcium oxide and calcium fluoride.

4.2 Reagents and solutions

Hydrochloric acid according to GOST 3118 and the solution with molar concentration of 1 mol/land diluted 1:1.

Potassium hydroxide according to GOST 24363, a solution with a mass concentration of 5 and 200 g/DM.

Potassium chloride according to GOST 4234.

Indicator fluoresce 0.2 g of the indicator is triturated in a mortar with 20 g of potassium chloride.

Calcium oxide according to GOST 8677.

Fluorescent indicator: 2 g calcein disodium salt was placed in a dry flask of 500 cmand dissolved in 200 cmof a solution of potassium hydroxide with a mass concentration of 5 g/DM. Add to the solution by portions under agitation to 40 cmof hydrochloric acid with molar concentration of 1 mole/DM. The solution was filtered into a flask with a capacity of 1 DM. The filter cake was washed with acidified water (per 1 DMof water 2 cmof hydrochloric acid solution with molar concentration of 1 mole/DM) to the filtrate volume of 1 DM.

Thymolphthalein solution with a mass concentration of 2 g/lsolution of calcium oxide with a mass concentration of 5 g/DM.

Indigo 5,5 — disulfonate dipotassium salt, indicator (Indigo Carmine), an aqueous solution with a mass concentration of 25 g/DM.

Ammonium neccersarily according to GOST 20478, a freshly prepared solution with a mass concentration of 100 g/DM.

The indicator methyl red, alcoholic solution with a mass concentration of 1 g/DM.

Hydroxylamine hydrochloride according to GOST 5456, solution with a mass concentration of 200 g/DM.

Ammonium chloride according to GOST 3773, a solution with a mass concentration of 200 g/DM.

Ammonia water according to GOST 3760, diluted 1:1.

Sodium N, N-diethyldithiocarbamate according to GOST 8864, solution with a mass concentration of 100 g/DM.

Ammonium oxalate according to GOST 5712, solutions with a mass concentration of 1 and 40 g/DM.

Salt is the disodium Ethylenediamine-N, N, N', N'-tetraoxane acid, 2-water (Trilon B) according to GOST 10652, solutions with molar concentration of 0.025 mol/l, prepared according to GOST 21639.2.

Universal indicator paper.

The indicator methyl orange, the solution with a mass concentration of 1 g/DM.

Calcium carbonate according to GOST 4530.

Standard solutions

Solution a: 1,785 g of calcium carbonate, previously dried at a temperature of (105±5) °C to constant weight, is placed in a beaker with a capacity of 300−400 cm, add 100 cmof water, 20 cmof hydrochloric acid (1:1) and heated until complete dissolution. The solution is boiled for 3−4 min, cooled, poured into a volumetric flask with a capacity of 1 DM, made up to the mark with water and mix.

The mass concentration of the solution And sets the gravimetric method.

Aliquote three parts of solution A at 20 cmis placed in a conical flask with a capacity of 250 cm, flow at 100 cmof hot water at 50 cmof a solution of ammonium oxalate with a mass concentration of 40 g/DM, and leave the solutions with the fallen sediment of calcium oxalate in a warm place for 10−15 minutes. Then add 2−3 drops of methyl red, and neutralize with ammonia until the color changes of the indicator and add 1 cmof ammonia in excess. The solutions and the precipitate was boiled for 1−2 min and after 15−18 h, the precipitate of calcium oxalate is filtered on a tight filter, and then washed 6−8 times with a solution of ammonium oxalate with a mass concentration of 1 g/DM. The filter with precipitate was placed in a weighed platinum crucible, incinerated and calcined in a muffle at a temperature of 1100−1150 °C to constant weight.

Simultaneously conduct control experience for contamination of reagents.

The mass concentration of the solution And (), expressed in g of calcium oxide per 1 cmof a solution, calculated by the formula

, (1)

where is the mass of the crucible with the precipitate of calcium oxide, g;

 — weight of crucible without sediment, g;

 — the mass of the crucible with the sediment in the reference experiment, g;

 — weight of crucible without the sediment in a control experiment, g;

 — the volume of solution of calcium chloride taken for analysis, cm.

Solution B: 25 cmsolution And placed in a volumetric flask with a capacity of 250 cm, made up to the mark with water and mix.

