GOST 12360-82

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  ГОСТ 12360-82

GOST 12360−82 Steel alloyed and high alloy. Methods of determining boron (Change No. 1)

GOST 12360−82

Group B39

STATE STANDARD OF THE USSR

STEEL ALLOYED AND HIGH-ALLOYED

Methods of boron determination

Steels alloyed and highalloyed.
Methods for the determination of boron

AXTU 0809

Date of introduction 1983−01−01

INFORMATION DATA

1. DEVELOPED AND INTRODUCED by the Ministry of ferrous metallurgy of the USSR

PERFORMERS:

N. P. Liakishev, Professor, corresponding member.; G. V. Kozina, candidate. chem. Sciences; R. D. Malinin, PhD. chem. science; N.And.Yelin, V. A. Belousov; Z. T. Kobozeva

2. APPROVED AND put INTO EFFECT by Decision of the USSR State Committee for standards from 29.01.82 N 381

3. REPLACE GOST 12360−66

4. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

5. Validity extended until 01.01.98* Decree of Gosstandart of the USSR from 1941 09.06.87 N
____________
* Expiration removed by Protocol No. 7−95 Interstate Council for standardization, Metrology and certification. (ICS, No. 11, 1995). — Note the CODE.

6. REVISED (June 1988) with amendment No. 1, approved in June 1987 (IUS 9−87)


This standard specifies the photometric, extraction-photometric methods for the determination of total mass fraction of boron (at a mass fraction of boron from 0.0005 to 0.1%) and the method of potentiometric titration to determine the total mass fraction of boron (at a mass fraction of boron from 0.05 to 2.0%) in the alloy and high-alloy steels.

1. GENERAL REQUIREMENTS

General requirements for methods of analysis GOST 20560−81.

2. THE PHOTOMETRIC METHOD FOR THE DETERMINATION OF BORON

2.1. The essence of the method

The method is based on the separation of boron in the form of bromatologia of the ether by distillation with methyl alcohol with subsequent formation of blue coloured compounds of boric acid with finalization in sulfuric acid solution. Light absorption of the solution measured at = 620 nm.

2.2. Apparatus, reagents and solutions

Distillation apparatus (see drawing) made of quartz or glass containing no boron. Allowed to use devices of other designs.

Spectrophotometer.

Sulfuric acid GOST 4204−77 and diluted 1:3. Before using acid cleaned 2−3 times distillation, adding 10 cmof methanol for every 250 cmacid. Distillation was carried out until the beginning of allocation of steams of sulfuric acid.

Orthophosphoric acid according to GOST 6552−80. Before using acid cleaned 2−3 times distillation, adding 10 cmof methanol for every 250 cmacid. Distillation was carried out until the beginning of allocation of vapors of phosphoric acid.

Hydrochloric acid by the GOST 3118−77.

Tin dichloride, the solution of 1 g of tin dichloride dissolved in 100 cmof hydrochloric acid.

Sodium hydroxide according to GOST 4328−77.

Hydrogen peroxide according to GOST 10929−76.

Potassium, anhydrous sodium carbonate according to GOST 4332−76.

Methanol according to GOST 6995−77.

An absolute standard.

Ginalization, solution: 0.12 g of finalizarea add 114 cmof water and sulfuric acid to 2 DM, the solution was stirred.

Boric acid according to GOST 18704−78 or GOST 9656−75.

The standard solutions of boron.

Solution a: 0,5720 g of boric acid dissolved in a small amount of water in a volumetric flask with a capacity of 1 DM, made up to the mark with water and mix.

1 cmof the solution contains 0.0001 g of boron.

Solution B: 50 cmsolution And transferred to a volumetric flask with a capacity of 1 DM, made up to the mark with water and mix.

1 cmof solution B contains 0,000005 g of boron.

Carbonyl iron according to GOST 13610−79.

Beads of glass or quartz, which does not contain boron.

Bidistilled water according to GOST 6709−72.

(Changed edition, Rev.

N 1).

