GOST 12359-99

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  ГОСТ 12359-99

GOST 12359−99 (ISO 4945−77) Steels carbon, alloyed and high alloy. Methods for determination of nitrogen

GOST 12359−99
(ISO 4945−77)

Group B39

INTERSTATE STANDARD

STEELS CARBON, ALLOYED AND HIGH-ALLOYED

Methods for determination of nitrogen

Carbon, alloyed and high-alloyed steels.
Methods for determination of nitrogen

ISS 77.040.40*
AXTU 0709
_______________
* International classification for standards
77.040.40 code is not given. — Note the CODE.

Date of introduction 2000−07−01

Preface

1 DEVELOPED by the Interstate technical Committee for standardization MTK 145 «monitoring Methods of steel products"

INTRODUCED by Gosstandart of Russia

2 ADOPTED by the Interstate Council for standardization, Metrology and certification (Protocol No. 15−99 dated may 28, 1999)

The adoption voted:

3 Appendix a contains the full authentic text of international standard ISO 4945−77 «Steel. The determination of nitrogen. A spectrophotometric method"

4 Resolution of the State Committee of the Russian Federation for standardization and Metrology dated October 21, 1999 N 360, interstate standard GOST 12359−99 (ISO 4945−77) introduced directly as a state standard of the Russian Federation from July 1, 2000.

5 REPLACE GOST 12359−81

1 Scope

This standard establishes photometric (spectrophotometric) method for determination of nitrogen with the help of nessler’s reagent (at a mass fraction of nitrogen from 0.002 to 0.01%) and titrimetric method for the determination of nitrogen (at a mass fraction of nitrogen from 0.005 to 0.50%) in carbon, alloy and high-alloy steels.

Allowed spectrometric method for the determination of nitrogen with sodium nitroprusside according to the international standard ISO 4945 (Appendix A).

2 Normative references

The present standard features references to the following standards:

GOST 83−79 Sodium carbonate. Specifications

GOST 3640−94 Zinc. Specifications

GOST 3769−78 Ammonium sulfate. Specifications

GOST 4145−74 Potassium sulfate. Specifications

GOST 4165−78 Copper (II) sulfate 5-water. Specifications

GOST 4328−77 Sodium hydroxide. Specifications

GOST 4463−76 Sodium fluoride. Specifications

GOST 8677−76 Calcium oxide. Specifications

GOST 9285−78 Potassium hydroxide technical. Specifications

GOST 14261−77 hydrochloric Acid of high purity. Specifications

GOST 14262−78 sulphuric Acid of high purity. Specifications

GOST 18300−87 ethyl rectified technical. Specifications

GOST 20490−75 Potassium permanganate. Specifications

GOST 28473−90 Iron, steel, ferroalloys, chromium and manganese metal. General requirements for methods of analysis

3 General requirements

General requirements for methods of analysis GOST 28473.

4 Photometric (spectrophotometric) method for the determination of nitrogen

4.1 the essence of the method

The method is based on dissolution of steels in non-oxidising acids, decomposition of the formed ammonium salts with sodium hydroxide, distilling the ammonia with steam or air aspiration from the alkaline test solution, and determining it in the condensate with the help of nessler’s reagent.

4.2 Equipment, reagents and solutions

Installation for the distillation of ammonia with steam (figure 1) consists of the distillation flask 1, hoppers 2 and 3, the refrigerator 4, flask-trap 5, the steam generator 7, the heater of the steam generator 8, laboratory autotransformer 9, the water bottle 6 and the bulb receiver 10.

Figure 1 — Diagram of apparatus for distillation of ammonia from steam

Figure 1 — Diagram of apparatus for distillation of ammonia from steam

Installation for the distillation of ammonia with air aspiration (figures 2 and 3) consist of air-cleaning systems 1 and 2 (1 — leaching vessel filled with sulphuric acid of density 1.84 g/cm, 2 — wash vessel filled with water), electric, 7, distillation flask of heat-resistant glass with a capacity of 500 cm, is equipped with a funnel with stopcock, 6, 3 refrigerator, vessel for trapping of nitrogen (as ammonia) 5, microburette 4 (class 1).

Figure 2 — Scheme of installation for the distillation of ammonia with air aspiration

Figure 2 — Scheme of installation for the distillation of ammonia with air aspiration

Figure 3 — diagram of an apparatus for distillation of ammonia with air aspiration

Figure 3 — diagram of an apparatus for distillation of ammonia with air aspiration

Flask to dissolve the sample (figure 4).