Mass concentration of Trilon B set at a standard solution A: aliquot part of standard solution And 50 cmplaced in three conical flasks with a capacity of 250 cm, add 1 cmof hydroxylamine, 3−4 drops of Indigo Carmine, a thin stream while stirring pour in a solution of potassium hydroxide with a mass concentration of 200 g/DMto change the color of the solution from blue to yellow, which corresponds to pH 12. Add 0.1 g of the indicator of fluoresone or one drop of the fluorescent indicator and titrated with a solution of Trilon B before the transfer of the green fluorescent color of the solution pink.

In parallel spend control experience in the determination of the mass fraction of calcium in the reagent and water.

Mass concentration of Trilon B (), expressed in g of calcium oxide per 1 cmof a solution, calculated by the formula

, (2)

where is the mass concentration of calcium oxide in standard solution, %;

 — the weight of the portion corresponding to aliquote part of the solution, g;

 — volume of solution Trilon B, used for titration of aliquots part of standard solution A, cm;

 — volume of solution Trilon B, used for titration of a solution of calcium oxide in solution in the reference experiment, cm.

4.3 analysis

The filtrate and washings after separation of sesquioxides oxides according to GOST 21639.2 evaporated to a volume of 100−120 cm, neutralized with ammonia to a faint smell, give 5 cmof ammonia in excess, add 5 cmnaternicola ammonium, the solution was heated for 10−12 min solution and the precipitate was placed in a volumetric flask with a capacity of 500 cm, cooled, adjusted to the mark with water, mixed well, filtered through a dry filter medium density in a dry flask.

To determine the total content of calcium oxide in the amount of calcium oxide and calcium fluoride and the amount of total calcium oxide and magnesium oxide in two conical flasks with a capacity of 250 cmtaken aliquote parts of a solution of 100 cm. To one of flasks with aliquots part pour 1 cmof a solution of hydroxylamine, 3−4 drops of solution of Indigo, and a thin stream pour with energetic stirring, a solution of potassium hydroxide with a mass concentration of 200 g/DMto change the color of the solution from blue to yellow, add fluoresce or one drop of thymolphthalein and one drop of the fluorescent indicator and slowly titrated with a solution of Trilon B (in the determination of calcium oxide up to 10% using the solution Trilon B with molar concentration of 0.0125 mol/DM, more than 10% of Trilon B with molar concentration of 0.025 mol/DM), tucked under the bottom of the flask with black paper, to change a green fluorescent color of the solution pink.

Are parallel to control the experience on the content of calcium oxide in the reactants and in

ode.

4.4 Processing of results

4.4.1 overall Mass fraction of calcium oxide in the amount of compounds of calcium oxide and calcium fluoride () in percent is calculated by the formula

, (3)

where is the mass concentration of the solution Trilon B, expressed in g of calcium oxide per 1 cmof solution;

 — volume of solution Trilon B, used for titration of aliquots part of the sample, cm;

 — volume of solution Trilon B, used for titration of calcium oxide in solution in the reference experiment, cm;

 — the weight of the portion corresponding to aliquote part of the solution,

Mass fraction of calcium oxide () in percent is calculated by the formula

, (4)

where  — mass fraction of total calcium oxide in the amount of compounds of calcium oxide and calcium fluoride, %;

 — mass fraction of calcium fluoride, %;

 — the ratio of calcium fluoride to calcium oxide.

4.4.2 Standards of accuracy and standards for monitoring the accuracy of determining the mass fraction of total calcium oxide in the amount of compounds of calcium oxide and calcium fluoride are shown in table 1.


Table 1 — Standards of accuracy control

Note. When determining the mass fraction of calcium oxide in the results of the analysis introduced additional error due to the error of determination of calcium fluoride (4), which must be taken into account in the valuation accuracy of the analysis and is calculated according to the formula

, (5)

where is the corresponding norm or standard of control of the accuracy of determining the mass fraction of calcium oxide;

 — Norma (normative) determination of the total calcium oxide in the amount of compounds of calcium oxide and calcium fluoride, are taken from table 1;

 — norm (the standard) determine the mass fraction of calcium fluoride (table 1 GOST 21639.7);

 — the ratio of calcium fluoride to calcium oxide.

5 PERMANGANATE TITRIMETRIC METHOD FOR THE DETERMINATION OF CALCIUM OXIDE

5.1 the essence of the method

The method is based on titration potassium permanganate oxalic acid, released during the dissolution of the precipitate of calcium oxalate in dilute sulphuric acid in quantity equivalent to the amount of calcium in solution. Calcium oxalate is precipitated in the filtrate after prior separation of interfering components hexamine.