2.3. Analysis

2.3.1. The weight and steel weight specified in the table. 1, is placed in the flask of the distillation apparatus, add 15−20 cmof sulfuric acid solution (1:3) or 10−15 cmof phosphoric acid. Connect the flask with a ground part of the device, such as a refrigerator and the contents gradually heated until complete dissolution of the sample.

After dissolution, the flask is removed and the solution was oxidized by adding dropwise 3−4 cmof hydrogen peroxide solution.

The flask is again connected with a device for distillation and boil the solution for 10−15 minutes, then cooled.

When the mass fraction of boron from 0.0005 to 0.04% for further analysis using the whole solution; for the mass concentration in excess of 0.04 to 0.10% solution from the flask is transferred to a volumetric flask with a capacity of 50 cm, made up to the mark with water, mix and aliquot part of this solution equal to 20 cm, transferred to a flask .

Table 1

Then add to the flask 15 cmof phosphoric acid, few quartz or glass beads and connect the flask with a device using pricereg sockets.

Stop the flow of water in the fridge , such as a refrigerator , using as receiver to the refrigerator graduated cylinder. The contents of the flask are heated until then, until peregonets all the water (to the consistency of the volume of the solution in a measuring cylinder).

After distillation of water from the flask , stop heating and include a fridge ; the fridge remains on. Distilled water, transferred quantitatively from a measuring cylinder of quartz glass or platinum Cup and save.

To a flask, measure 50 cmof methanol (allowed the use of Etalon), 7−8 cmof sodium hydroxide solution and add a few glass beads or quartz. In shutter pour 3 cmof sodium hydroxide solution. The flask is connected to a ground part of the device and the contents gradually heated until then, until half of the contents of the flask will not be distilled into the flask . Unplug the fridge , both flasks gradually heated for 50 min. the Entire Bor should be in the flask . Heating of the flask is stopped, from the flask distilled into the flask all the methanol, then cease heating the flask , such as a refrigerator , to a flask, add 0.5 g of potassium carbonate-sodium and sodium hydroxide solution from the shutter .

The flask is connected to a ground of the instrument and slowly heated, distilled, all methanol in the flask .

The residue of the flask are transferred quantitatively with distilled or deionized water in a quartz beaker or a platinum Cup.

The residue in the flask is treated as follows: the contents of the flask diluted with water to 250 cm, filtered through a dense filter paper mass of the filter with the possible residue is washed, transferred to a platinum crucible, gently dried and incinerated, added 0.5 g of anhydrous potassium carbonate-sodium and fused for 20 min. the Melt is leached 20 cmof phosphoric acid. The solution was transferred into the flask of the device and repeat the distillation process. The distillate obtained was joined to the solution in a quartz beaker or a platinum Cup and evaporated to dryness.

The dry residue in the quartz beaker or a platinum Cup leached 5 cmof water and 1.5 cmadded dropwise sulfuric acid. The resulting solution was transferred quantitatively into a measuring flask or graduated cylinder with a capacity of 10 cm, after cooling, is poured to the mark with water and mix.

The contents of the volumetric flask or graduated cylinder filtered through a dry filter into a dry beaker. In a flask with a capacity of 50 cmtransfer pipette 4 cmof the filtrate, add 0.2 cmof a solution of tin dichloride and with the help of a burette 40 cmsolution finalizarea. The contents of the flask was stirred, cooled and kept for 30 min and measure the absorption of the solution at a wavelength of 620 nm.

Solution comparison is the solution of the reference experiment.

A lot of find boron in the calibration schedule.

(Changed edition, Rev. N 1).

2.3.2. To build a calibration chart for six batches of iron with a mass of 1 g, placed successively into the flask , measure 1,0; 2,0; 4,0; 6,0; 8,0 and 10,0 cmstandard solution B; to the seventh charge is not added standard solution and perform control experience. The flask each time connect with a ground portion of the distillation device and come forth according to claim 2.3.1, with the exception of the processing of the insoluble residue.

The found values of optical density and corresponding values of the masses of the boron build the calibration graph.

(Changed edition, Rev. N 1).