Figure 4 — the Flask to dissolve the sample

Figure 4 — the Flask to dissolve the sample

Distilled water free from ammonium ions, for the preparation of aqueous solutions and analysis. Water test for the presence of ammonium ions by the help of nessler’s reagent: to 200 cmof water pour 2.5 cmof the help of nessler’s reagent, stirred and allowed to stand for 15 minutes If the water is not stained to a yellowish color (the optical density of the solution measured by the spectrophotometer in a cuvette with a thickness of working layer 1 cm at a wavelength of 400 nm, not more than 0.05), it can be used to determine nitrogen. If there is yellow staining, water purified on ion-exchange resins — strong acid cation exchange resin and strong-base anion exchange resin with the resin layer height 0.2 m, diameter is 0.025 m, passing through the column at a rate of 7 to 10 cm/min.

For cleaning water using potassium permanganate 500 cmof water placed in a flask with ground joint, add potassium permanganate to a faint staining and boil for 30 min, Then added 100 g of calcium oxide and boiled for 2 h. Connect the flask with a refrigerator and collect the distillate in a bottle with a ground stopper.

Water can be purified also by any other method giving the optical density of colored solution to a value of 0.05.

Copper sulfate according to GOST 4165.

Zinc metal according to GOST 3640.

Hydrochloric acid according to GOST 14261, diluted 1:1.

Sulfuric acid according to GOST 14262, diluted 1:4.

Sulfuric acid with molar concentration of equivalent of 0.01 mol/DM, prepare fiksanala.

Potassium sulfate according to GOST 4145, calcined at a temperature of 900 °C.

Sodium hydroxide according to GOST 4328, solution mass concentration of 40 g/100 cmand 200 g of sodium hydroxide dissolved in 600 cmof water, and is evaporated by boiling to 500 cmwith the addition of a few granules of zinc.

Potassium hydroxide according to GOST 9285, solutions of the mass concentration of 60 g/100 cmand 15 g/100 cm.

Sodium fluoride according to GOST 4463.

Potassium permanganate according to GOST 20490.

Calcium oxide according to GOST 8677.

Ammonium sulfate according to GOST 3769, standard solution.

Ammonium sulfate dried at (100±5) °C. a Suspension of ammonium sulfate 4,7170 g placed in a beaker of 200−400 cm, dissolved in water, transferred to a flask with a capacity of 1·10cm, made up to the mark with water and mix. 10 cmsolution is placed in another volumetric flask with a capacity of 1·10 cm, made up to the mark with water and mix.

1 cmof the resulting solution of ammonium sulfate contains 0,0000

1 g of nitrogen.

4.3 Preparation for analysis

4.3.1 Installing with steam

Assemble the installation (figure 1) and washed it before transfer of the sample solution into the distillation flask through the funnel 2 poured in a distillation flask 80 cmof sodium hydroxide solution through the funnel 3−100 cmof water and let steam for 10−15 min. Then remove the solution from the flask receiver and from the distillation flask, Prilepa in the steam generator 150−170 cmof water. When this alkaline solution is transferred from the distillation flask into the flask trap and remove.

4.3.2 Installation with air aspiration

Assemble the installation (figures 2 and 3) and check the tightness of the entire system using aspirator prosushivaniem air evenly at a speed of 3−4 bubbles per second.

To clean the system in a distillation flask poured 80 cmof sodium hydroxide solution, 100 cmof water and boil the solution for 5−10 min.

After cleaning the entire system, turn off the hot plate, water jet pump, remove the solution from the distillation flask and from the vessel for trapping nitrogen.

4.4 analysis

4.4.1 Determination of nitrogen on install with steam

4.4.1.1 Determination of nitrogen in steels with a mass fraction of silicon up to 0.5%

A sample weighing 2 g was placed in a flask (figure 4). For dissolved pour 50 cmof sulfuric acid solution (1:4) and close to its ground stopper with a water seal in the reservoir which pre-pour 2−3 cmof sulfuric acid solution (1:4).