5.2 Reagents and solutions

Sodium oxalate according to GOST 5839, solution with a mass concentration of 40 g/DM.

Sulfuric acid according to GOST 4204, diluted 1:1, 1:10.

The other reagents and solutions — at 4.2 with the addition.

Potassium permanganate according to GOST 20490, titrated solutions with molar concentration of equivalent of 0.05, 0.1 and 0.2 mol/DM:

1,6; 3,2 and 6,4 g of potassium permanganate dissolved in water, transferred to a volumetric flask with a capacity of 1 DM, made up to the mark with water and mix. The solution is stored in container made of dark glass. The mass concentration of potassium permanganate solution set oxalate sodium. For this, 0.1−0.2 g of sodium oxalate, previously dried at a temperature of 110−120 °C, was placed in a flask with a capacity of 500 cm, add 200 cmof sulphuric acid (1:10), and the solution heated in a water bath to 75−80 °C and then titrated with solution of potassium permanganate until a stable pink color.

Mass concentration () of the solution of potassium permanganate, expressed in g of calcium oxide per 1 cmof a solution, calculated by the formula

, (6)

where  — weight of sodium oxalate, g;

 — the conversion factor of sodium oxalate to the oxide of calcium;

 — the volume of permanganate solution of sodium cm.

Allowed to set, the mass concentration of a solution of potassium permanganate in a solution of calcium oxide.

5.3 analysis

In two conical flasks with a capacity of 250 cm100 cm selectaliquote parts of a solution prepared according to 4.3, and neutralize according to methyl orange with hydrochloric acid until the color changes of the indicator. Then diluted with water to a volume of 250 cm, the solution is heated to a temperature of 90−95 °C and poured 50 cmhot solution of ammonium oxalate with a mass concentration of 40 g/DM. To the solution under stirring add ammonia until the color indicator and 1 cmin excess. Solution and the precipitate was boiled for 10 min and leave for 12 h

The precipitate of calcium oxalate is filtered off on a tight filter and washed 10−12 times with water. Then check on the completeness of the laundering of oxalic acid ions in the washing waters. To do this in a test tube take about 2 cmof the filtrate, add 2−3 drops of sulfuric acid (1:1), is heated to a temperature of 75−80 °C, add one drop of permanganate solution potassium with molar concentration of the equivalent 0,1 mol/DM. Preserving the color within 1−2 minutes indicates the fullness of the laundering. The filtrate after separation of the calcium remain to determine the content of magnesium oxide. Funnel washed with precipitate was placed on glass, which conducted the deposition and broke through the filter, wash the precipitate in the beaker with a little water. The filter is washed with hot sulfuric acid (1:10), then 5−6 times with hot water. Filter funnel save. The solution is heated to a temperature of 80−90 °C and titrated with a solution of potassium permanganate until a stable slightly pink color. Then lowered into the beaker with the titrated solution saved the filter, stirred vigorously and, if the solution becomes colorless again dotirovat solution of potassium permanganate.

For titration when the mass fraction of calcium oxide up to 7% apply the permanganate solution potassium with molar concentration of equivalent of 0.05 mol/DM; over 7 to 15% — 0.1 mol/DM; over 15% — 0.2 mol/DM.

Through all stages of the analysis, conduct test

experience.

5.4 processing of the results

5.4.1 total Mass fraction of calcium oxide () is calculated by the formula

, (7)

where mass concentration of a solution of potassium permanganate, expressed in grams of calcium oxide per 1 cmof solution;

 — the volume of potassium permanganate solution consumed for titration, cm;

 — the volume of potassium permanganate solution consumed for titration of the control experience, cm;

 — the weight of the portion of the sample,

Mass fraction of calcium oxide () in percent is calculated by the formula

, (8)

where  — mass fraction of total calcium oxide in the amount of compounds of calcium oxide and calcium fluoride, %;

 — mass fraction of calcium fluoride, %;

 — the ratio of calcium fluoride to calcium oxide.

5.4.2 Norms of accuracy and norms control the accuracy of determining the mass fraction of calcium oxide are given in table 1.

6 TITRIMETRIC METHOD FOR THE DETERMINATION OF MAGNESIUM OXIDE

6.1 the essence of the method

The method is based on the formation in solution with calcium ions and magnesium complex compounds with metalinjection chrome dark blue, painted in a lilac color, which with the introduction of Trilon B hydrolyzes with the formation of more solid compounds of calcium and magnesium. Released free the indicator changes its color in an equivalent point from purple to blue.