2.4. Processing of the results

2.4.1. Mass fraction of boron () in percent is calculated by the formula

where is the mass of boron was found in the calibration schedule g;

 — the weight of the portion of the sample or portion of sample corresponding aliquote part of the solution,

2.4.2. Allowable absolute discrepancies in the results of parallel measurements at a confidence level = 0.95 does not exceed the values specified in table. 2.

Table 2

3. EXTRACTION-PHOTOMETRIC METHOD FOR THE DETERMINATION OF BORON

3.1. The essence of the method

The method is based on the conversion of boric acid in tetracarbonyl and extraction of 1,2-dichloroethane painted in blue connections tetrafluoroborate ions with the reagent methylene blue with subsequent measurement of light absorption of the extract at = 657 nm.

3.2. Apparatus, reagents and solutions

Spectrophotometer, photoelectrocolorimeter.

Hydrochloric acid by the GOST 3118−77 or GOST 14261−77.

Nitric acid GOST 4461−77 or GOST 11125−84.

Sulfuric acid GOST 4204−77, and the solution with molar concentration of equivalent of 2.5 mol/DM.

Hydrofluoric acid according to GOST 10484−78 and a solution with a mass concentration of 50 g/DM. To 20 cmhydrofluoric acid pour 150 cmof water and stirred. Stored in a vessel made of polyethylene.

Orthophosphoric acid according to GOST 6552−80, and diluted 1:1.

A mixture of hydrochloric and nitric acids, freshly made: to 150 cmof hydrochloric acid pour 50 cmof nitric acid and stirred.

A mixture of sulphuric and phosphoric acids: 180 cmorthophosphoric acid poured 20 cmof sulfuric acid and stirred.

Hydrogen peroxide according to GOST 10929−76 and diluted 1:1.

Potassium carbonate — sodium carbonate according to GOST 4332−76.

Potassium fluoride according to GOST 10067−80, a solution of 150 g of potassium fluoride dissolved in water, and dilute with water to 1 DM.

Stored in a vessel made of polyethylene.

Methylene blue solution: 3,739 g of methylene blue dissolved in water and diluted to 1 DM. 100 cmof the resulting solution is diluted with water to 1 DM.

1,2-dichloroethane according to GOST 1942−86. 1,2 — dichloroethane incubated with activated charcoal for two weeks.

Boric acid according to GOST 9656−75.

The standard solutions of boron.

Solution a: 0,5720 g of boric acid dissolved in a small amount of water in a volumetric flask with a capacity of 1 DM, made up to the mark with water and mix.

1 cmof the solution contains 0.0001 g of boron.

Solution B: 50 cmsolution And transferred to a volumetric flask with a capacity of 1 DM, made up to the mark with water and mix.

1 cmof solution B contains 0,000005 g of boron.

Carbonyl iron according to GOST 13610−79 and a solution of phosphoric acid: 25 g of iron carbonyl was placed in a quartz conical flask with a capacity of 500 cm, 300 cm pouredphosphoric acid diluted 1:1, and dissolved under moderate heating. The solution was cooled, poured dropwise hydrogen peroxide to complete oxidation of iron (about 60 cm), heat the solution to boiling and boil until the decomposition of hydrogen peroxide.

The solution was cooled, transferred to a volumetric flask with a capacity of 500 cm, was adjusted to the mark with water and mix. (To avoid salt precipitation water should be added in small portions and thoroughly mix the solution after each addition).

(Modified …

tion, Rev. N 1).

3.3. Analysis

3.3.1. Determination of boron in steel, soluble in sulphuric acid solution

3.3.1.1. A sample of steel weighing 0.25 g was placed in a quartz flask, poured 15 cmof sulfuric acid solution and closed ground quartz nozzle with reverse air refrigerator (quartz tube with a length of about 35 cm, internal diameter about 4 mm).

The contents of the vessel are heated at temperatures up to 150 °C with an air refrigerator to dissolve the sample. Then the solution was oxidized by adding dropwise through a condenser of 0.5−1.0 cmof hydrogen peroxide solution, the walls of the refrigerator should be rinsed with small portions of water and heating was continued for 5 min.