The sample is dissolved at temperature not higher than (85±5) °C until the complete cessation of hydrogen evolution. The flask with the solution was cooled, the solution from the reservoir to the hydraulic valve attached to the main solution and wash the paddle 2−3 times with water. The solution was evaporated until the appearance of sulphuric acid fumes and cooled. To the solution was added 5 g of potassium sulfate, 1 g copper sulphate, poured 20 cmof sulphuric acid and heat the contents of the flask until the appearance of dense fumes of sulfuric acid (solution temperature is at least 340 °C).

In the absence of nitrides in the steel of the chromium is allowed for the dissolution of the sample in sulfuric acid (1:4) without the addition of concentrated sulfuric acid, potassium sulfate, copper sulphate and heating to the appearance of sulphuric acid fumes.

For insoluble steels allowed the use of other acids, ensure the completeness of dissolution of the sample.

4.4.1.2 Determination of nitrogen in steels with a mass fraction of silicon of more than 0.5%

The sample is dissolved with moderate heating in 50 cmof a solution of hydrochloric acid (1:1) to complete the termination of allocation of bubbles of hydrogen. After dissolution, the sample solution (2−3 cmof hydrochloric acid 1:1) from the reservoir to the hydraulic valve attached to the main solution and wash the paddle 2−3 times with water. To the solution was added with stirring in small portions of 1−1,5 g of sodium fluoride, after which the flask was closed again ground stopper with a water seal, and heating was continued. Fusion with acid potassium and copper is carried out according to the above method.

Allowed for dissolution of the sample instead of sodium fluoride the use of hydrofluoric acid.

In a volumetric flask as a receiver (figure 1) with a capacity of 250 cmgo 30 cmof sulfuric acid solution with molar concentration of equivalent of 0.01 mol/DM, in a distillation flask through the funnel 2 pour 80 cmof sodium hydroxide (allowed the use of potassium hydroxide solution), through a funnel 3 to the sample solution, washing the flask to decompose the sample and the funnel with small portions of water, not allowing it to drain through. Increase the heating of the steam generator and conducted to distillation until the volume of distillate reaches 150 cm.

In a volumetric flask with a condenser under stirring pour 4 cmof the help of nessler’s reagent. The contents of the flask diluted to the mark with water and mix

T.

4.4.2 Determination of nitrogen on installation with air aspiration

Dissolution of the sample is carried out as specified in 4.4.1.

The vessel for trapping nitrogen (figures 2 and 3) poured 30 cmof sulfuric acid solution with molar concentration of equivalent of 0.01 mol/DM, in a distillation flask using a funnel pour the 80 cmof sodium hydroxide solution (allowed the use of potassium hydroxide solution), through a funnel with a tap — sample solution, washing the flask to decompose the sample and the walls of the funnel in small portions of water, not allowing it to drain through. Close the valve of the funnel, include water-jet pump and the hotplate and heat the solution for 40 min. the Distillate is drained through the lower edge of the vessel to trap nitrogen in a volumetric flask with a capacity of 250 cm, and cooled slowly while stirring, pour 4 cmof the help of nessler’s reagent. The contents of the flask diluted to the mark with water and mix.

After 20 minutes, measure the optical density of the solution in the wavelength range of 395−405 nm, applying a solution of comparison water.

Under the same conditions conduct control experience in the determination of the mass fraction of nitrogen in the reagents.

Determination of nitrogen is carried out in the premises in the absence of ammonia, ammonium salts and nitric acid.

4.4.3 Construction of calibration curve

Five flasks are placed 4,0; 8,0; 12,0; 16,0; 20,0 cmstandard solution of ammonium sulfate, which corresponds to 0,002; 0,004; 0,006; 0,008; 0,010% nitrogen at a weight of 2 g and is carried out through all stages of analysis, as indicated in 4.3.1 and 4.3.2. On the found values of optical density (subject to amendments the reference experiment) and their corresponding values for nitrogen concentrations to build calibration curve.

4.5 Processing of results

4.5.1 Mass fraction of nitrogen, as amended by the control of the experience is determined by the calibration schedule.

4.5.2 Standards of accuracy and standards for monitoring the accuracy of determining the mass fraction of nitrogen is given in table 1.

Table 1

5 Titrimetric method determination of nitrogen

5.1 the essence of the method

The method is based on dissolution of steels in non-oxidising acids and decomposition of the formed ammonium salts with sodium hydroxide.