Mass fraction of magnesium oxide in the sample calculated by subtracting the volume of solution Trilon B, used for titration of total calcium oxide and total of calcium oxide and magnesium oxide.

6.2 Reagents and solutions

Ammonium disodium phosphate according to GOST 3772, a solution with a mass concentration of 100 g/DM.

Ammonia water according to GOST 3760 and diluted 1:20.

Ammonium chloride according to GOST 3773.

Ammonia buffer: 57.5 g of ammonium chloride dissolved in 200 cmof water, add 570 cmof ammonia, dilute with water to 1 DMand stirred.

Hydrochloric acid according to GOST 3118 and diluted 1:1.

The indicator methyl orange, aqueous solution with a mass concentration of 1 g/DM.

Potassium chloride according to GOST 4234.

The acidic indicator chrome dark blue; 0.1 g of the indicator is triturated with 10 g of potassium chloride.

Salt is the disodium Ethylenediamine-N, N, N', N'-tetraoxane acid, 2-water (Trilon B) according to GOST 10652, solution with molar concentration of 0.0125 or 0.025 mol/l, prepared according to GOST 21639.2.

The magnesium metal.

Magnesium oxide according to GOST 4526.

Standard solutions.

Solution a: 0,6031 g of magnesium or of 1.02 g of magnesium oxide, pre-calcined at a temperature of 600−900 °C, dissolved by heating at 40 cmof hydrochloric acid. The solution was then cooled, placed in a volumetric flask with a capacity of 1 DM, made up to the mark with water and mix.

The mass concentration of the solution And sets the gravimetric method.

Three aliquote part of the solution And 25 cmare placed in the beakers with a capacity of 300−400 cm, add 10 cmof hydrochloric acid and water to a volume of 150−200 cm. The solutions are poured at the 20−25 cmof a solution of phosphate of ammonia, 2−3 drops of methyl orange indicator and with vigorous stirring neutralized with ammonia, priliva it in excess of 10 cmfor every 100 cmof solution. Then the solutions were vigorously stirred with a glass rod for 1 min and left for 12 h. the Precipitate was filtered on two thick filter with a small amount filtrowanie mass, washed the Cup 2−3 times and the filter 3−4 times with ammonia (1:20). To remove excess phosphate ion filter with the precipitate is placed in a weighed platinum crucible, dried, carefully incinerated at a temperature of 450−500 °C and calcined at a temperature of 1000−1100 °C for 25−30 min, cool in desiccator, weigh. If the precipitate retains gray color, it is moistened with a few drops of 10% strength ammonium nitrate solution, carefully dried and again calcined at a temperature of 1000−1100 °C, cooled and weighed.

Simultaneously conduct control experience for contamination of reagents.

The mass concentration of a solution of magnesium chloride (), expressed in g of magnesium oxide per 1 cmof a solution, calculated by the formula

, (9)

where is the mass of the crucible with the sediment of magnesium pyrophosphate, g;

 — weight of crucible without sediment, g;

 — the mass of the crucible with the sediment in the reference experiment, g;

 — weight of crucible without the sediment in a control experiment, g;

 — the ratio of magnesium pyrophosphate on magnesium oxide;

 — the volume of a solution of magnesium chloride taken for analysis, cm.

Solution B: 10 cmsolution And placed in a volumetric flask with a capacity of 250 cm, made up to the mark with water and mix.

The mass concentration of the solution Trilon B for the magnesium set: 25 cmstandard solution And placed in a conical flask with a capacity of 250 cm, add 100 cmof water, 10 cmammonia buffer, 0.1 g of the acidic indicator chrome dark blue, mixed well and titrated with Trilon B before the solution colour from purple in blue.

The mass concentration of the solution Trilon B (), expressed in g of magnesium oxide per 1 cmof a solution, calculated by the formula

, (10)

where is the mass of magnesium in 1 cmstandard solution, g;

 — the volume of a standard solution of magnesium oxide, cm;

 — the ratio of magnesium to magnesium oxide;

 — volume of solution Trilon B, used for titration of standard solution of magnesium oxide, cm;

 — volume of solution Trilon B, used for titration of the solution of the control ops

one cm.

6.3 analysis

To determine the amount of calcium oxide and magnesium oxide to the second aliquote part of the solution obtained in 4.3, poured 10 cmof ammonium buffer, add 0.1 g of the indicator chrome dark blue. The solution was titrated with Trilon B before a sharp transition in color of the solution from purple to blue.