After cooling, remove nozzle, the refrigerator rinse with small portions of water and the sample solution was filtered through a dense filter with a paper weight in a plastic vessel with a capacity of 250 cm, which mark designating the amounts of 50 and 100 cm; the applied filtering funnel made of plastic. Allowed the use of platinum or quartz funnels. Filter the precipitate was washed several times with water, adding the washing liquid to the filtrate. The filter is transferred into a platinum crucible, gently dried and incinerated. The residue in the crucible is fused with 0.5 g of potassium carbonate-sodium carbonate at 700−800 °C, the melt leached with water and after cooling, attached to the main filtrate.

3.3.1.2. When the mass fraction in steel from 0.0005 to 0.005% of boron, obtained according to claim 3.3.1.1 solution is diluted with water to 50 cm, flow 10 cmof a solution of potassium fluoride, or 10 cmof a solution of hydrofluoric acid, mix and leave for 2 hours and allowed to leave the solution on longer, but no more than 1 day.

Then add by pipette 10 cmof methylene blue solution and made up to 100 cm. To a solution of a pipette, add 25 cmof 1,2-dichloroethane, the vessel is closed with a plastic cap, shaken for 60 s. Then transferred to a separatory funnel with a capacity of 150−200 cm, the organic layer (bottom) is transferred to a second funnel and washed by shaking with a precise 10 cmof water for 30 s. the Organic layer was filtered through a dry filter into a dry plastic beaker pipette select 5 cmof the filtrate into a measuring flask with a capacity of 25 cm, is diluted to the mark 1,2-dichloroethane, mix and measure the optical density of the solution on the spectrophotometer at a wavelength of 657 nm or photoelectrocolorimeter with a filter having maximum transmission in the wavelength range of 620−680 nm.

Solution comparison is the dichloroethane. Mass of boron in grams find the calibration schedule subject to amendments the reference experiment.

3.3.1.3. When the mass fraction of boron in the steel in excess of 0.005 to 0.1%, obtained according to claim 3.3.1.1 solution is transferred to a volumetric flask with a capacity of 100 cm, is diluted to the mark with water and mix.

In a plastic vessel poured aliquote part of this solution and the sulfuric acid solution according to table. 3.

Table 3

The solution in the plastic vessel is diluted with water to a volume of 50 cmand further arrive according to claim 3.3.1.2.

3.3.1.1−3.3.1.3. (Changed edition, Rev. N 1).

3.3.1.4. For construction of calibration curve seven quartz vessels were placed 0.25 g of steel similar in composition to the analyzed, but not containing boron, pour 15 cmof sulfuric acid solution and heated in a water bath until dissolved. The resulting solutions are oxidized by the addition of 0.5 cmof hydrogen peroxide solution, heating was continued for 5 min and after cooling transferred in plastic vessels with a capacity of 250 cm, which mark designating the amounts of 50 and 100 cm, add 0.5 g of anhydrous potassium carbonate-sodium in six vessels consistently measure 0,25; 0,5; 1,0; 1,5; 2,0; 3,0 cmstandard solution B. the Volumes of all solutions and top up with water to 50 cm, add 10 cmof a solution of potassium fluoride, or 10 cmof a solution of hydrofluoric acid to further conduct the analysis as described in section 3.3.1.2.

Solution not containing boron, is used for the reference experiment.

(Added, Rev. No. 1

).

3.3.2. Determination of boron in steel, insoluble in sulfuric acid.

Table 3A

The weight and steel weight in accordance with table. 3A is placed in a quartz glass with a capacity of 200 cm, 30 cm, pour themixture of hydrochloric and nitric acids, glass cover plastic cover and the sample is dissolved with moderate heating. Then pour 10 cmof a mixture of sulfuric and phosphoric acid and heat the solution until the appearance of sulphuric acid fumes. The solution was cooled, wash the lid and walls of glass with water and again evaporated to the appearance of sulphuric acid fumes. The solution was cooled, poured 40 cmof water, stirred and heated to dissolve the salts. The cooled solution is transferred to a volumetric flask with a capacity of 100 cm, doodat to the mark with water and mix. (To avoid salt precipitation water should be added in small portions and thoroughly mix the solution after each addition).