The absorption of released ammonia when conducting analysis on the installation of air aspiration is carried out with sulfuric acid solution with molar concentration of equivalent of 0.01 mol/DM, determination of ammonia by the back titration of the excess sulphuric acid with sodium hydroxide solution with molar concentration of equivalent of 0.01 mol/DM.

The absorption of ammonia when the air suction is carried out also by the indicator solution Tashiro and titration of acid on it.

5.2 the Instrument, reagents and solutions

Installation for the distillation of ammonia with steam (figure 1).

Installation for the distillation of ammonia with air aspiration (figures 2 and 3).

Flask to dissolve the sample (figure 4).

Indicator Tashiro: 0.03 g methyl red and 0.01 g of methylene blue dissolved in 100 cmof ethanol. In an alkaline environment, the indicator is green, sour — purple-red.

Sulfuric acid according to GOST 14262, diluted 1:4.

Sulfuric acid with molar concentration of equivalent of 0.01 mol/DM, prepare fiksanala.

To install the conversion factor of the prepared sulfuric acid solution with molar concentration of equivalent of 0.01 mol/ldissolve 0.02 g of sodium carbonate in 30−40 cmof distilled water (plain water). To the solution add 1−2 drops methyl orange and titrate until the yellow color transition of the solution into orange. To remove the formed carbonic acid solution boil for 2 minutes, cool and titrate to the transition of yellow colouring in orange.

The ratio of the sulfuric acid solution with molar concentration of equivalent of 0.01 mol/DMis calculated by the formula

(1)

where is the mass of sample, g;

 — the volume of sulfuric acid solution with molar concentration of equivalent of 0.01 mol/DMconsumed for titration, cm;

0,00053 — amount of sodium carbonate corresponding to 1 cmof a hydrochloric acid solution with molar concentration of equivalent of 0.01 mol/DM.

Sodium carbonate according to GOST 83, dried to constant mass at 270−300 °C.

Sodium hydroxide according to GOST 4328, solution with molar concentration of equivalent of 0.01 mol/DM.

The factor of normality is determined by titration of sodium hydroxide solution with molar concentration of equivalent of 0.01 mol/DMsulfuric acid solution of the same concentration.

Distilled water free from ammonium ions, for the preparation of aqueous solutions and analysis. Water is purified and tested for the presence of ammonium ions by the help of nessler’s reagent, as described in 4.2.

Hydrochloric acid according to GOST 14261, diluted 1:1.

Sodium fluoride according to GOST 4463.

Sodium hydroxide according to GOST 4328, solution mass concentration of 40 g/100 cm.

200 g of sodium hydroxide dissolved in 600 cmof water, and is evaporated by boiling to 500 cmwith the addition of a few granules of zinc.

Methyl red.

Methyl orange.

Methylene blue.

Rectified ethyl alcohol according to GOST 18300.

Potassium sulfate according to GOST 4145, calcined at 900 °C.

Potassium hydroxide according to GOST 9285, solution mass concentration 60 g/100 cm.

Copper sulfate according to GOST 4165.

Zinc metal according to GOST

3640.

5.3 Preparation for assay

Assemble the installation (figure 1) and washed it before transfer of the sample solution into the distillation flask through the funnel 2 poured in a distillation flask 80 cmof sodium hydroxide solution through the funnel 3 to 100 cmof water and let steam for 10−15 min.

Then remove the solution from the flask receiver and from the distillation flask, Prilepa in the steam generator 150−170 cmof water. When this alkaline solution is transferred from the distillation flask into the flask trap and remove.

5.3.1 Installation with air aspiration

Assemble the installation (figures 2 and 3), check the tightness of the entire system using aspirator prosushivaniem air evenly at a speed of 3−4 bubbles per second.

Before transferring the test solution into the distillation flask washed installation: through the funnel into the distillation flask poured 80 cmof sodium hydroxide solution, 100 cmof water and boil the solution for 5−10 min.

After cleaning the whole system includes electric hot plate, water jet pump, remove the solution from the distillation flask and from the vessel for trapping nitrogen.

5.4 analysis

5.4.1 Determination of nitrogen on install with steam

Weighed samples of 2 g at a mass fraction of nitrogen from 0.005 to 0.05% or 0.5 g — at a mass fraction of nitrogen in excess of 0.05% was placed into the flask for dissolution. When determining the content of nitrogen in the steels with a mass fraction of silicon up to 0.5% of the weighed sample is placed in a flask, poured 50 cmof sulfuric acid solution (1:4) and close to its ground stopper with a water seal in the reservoir which pre-pour 2−3 cmof sulfuric acid solution (1:4).