In parallel spend control experience on the content of the sum of calcium oxide and magnesium oxide in the reagent and water.

6.4 Processing of results

6.4.1 Mass fraction of magnesium oxide () in percent is calculated by the formula

, (11)

where  — volume of solution Trilon B, used for titration of total calcium oxide and magnesium oxide, cm;

 — volume of solution Trilon B, used for titration of total calcium oxide and magnesium oxide in the solution in the reference experiment, cm;

 — volume of solution Trilon B, used for titration of total calcium oxide, cm;

 — volume of solution Trilon B, used for titration of total calcium oxide in solution in the reference experiment, cm;

 — mass concentration of the solution Trilon B, expressed in grams of magnesium oxide per 1 cmof solution;

 — weight naves

and,

6.4.2 the Norms of accuracy and norms control the accuracy of determining the mass fraction of magnesium oxide are shown in table 2.


Table 2 — Standards for monitoring the accuracy of determining the mass fraction of magnesium oxide

7 RAPID TITRIMETRIC METHOD FOR THE DETERMINATION OF CALCIUM OXIDE AND MAGNESIUM OXIDE

7.1 the essence of the method

The method is based on titration of calcium ions by Trilon B (pH 12) in the presence of metallindustri of fluoresone or of the fluorescent indicator and the sum of calcium and magnesium (pH 9) in the presence of the indicator chrome dark blue. The magnesium content is set at the difference between the first and second titration.

7.2 Reagents and solutions — for 4.2 and 6.2.

7.3 analysis

In a volumetric flask with a capacity of 250 cmplaced 100 cm inbasic solution, prepared according to GOST 21639.2, add 20 cmof a solution of ammonium chloride with a mass concentration of 200 g/DM, two drops of methyl red and neutralize with ammonia (1:1), heated 5 min for coagulation Sesqui-oxides. Cool, add 5 cmof a solution of sodium diethyldithiocarbamate, close the flask with a stopper and vigorously stirred for 2−3 min, adjusted to the mark with water, mixed, filtered through a dense filter into a dry flask. Select two aliquote part of the solution to 100 cmin a conical flask with a capacity of 250 cm. In one of the flasks to determine the total calcium oxide in the other — the total of calcium oxide and magnesium oxide. In a flask, which defines the oxide of calcium, add 1 cmof a solution of hydrochloride of hydroxylamine, four drops of the indicator Indigo-Carmine, neutralized with a solution of potassium hydroxide with a mass concentration of 200 g/DMbefore the solution colour from blue to yellow, add 0.1 g of fluoresone or mixture of indicators and titrated with Trilon B on a black background to the disappearance of green fluorescence.

In parallel spend control experience.

In a flask, which determine the amount of total calcium oxide and magnesium oxide, is poured 10 cmof ammonium buffer, add 0.1 g of the indicator chrome dark blue. The solution was titrated with Trilon B before a sharp transition in color of the solution from purple to blue.

In parallel spend control experience on the content of total calcium oxide and magnesium oxide in the reactants and in

ode.

7.4 processing of the results

Processing of the results by 4.4 to determine the total mass fraction of calcium oxide in the amount of compounds of calcium oxide and calcium fluoride, and 6.4 to determine the mass fraction of magnesium oxide.

8 ATOMIC ABSORPTION METHOD

8.1 the essence of the method

The method is based on measuring the degree of absorption of resonance radiation by free atoms of calcium and magnesium, formed as a result of spraying the test solution into the flame of air-acetylene or nitrous oxide-acetylene.

Mass fraction of calcium oxide is determined in the amount of compounds of calcium oxide and calcium fluoride in the range from 1 to 25%.

8.2 Apparatus, reagents and solutions

Spectrophotometer atomic absorption of any kind with the radiation source for calcium and magnesium.

Muffle furnace with heating temperature up to 1000 °C.

Acetylene is dissolved according to GOST 5457.

Nitrous oxide gas.

The compressor with the receiver, providing compressed air, or compressed air, or compressed air from the air duct with the inlet pressure in the spectrophotometer for at least 2 ATM.

Hydrochloric acid according to GOST 3118 and diluted 1:1 and 2:100.

Boric acid according to GOST 9656.

Potassium carbonate — sodium carbonate according to GOST 4332.

Mix for fusion: two parts potassium carbonate — sodium carbonate is mixed with one part boric acid.

The lanthanum nitrate solution with a mass concentration of 50 g/DM.

Strontium chloride 6-water according to GOST 4140, a solution with a mass concentration of 30 g/DM.