Aliquot part of the solution is 20 cmis placed in a polyethylene vessel with a capacity of 250 cm, poured a plastic beaker of 5 cmof a solution of hydrofluoric acid, mix and leave for at least 30 min. allowed to leave the solution on longer, but no more than 1 day. Then pour 10 cmof a solution of carbonyl iron, 20 cmwater, 5 cmof a solution of methylene blue, 25 cmof 1,2-dichloroethane, stirring the solution after each addition of the reagent. The vessel is closed with a plastic cap, shaken for 60 s. Then transferred to a separatory funnel with a capacity of 150−200 cm, the organic layer (bottom) was filtered through a dry filter or cotton in the dry glass with a capacity of 50 cm. Optical density of the solution measured on a spectrophotometer at a wavelength of 657 nm or photoelectrocolorimeter with a filter having maximum transmission in the wavelength range of 620−680 nm in a cuvette with a layer thickness of 10 mm.

Solution comparison is the dichloroethane.

Simultaneously conduct control experience for contamination of reagents.

A lot of find boron in the calibration schedule subject to amendments the reference experiment.

(Changed edition, Rev. N 1).

3.3.2.1. For construction of calibration curve seven quartz glasses with a capacity of 200 cmis placed sample of carbonyl iron in accordance with table. 4. Six glasses poured consistently 0,5; 1,0; 1,5; 2,0; 2,5; 3,0 cmstandard solution of boron B. the Seventh glass is used for the reference experiment.

All the glasses are poured 30 cmof a mixture of hydrochloric and nitric acids, beakers plastic cover caps and hinge are dissolved with moderate heating.

Then do as stated in claim 3.3.2. From the values of absorbance of analyzed solutions is subtracted the value of optical density in the reference experiment.

The found values of optical density of solutions and their corresponding mass values of boron in aliquote part of the solution to build calibration curve.

(Added, Rev. N 1).

3.3.3. (Deleted, Rev. N 1).

3A. The PHOTOMETRIC METHOD for the DETERMINATION of BORON IN STEELS WITH a MASS FRACTION of VANADIUM up to 1%

3A.1. The essence of the method

The method is based on formation of colored complex compounds of boron with Al-resorcinol and tioninom at pH 5.0 to 5.2 after separation of boron by sodium hydroxide in a strongly alkaline medium at pH 12−13. Light absorption of the solution measured at = 500−520 nm.

Tungsten and molybdenum do not interfere with the determination, the effect of aluminium can be eliminated by adding Trilon B.

3A.2. Apparatus, reagents and solutions

Spectrophotometer, photoelectrocolorimeter, pH meter.

The platinum crucible according to GOST 6563−75.

Sulfuric acid GOST 4204−77 or GOST 14262−78 and diluted 1:1.

Hydrochloric acid by the GOST 3118−77 or GOST 14261−77, solution with molar concentration of 6.0 mol/l, 1 mol/DM.

Nitric acid GOST 4461−77 or GOST 11125−78.

Orthophosphoric acid according to GOST 6552−80.

Acetic acid according to GOST 18270−72, solution with a molar concentration of 0.5 mol/DM.

Sodium hydroxide according to GOST 4328−77, solution with molar concentration of 5.0 mol/l, 1.0 mol/DM.

Rectified ethyl alcohol according to GOST 5962−67.

Disodium salt of ethylenediaminetetraacetic acid, 2-water (Trilon B) according to GOST 10652−73, solution with molar concentration of 0.05 mol/DM: 1,86 g Trilon B dissolved in 100 cmof water.

Ammonia water according to GOST 24147−80, solution with a molar concentration of 0.5 mol/DM.

Sodium carbonate according to GOST 83−79.

Carbonyl iron according to GOST 13610−79.

Al-resorcinol, disodium salt, solution with a molar concentration of 0.001 mol/DM: 0,0494 g, Al-resorcinol dissolved in 100 cmof water.

Tionin 2-water dye for microscopy, an alcoholic solution with a molar concentration of 0.001 mol/DM: 0,029 g thionine dissolved in 100 cmof ethanol.