The suspension dissolved at a temperature of (85±5) °C until the complete termination of allocation of bubbles of hydrogen. The flask with the solution was cooled, the solution from the reservoir to the hydraulic valve attached to the main solution and wash the paddle 2−3 times with water. The solution in the flask was evaporated until the appearance of sulphuric acid fumes and cooled. To the solution was added 5 g of potassium sulfate, 1 g copper sulphate, poured 20 cmof sulphuric acid and heat the contents of the flask until the appearance of fumes of sulfuric acid (solution temperature is at least 340 °C).

In the absence of nitrides in the steel of the chromium is allowed for the dissolution of the sample in sulfuric acid (1:4) without the addition of concentrated sulfuric acid, potassium sulfate, copper sulphate and heating to fumes of sulphuric acid.

For insoluble steels allowed the use of other acids, ensure the completeness of dissolution of the sample.

In the determination of nitrogen in steels containing more than 0.5% silicon, the sample is dissolved with moderate heating in 50 cmof a solution of hydrochloric acid (1:1) to complete the termination of allocation of bubbles of hydrogen. After dissolution of the sample solution from the reservoir to the hydraulic valve attached to the main solution and wash the paddle 2−3 times with water.

To the solution was added with stirring in small portions of 1−1,5 g of sodium fluoride, after which the flask was closed again ground stopper with a water seal, and heating was continued. Fusion with acid potassium and copper is carried out according to the above method.

In a distillation flask washed through the funnel 2 pour 80 cmof sodium hydroxide solution mass concentration of 40 g/100 cm(you may use potassium hydroxide) through the funnel 3 to the sample solution, washing the flask to decompose the sample and the funnel with small portions of water, not allowing it to drain through. Increase the heating of the steam generator and conducted to distillation until the volume of distillate reaches 150 cm. The ammonia is captured by flask-receiver, filled with 25 cmof sulfuric acid solution with a molar concentration equivalent to 0.01 mole/DMand 25 cmof distilled water. At the end of the distillation to the solution in the receiver was added 1 cmof the indicator Tashiro, octarepeat excess of sulfuric acid with sodium hydroxide with a molar concentration equivalent to 0.01 mol/DMuntil a stable green color of the indicator. Under the same conditions conduct control experience to the content of nitrogen in the reaction

tiwah.

5.4.2 Determination of nitrogen on installation with air aspiration

Dissolution of the sample is carried out as specified in 5.4.1.

The vessel for trapping nitrogen in the case of direct titration poured 25 cmof the indicator solution Tashiro, in the case of reverse titration of 25 cmof sulfuric acid solution with molar concentration of equivalent of 0.01 mol/DM, 25 cmof distilled water and 1 cmof Tashiro indicator.

Further, in both cases in a distillation flask through a funnel with a tap poured 80 cmof sodium hydroxide mass concentration 40 g/cm(allowed the use of potassium hydroxide) and a sample solution, washing the flask to decompose the sample and the funnel with small portions of water, not allowing it to drain through. Close the valve of the funnel, include water-jet pump, a hot plate and heat the solution for 40 min.

In the direct titration as the flow of ammonia from the distillation flask into a vessel for trapping nitrogen, the color of the indicator Tashiro goes from purple-red to green. At the end of the distillation the liquid in the vessel octarepeat sulfuric acid solution with molar concentration of equivalent of 0.01 mol/DMto be stable for 5 min purple-red color.

In the case of reverse titration after distillation octarepeat excess of sulfuric acid with sodium hydroxide solution with molar concentration of equivalent of 0.01 mol/DMto a stable color indicator. Under the same conditions conduct control experience in the determination of nitrogen in the reagents.

When defining the endpoint of the titration is possible to use instrumental method

s.