Gelatin food according to GOST 11293, solution with mass concentration 10 g/DM.

Calcium carbonate according to GOST 4530.

Standard solutions prepared in 4.2.

The magnesium metal.

Magnesium oxide according to GOST 4526.

The standard solutions prepared according to 6.2.

8.3 analysis

8.3.1 the flux Linkage with a mass of 0.1 g was placed in a platinum crucible, mixed with 2 g of a mixture for fusion and fused in a muffle furnace at a temperature of 950−1000 °C for 15 min.

The cooled crucible is placed in a beaker with a capacity of 250 cm, 100 cm pourwarm water, 10 cmof hydrochloric acid and heated to dissolve the salts. The crucible is removed from the beaker and washed with water. The contents of the Cup on the plate is evaporated to wet salts, poured 40 cmof hydrochloric acid and heated to dissolve the salts, then pour 60 cmof hot water, 10 cmgelatin solution, mix, allow to stand in a warm place for 5−7 min and filtered silicic acid through the filter medium density in a volumetric flask with a capacity of 250 cm.

Precipitate was washed 3−4 times with hot hydrochloric acid (2:100), then 5−6 times with hot water, the contents of the flask are cooled, made up to the mark with water and mix.

Depending on the total mass fraction of calcium oxide (the total amount of compounds of calcium oxide and calcium fluoride) and magnesium oxide taken aliquot part of the solution in accordance with table 3.


Table 3 — Volume aliquote part of the solution, depending on the mass fraction of calcium oxide and magnesium oxide

Then aliquot part of the solution placed in a conical flask with a capacity of 100 cm, was evaporated to wet salts, pour 4 cmof hydrochloric acid, 20 cmof hot water and heated to dissolve the salts. The cooled solution is placed in a volumetric flask with a capacity of 100 cm, pour 5 cmof a solution of nitrate of lanthanum or 5 cmof strontium chloride, made up to the mark with water and mix.

Through the analysis of spend control experience.

Spray the solution in the reference experiment and the sample solution into the flame of air-acetylene or nitrous nitrogen-acetylene is in the order of increasing absorption to obtain stable readings for each solution.

Before spraying each solution is sprayed water to wash the system and check the zero point. Measure the atomic absorption of calcium at a wavelength 422,7 nm and magnesium at a wavelength of RUB 285.2 nm.

After subtracting the atomic absorption reference experiment from the value of atomic absorption of a solution of the sample find the mass concentration of calcium oxide or magnesium oxide in a solution of a test portion for calibration schedule.

8.3.2 Construction of calibration curve

For construction of calibration curve eight platinum crucibles placed 2 g of a mixture of alloying and conduct analysis 8.3.1.

In seven conical flasks with a capacity of 100 cmpour 1,0; 3,0; 5,0; 7,0; 9,0; 11,0; 13,0 cmstandard solution of calcium oxide, which corresponds to 0,0001; 0,0003; 0,0005; 0,0007; 0,0009; 0,0011; 0,0013 g of calcium oxide and 0,5; 1,0; 1,5; 2,0; 2,5; 3,0; 5,0 cmstandard solution B magnesium oxide, which corresponds to 0,00002; 0,00004; 0,00006; 0,00008; 0,0001; 0,00012; 0,0002 g of magnesium oxide, pour 5 cmof a solution of nitrate of lanthanum or 5 cmof a solution of chloride of strontium, 4 cmof hydrochloric acid, made up to the mark with water and mix. The eighth bulb, containing the standard solutions used for the control experience.

Measurement of atomic absorption of the resulting solutions is carried out as specified in 8.3.1.

8.4 processing of the results

8.4.1 total Mass fraction of calcium oxide (in the amount of compounds of calcium oxide and calcium fluoride) and mass fraction of magnesium oxide () in percent is calculated by the formula

, (12)

where is the mass concentration of calcium oxide (magnesium oxide) in the solution of the sample, was found in the calibration schedule, g/cm;

 — the volume of solution used for measurement of absorption, cm;

 — the weight of the portion of the sample,

Mass fraction of calcium oxide () in percent is calculated by the formula

, (13)

where  — mass fraction of total calcium oxide (in the amount of compounds of calcium oxide and calcium fluoride), %;

 — mass fraction of calcium fluoride, %;

 — the ratio of calcium fluoride to calcium oxide.

8.4.2. Norms of accuracy and norms of control determine the mass fraction of calcium oxide and magnesium oxide are given in tables 1 and 2.