Buffer solution: prepared by mixing equal volumes of acetic acid solution (0.5 mol/DM) and ammonia solution (0.5 mol/DM), then establish a pH of 5.0 to 5.2 on pH meter by addition of solutions of acetic acid or ammonia.

Boric acid according to GOST 9656−75.

The standard solutions of boron.

Solution a: 5,7154 g of boric acid are dissolved in 300 cmof water in a volumetric flask with a capacity of 1 DM, made up to the mark with water and mix.

1 cmof the solution contains 0.001 g of boron.

Solution B: 10 cmsolution And transferred to a volumetric flask with a capacity of 1 DM, made up to the mark with water and mix.

1 cmof solution B has the 0.00001 g of boron. Solution B is prepared before consumption.

Bidistilled water according to GOST 6709−72, additionally purified by passing through anion exchange resin AV-17 and KU-2.

3A.3. Analysis

3A.3.1. The weight and steel weight specified in the table. 3b is placed in a quartz glass with a capacity of 100 cm, flow 20 cmof a mixture of water, hydrochloric and nitric acids in the ratio 1:1:1, 2 cmof phosphoric acid, a glass cover plastic cover and the sample is dissolved with moderate heating.

Table 3b

If the sample is not soluble in this mixture for dissolution, a mixture of hydrochloric and nitric acids in the ratio 3:1 or 8:1 with the addition of 2 cmof phosphoric acid.

After dissolution, poured 8 cmdiluted 1:1 sulphuric acid and evaporated until the separation of weak sulphuric acid fumes.

Salt dissolved in 5 cmof hydrochloric acid, then pour the 30−40 cmof water and boil until complete dissolution of salts.

The insoluble residue is filtered through a dense filter, in a quartz glass with a capacity of 200 cm, a glass filter and washed several times with hot water. The filter is placed in a platinum crucible, burned, and calcined at 600−700 °C. the Residue in the crucible is fused with 1 g of sodium carbonate at 950−1000 °C for 15−20 min. the Melt is dissolved in hot water, adding 1−2 cmof hydrochloric acid and added to the main filtrate.

The combined solution was evaporated to 40−60 cm.

The solution is poured portions 60 cmof sodium hydroxide solution with molar concentration of 5 mol/DM.

For coagulation of the precipitate, the glass is put in a water bath for 30 min. solution and the precipitate was cooled, transferred to a volumetric flask with a capacity of 200 cm, made up to the mark with water, mixed and filtered in a dry quartz flask through the filter of medium density.

From the filtrate pipetted aliquot part of the solution for boron determination and placed in a beaker with a capacity of 50 cm, add 0.5 cmof the solution Trilon B (if the weight of aluminium in aliquote part of the solution than 0.25 mg, the volume of Trilon B is increased to 2.5 cm), water to 20 cmand with the pH-meter set pH 5.0 with hydrochloric acid initially, with a molar concentration of 6 mol/DM, and then 1 mol/lor sodium hydroxide solution with molar concentration of 1 mole/DM.

Then add exactly 5 cmof the solution Al-resorcinol and 1 cmof a solution of thionine with stirring, the contents of the beaker transferred to a volumetric flask with a capacity of 50 cm, the glass is rinsed with buffer solution, made up to the mark with buffer solution, and stirred for 18−24 hours, measure the optical density of the solution at = 500−520 nm relative to the control experiment conducted using the whole analysis.

When the mass fraction of boron of more than 0.005% of measurements taken after 2 hours.

A lot of find boron in the calibration schedule.

3A.3.1.1. For construction of calibration curve seven quartz glasses with a capacity of 100 cmplaced sample of carbonyl iron in accordance with the weight indicated in the table. 3b. Six glasses poured consistently 1,0; 4,0; 7,0; 10,0; 12,0; 15,0 cmstandard solution of boron B. the Seventh glass is used for the reference experiment.

All glasses poured 20 cmof a mixture of water, hydrochloric and nitric acids in the ratio 1:1:1, 2 cmof phosphoric acid, glasses cover plastic covers hitch and dissolved under moderate heating.

Then do as described in section 3A.3.1.

The found values of optical density of solutions and their corresponding mass values of boron in aliquote part of the solution to build calibration curve.