5.5 processing of the results

5.5.1 Mass fraction of nitrogen , %, in the case of a reverse titration is calculated by the formula

(2)

where is the volume of sulfuric acid solution with molar concentration of equivalent of 0.01 mol/DMused for the capture of ammonia of the investigated samples, cm;

 — the conversion factor of the prepared sulfuric acid solution with molar concentration of equivalent of 0.01 mol/DM;

 — the volume of sodium hydroxide solution with molar concentration of equivalent of 0.01 mol/DMconsumed for titration of the excess sulfuric acid of a measured sample, cm;

 — coefficient of normality of the sodium hydroxide solution with molar concentration of equivalent of 0.01 mol/DM;

 — the volume of sulfuric acid solution with molar concentration of equivalent of 0.01 mol/DMused for the capture of ammonia in the reference experiment, cm;

 — the volume of sodium hydroxide solution with molar concentration of equivalent of 0.01 mol/DMconsumed for titration of the excess sulphuric acid in the reference experiment, cm;

0,00014 — the amount of nitrogen corresponding to 1 cmof sulfuric acid solution with molar concentration of equivalent of 0.01 mol/DM, g;

 — the weight of the portion,

Mass fraction of nitrogen , %, in the case of direct titration is calculated by the formula

(3)

where is the volume of sulfuric acid solution with molar concentration of equivalent of 0.01 mol/DMconsumed for titration of ammonia, cm;

 — the volume of sulfuric acid solution with molar concentration of equivalent of 0.01 mol/DMconsumed for titration of ammonia in the reference experiment, cm;

 — the conversion factor of the prepared sulfuric acid solution with molar concentration of equivalent of 0.01 mol/DM;

0,00014 — the amount of nitrogen corresponding to 1 cmof sulfuric acid solution with molar concentration of equivalent of 0.01 mol/DM, g;

 — the weight of the portion,

G.

5.5.2 Standards of accuracy and standards for monitoring the accuracy of determining the mass fraction of nitrogen should not exceed the values given in table 1.

Annex a (mandatory). Steel. The determination of nitrogen. A spectrophotometric method ISO 4945−77

APPENDIX A
(required)

A. 1 Scope

This standard specifies a spectrophotometric method for determining nitrogen in non-alloy and low-alloy steels when the mass fraction of from 0.002 to 0.050% when the mass fraction of silicon less than 0.6%.

A. 2 Normative references

In this standard, reference the following standard:

GOST 7565−81 Iron, steel and alloys. Methods of sampling for chemical analysis

A. 3 the essence of the method

The method is based on dissolution of steels in non-oxidising acids, decomposition of the formed ammonium salts with sodium hydroxide, distilling the ammonia with steam or air aspiration from the alkaline solution and its accumulation in an acidic environment. The formed complex compound, painted in blue color, measured spectrophotometrically at a wavelength of 640 nm.

A. 4 Reagents

A. 4.1 Distilled or deionized water that does not contain nitrogen compounds, purified in the secondary passing through the ion exchange resin.

A. 4.2 Potassium sulphate, anhydrous ().

A. 4.3 sulfuric Acid, = 1.84 g/cm, 96% solution (by weight).

A. 4.4 sulfuric Acid, = 1,21 g/cm, 29% solution (by weight).

200 cmof sulfuric acid (A. 4.3) is added in small portions during cooling to 700 cmof water (A. 4.1). The volume was adjusted with water to 1000 cmand mixed.

A. 4.5 sodium Hydroxide, approximately 12 n. solution.

480 g of sodium hydroxide dissolved in 700 cmof water, heated and boiled for 10 min, the volume was adjusted with water to 1000 cmand mixed. Store in a plastic container.

A. 4.6 sulfuric Acid, 1 n solution.

30 cmof sulfuric acid (A. 4.3) add to 700 cmof water, after cooling the volume was adjusted with water to 1000 cmand mixed.

A. 4.7 sulfuric Acid, to 0.04 n solution.

40 cmof sulfuric acid solution (A. 4.6) dilute with water to volume of 1000 cmand mixed.

A. 4.8 sodium Hydroxide, solution 0,2 n. a.

30 cmof sodium hydroxide solution containing 250 g/DM, diluted with water, the volume was adjusted with water to 1000 cmand mixed.

A. 4.9 Sodium phenolate: 5 g of phenol are added while stirring and cooling to a mixture of 10 cmof 250 g/DMsolution of sodium hydroxide and 80 cmof water. The volume was adjusted with water to 100 cmand mixed.

Prepare a solution during application.

A. 4.10 Sodium phosphate 12-water molar concentration of 0,1 mol/DM.

36 g 12-aqueous secondary sodium phosphate () was dissolved in water, the volume was adjusted with water to 1000 cmand mixed.