3A.4. Processing of the results

3A.4.1. Mass fraction of boron () in percent is calculated by the formula

where is the mass of boron was found in the calibration schedule g;

the weight of steel, suitable aliquote part of the solution,

3A.4.2. Allowable absolute discrepancies in the results of parallel measurements at a confidence level = 0.95 does not exceed the values specified in table. 2.

Sec. 3A. (Added, Rev. No. 1).

3.4. Processing of the results

3.4.1. Mass fraction of boron () in percent is calculated by the formula

where is the mass of boron was found in the calibration schedule g;

the weight of steel, suitable aliquote part of the solution,

3.4.2. Allowable absolute discrepancies in the results of parallel measurements at a confidence level =0.95 does not exceed the values specified in table. 2.

4. THE METHOD OF POTENTIOMETRIC TITRATION

4.1. The essence of the method

The method is based on the separation of boron from iron, Nickel, chromium, molybdenum and other elements of the alkali and barium chloride with subsequent determination of boron in the filtrate by the method of potentiometric titration. Before titration the pH of the solution set is 6.9, add mannitol or invert sugar and titrated the resulting complex acid with sodium hydroxide solution to the initial value of pH equal to 6.9.

4.2. Apparatus, reagents and solutions

The potentiometer (pH meter).

Electrodes: glass and calomel or silver chloride, attached to the potentiometer (pH-meter).

Stirrer.

Vessels made of quartz or glass containing no boron.

Hydrochloric acid by the GOST 3118−77 and diluted 1:1, 1:10.

Hydrogen peroxide according to GOST 10929−76, a solution with a mass concentration of 30 g/DMfreshly prepared.

Barium hydroxide according to GOST 4107−78, solution: 50 g of barium hydroxide dissolved in water and the solution diluted with water to 1000 cm.

Sodium hydroxide according to GOST 4328−77, 5; 0.1, and a solution with molar concentration of the equivalent 0,02 mol/DM.

A solution with molar concentration of the equivalent 0,1 mol/DMof sodium hydroxide: to 5000 cmof a solution containing 0.004 g/cmsodium hydroxide, poured 10−15 cmof a solution of barium hydroxide, stirred and allowed to settle upset during the day.

A solution with molar concentration of the equivalent 0,02 mol/DMsodium hydroxide: solution with molar concentration of the equivalent 0,1 mol/DMsodium hydroxide diluted with boiled during 1 h and cooled water in a ratio of 1:4 and stirred.

Set the mass concentration of the solution in a glass with a capacity of 400 cmis placed 5 to 10 cmof standard boron solution, pour 250 cmof water, lower the stirrer and the electrodes attached to the potentiometer. Result in rotation of the stirrer, pour a solution with molar concentration of the equivalent 0,1 mol/DMsodium hydroxide almost to pH 6.9, and then establish the exact value of pH = 6,9, priliva from burette a solution with molar concentration of the equivalent 0,02 mol/DMsodium hydroxide. The solution having pH = 6,9, poured 30 cmof a solution of mannitol or invert sugar (in this case the pH of the solution decreases) and titrated with a solution with molar concentration of the equivalent 0,02 mol/DMsodium hydroxide to the initial pH = 6,9.

Mass concentration of solution with molar concentration of the equivalent 0,02 mol/DMsodium hydroxide (), expressed in grams of boron per cubic centimeter, is calculated by the formula

where 0,0004 — concentration boron standard solution, g/cm;

 — the volume of a standard boron solution taken for titration, cm;

 — volume of solution with molar concentration of the equivalent 0,02 mol/DMof sodium hydroxide, spent on titration, sm;

 — volume of solution with molar concentration of the equivalent 0,02 mol/DMsodium hydroxide consumed for titration in the control experiment, cm.

Boric acid according to GOST 9656−75.

Standard boron solution: 2,288 g of boric acid dissolved in water in a volumetric flask with a capacity of 1000 cm, made up to the mark with water and mix.

1 cmof a solution containing 0.0004 g of boron.

D (-) Mannitol according to GOST 8321−74, saturated solution.