A. 4.11 pantaloonies Sodium ferrate (II) secondary dvuvodny (nitroprusside sodium), the solution of the mass concentration of 0.25 g/DM.

Nitroprusside 10 g of sodium is dissolved in water, the volume was adjusted with water to 1000 cmand mixed.

Before the definition of 25 cmof this solution was diluted with water to 1000 cmand mixed.

A. 4.12 Sodium hypochlorite, 0.1 N. solution (a 0.3 mass%).

Keep this solution at temperature not exceeding 10 °C.

A. 4.13 Nitrogen, a solution of mass concentration of 0.1 g/DM.

0,4716 g of dry ammonium sulphate is weighed to the nearest 0.1 mg, dissolve in water, transfer the solution into a flask with a capacity of 1000 cm, adjusted to the mark with water and mix. 1 cmof this solution to 100 mg of nitrogen.

A. 4.14 Nitrogen, a solution of mass concentration of 0.002 g/DM.

20 cmof ammonium sulphate solution is transferred to a flask with volume capacity of 1000 cm, adjusted to the mark with water and mix. 1 cmof this solution contains 0.2 mg of nitrogen. Prepare a solution during application.

A. 4.15 Methyl red, solution mass concentration of 0.1 g/DM.

0.1 g methyl red dissolved in water, transfer the solution into a flask with a capacity of 100 cm, the volume was adjusted to the mark with water and mix.

A. 5 Instrument

A. 5.1 diagram of the device for distillation without water vapor is shown in figure A. 1.

Figure A. 1 — Scheme of installation of the device for distillation without steam

1 — the heater 300 watts; 2 — round-bottom flask with a capacity of 500 cm; 3 — volumetric flask with
ground neck with a capacity of 100 cm

Figure A. 1 — Scheme of installation of the device for distillation without steam

A. 5.2 diagram of the device for distillation with steam is shown in figure A. 2.

Figure A. 2 — Scheme of installation of the device for distillation with steam

1 — a steam generator with a heating device; 2 — flask with a capacity of 1000 cm; 3 — hole; 4 — flask with a capacity of
500 cmremoval of distillate; 5 — drain tank; 6 — a flask with a capacity of 1000 cm; 7 — the collection (vessel) for
capture of nitrogen

Figure A. 2 — Scheme of installation of the device for distillation with steam

A. 5.3 Spectrophotometer

A. 6 Sampling and sample preparation

The selection and preparation of samples in accordance with GOST 7565.

A. 7 analysis

A. 7.1 Mounting the test sample

Sample tested sample mass 1 and 2 g is weighed to the nearest 0.001 g.

A. 7.2 Preparation of test solution

The sample is placed in a flask with a capacity of 150 cmadd 30 cmof sulfuric acid solution (A. 4.4), cover the watch glass and dissolved at a temperature of (85±5) °C until complete desorption of hydrogen.

After cessation of hydrogen evolution and remove watch glass and heat the flask until the appearance of white fumes of sulfuric acid. Then add 5 cmof sulphuric acid (A. 4.3) and 1 g of potassium sulfate (A. 4.2).

The mixture was heated for 2 h at temperatures above 300 °C so that it remains liquid.

Cool, add 10 cmof water and heated to dissolve the greater part of the sulphates.

A. 7.3 Distillation

Distillation is carried out with steam or without it.

A. 7.3.1 Distillation without steam

Installation diagram is shown in figure A. 1.

To collect distillate 5 cmof sulfuric acid solution (A. 4.6) is transferred into a flask with a ground neck with a capacity of 100 cm. Enter narrowed on the cone of the tubular continuation of the refrigerator in the flask so that it was immersed in a solution of sulfuric acid.

The analyzed solution is transferred to a distillation flask, washed with 60 cmof water, add 50 cmof sodium hydroxide solution (A. 4.5) and washed, the neck of the bulb 30 cmof water. The final volume of the solution should be 160−165 cm.

After adding sodium hydroxide, the flask is attached to the refrigerator. Distillation 80 cmof the solution is carried out for 25 min.

After distillation, washed the immersed tube with water, collecting the remains in a flask. The contents of the flask diluted to the mark with water and mix.

Get solutions for 1 g sample and 2 g of sample weight. The same operation is repeated for each sample to be examined.