Sucrose GOST 5833−75.

Solution of invert sugar: 1 kg of sucrose are dissolved in 650 cmof water, poured 10 cmof hydrochloric acid (1:10) and heated for 2−3 h at 80−90 °C, then cooled and poured a solution with a mass concentration of 100 g/DMsodium hydroxide. The volume of alkali solution required to neutralize the hydrochloric acid, establish a preliminary titration of 10 cmof hydrochloric acid (1:10) solution with a mass concentration of 100 g/DMsodium hydroxide in presence of phenolphthalein indicator.

Potassium, anhydrous sodium carbonate according to GOST 4332−76.

Methyl orange, solution with a mass concentration of 1 g/DM.

Salt is the disodium Ethylenediamine-N, N, N', N' -tetraoxane acid (Trilon B) according to GOST 10652−73, 0.01 M solution.

Barium chloride according to GOST 4108−72, a solution with a mass concentration of 250 g/DM.

Phenolphthalein according to GOST 5850−72, solution in ethyl alcohol with a mass concentrat

iey 20 g/DM.

4.3. Analysis

The weight of steel depending on the mass fraction of boron is given in table. 4.

Table 4

The sample is placed in a conical flask with a capacity of 250 cmand 40 cm pourhydrochloric acid (1:1).

The flask is closed with a rubber stopper inserted in her selling a water refrigerator, the contents of the flask are heated to dissolve the sample, then pour 10−20 cmof hydrogen peroxide solution and boiled for 10 min, allowed dissolution of the sample at 100 °C without a refrigerator in the flask, closed the watch glass.

In case of incomplete dissolution of the sample solution is filtered through a dense filter with a paper weight. The filter residue is washed with hydrochloric acid (1:10) and hot water, adding the washings to the filtrate. The filter with precipitate was placed in a platinum crucible, dried, incinerated and the residue is fused with 0.5 g of anhydrous potassium carbonate-sodium at 900−950 °C. After cooling, the melt is leached 20−30 cmof hydrochloric acid (1:1) and attach the solution to the main filtrate.

The solution was transferred to a volumetric flask with a capacity of 500 cm, is diluted with water up to 200−300 cmand pour the sodium hydroxide solution with molar concentration of 5 mol/DMbefore the precipitation of hydroxides. The precipitated hydroxides were dissolved by adding dropwise hydrochloric acid (1:1), add 30−35cmof barium chloride, and after stirring 10−15 cmof sodium hydroxide solution with molar concentration of 5 mol/DM. The solution was then cooled, made up to the mark with water and mix. Part of the solution filtered through a dry filter into a dry volumetric flask with a capacity of 250 cm. In a glass with a capacity of 400 cm250 cm transferfilter carefully poured a solution of hydrochloric acid (1:1) until the color of methyl orange indicator and add 5 cmof a solution of Trilon B. the Contents of the glass boil for 3−5 minutes and cooled.

Into the beaker with the test solution is lowered stirrer and electrodes attached to the potentiometer. Result in rotation of the stirrer, pour a solution with molar concentration of the equivalent 0,1 mol/DMsodium hydroxide almost to pH 6.9, and then establish the exact value of pH = 6,9, priliva from burette a solution with molar concentration of the equivalent 0,02 mol/DMsodium hydroxide.

The solution having pH = 6,9, poured 30 cmof a solution of mannitol or invert sugar (in this case the pH of the solution decreases) and titrated with a solution with molar concentration of the equivalent 0,1 mol/DMsodium hydroxide to the source meant

Oia pH = 6,9.

4.1−4.3. (Changed edition, Rev. No. 1).

4.4. Processing of the results

4.4.1. Mass fraction of boron () in percent is calculated by the formula

where is the volume of sodium hydroxide solution consumed for titration, cm;

 — the volume of sodium hydroxide solution consumed for titration of the solution in the reference experiment, cm;

 — mass concentration of the sodium hydroxide solution, g/cm;

the weight of steel, suitable aliquote part of the solution, g

.

4.4.2. Allowable absolute discrepancies in the results of parallel measurements at a confidence level =0.95 does not exceed the values specified in table. 2.