Note — to adjust the boiling during distillation in the apparatus shown in the figure A. 1, it is desirable to add a few pieces of porous ceramics. These pieces pre-treated as a prototype, and is collected after distillation. Then they are washed with sulfuric acid (A. 4.6) until neutral, then with water and dried.

A. 7.3.2 Distillation with steam

Installation diagram is shown in figure A. 2.

To collect distillate 5 cmof sulfuric acid solution (A. 4.6) is transferred to a beaker of appropriate capacity, introducing him narrowed on the cone of the tubular continuation of the refrigerator, so that it was immersed in a solution of sulfuric acid (A. 4.7).

The analyzed solution is transferred to a distillation flask using a funnel. Wash the Kjeldahl flask 60 cmof water, add through the funnel 50 cmof sodium hydroxide solution (A. 4.5) and the funnel was washed with 30 cmof water. The volume of the solution should be 160−165 cm.

The steam generator should be pre-heated to begin the distillation immediately after the introduction of sodium hydroxide. Distillation 80 cmof the solution is carried out for 25 min. After distillation, washed the immersed tube with water, collecting the remains of a beaker.

The solution was transferred into a flask with a capacity of 100 cm, the volume was adjusted to the mark with water and mix. Get solutions for 1 g sample and 2 g of sample weight.

These operations are repeated for each sample to be examined.

A. 7.4 the development of the painting

In accordance with the proposed content of nitrogen take appropriate aliquote sample solutions and :

— 10.0 cmfor nitrogen from 0.020 to 0.050%;

— 25,0 cmfor nitrogen from 0.010 to 0.020%;

— 50,0 cm — nitrogen from 0.002 to 0,010% and transfer them to three volumetric flasks with a capacity of 100 cmeach.

Bring the volume with water to 50 cm. Add one drop of methylene red solution and neutralized with sodium hydroxide (A. 4.8.). Add in the bulb of the pipette in the following order: 5.0 cmof a solution of sodium phenolate, and 5.0 cmof a solution of secondary sodium phosphate, 10.0 cmof sodium nitropruside solution and 5.0 cmof sodium hypochlorite. The solutions in the flasks was adjusted with water to 100 cmand from time to time shake them well by inversion (10 times at least). The color of the solution becomes dark for 1 h at room temperature.

Note — These aliquote samples depend on the content of nitrogen. The content of nitrogen in the flask with a volume of 100 cmwhen the spectrophotometric measurement should be for the sample from 10 to 50 µg, from 20 to 100 µg, and their difference should be between 10 to 50 µg.

A. 7.5 Spectrophotometric measurement

Painted solutions and homogenizer and measure the optical density of the solution in cuvette with the thickness of the light absorbing layer 1 cm at a wavelength of 640 nm and the zero absorbance of the solution .

A. 7.6 Construction of calibration curve

A. 7.6.1 In six flasks with a capacity of 100 cmeach placed 0,0*; 5,0; 10,0; 15,0; 20,0 and 25,0 cmstandard solution of ammonium sulfate (mass concentration of nitrogen of 0.002 g/DM), which corresponds to 0; 10; 30; 40 and 50 µg of nitrogen.

____________

* Compensating solution.

Add to each flask 5 cmof sulphuric acid (A. 4.7) and the volume was adjusted with water to 50 cm. Add one drop of methylene red solution, neutralized with sodium hydroxide (A. 4.8) and continue the procedure described in A. 7.4.

A. 7.6.2 Spectophotometric measurement

Painted homogenizer solutions and measure the optical density of solutions in accordance with A. 7.5 at a wavelength of 640 nm in a cuvette with the thickness of the light absorbing layer 1 cm relative to the zero absorbing capacity of the compensating solution.

A. 7.6.3 Calculation of angle of slope of calibration curve

The results of optical density measurement and the nitrogen content (µg) build the calibration graph.

The angle of the constructed straight line characterizes the optical density of 1 g nitrogen in 100 cm.

A. 8 Handling of results

The content of nitrogen, relative mass units, is calculated by the formula

(A. 1)

where  — the ratio of the spectral absorbance of colored solutions corresponding to 1 and 2 g of sample to zero absorbance of the solution;

 — the inclination angle, the inverse of micrograms, calculated with respect to the optical path length of 1 cm;

 — volume alikvotnih sample solutions and taken from painted reactions, see;

the difference in mass between experimental samples and ,