GOST 26239.2-84

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  ГОСТ 26239.2-84

GOST 26239.2−84 semiconductor Silicon, the starting materials for its production and quartz. Methods of determining boron (Change No. 1)

GOST 26239.2−84

Group B59

STATE STANDARD OF THE USSR

SEMICONDUCTOR SILICON, THE STARTING MATERIALS FOR ITS PRODUCTION AND QUARTZ

Methods of boron determination

Semiconductor silicon, raw materials for its production and quartz. Methods of boron determination

AXTU 1709

Valid from 01.01.86
to 01.01.91*
_______________________________
* Expiration removed
Protocol N 7−95 Interstate Council
for standardization, Metrology and certification
(IUS N 11, 1995). — Note the manufacturer’s database.

DEVELOPED by the Ministry of nonferrous metallurgy of the USSR

PERFORMERS

Y. A. Karpov, M. N. Schulepnikov, M. K. Vinnikov, G. G., Gavin, N. Gradskova, O. V. Zavialov, T. I. Zyablova, V. E., Quinn, V. A. Krylov, A. I. Kuzovlev, N. And. Marunya, V. G., Miscreants, V. M. Mikhailov, M. G. Nazarova, V. A. Orlov, A. I. Stepanov, N. With. Sysoeva, V. I. Firsov, G. I. Alexandrova

INTRODUCED by the Ministry of nonferrous metallurgy of the USSR

Member Of The Board Of A. P. Snurnikov

APPROVED AND put INTO EFFECT by Decision of the USSR State Committee on standards dated July 13, 1984 N 2490

The Change N 1, approved and in effect as of 01.01.91 by the resolution of Gosstandart of the USSR from 26.06.90 N 1847

Change No. 1 made by the manufacturer of the database in the text IUS N 2, 1990


This standard specifies the chemical-atomic emission method for the determination of boron in semiconductor silicon in the range of mass fraction from 2·10to 2·10% in silicon dioxide and quartz from 1·10to 1·10%, cetarehhloristam silicon and trichlorosilane from 6·10to 7·10% and atomic-emission method for the determination of boron from 0.001 to 0.1% in technical silicon.

(Changed edition, Rev. N 1).

1. GENERAL REQUIREMENTS

1.1. General requirements for methods of analysis GOST 26239.0−84.

2. THE CHEMICAL-ATOMIC EMISSION METHOD FOR THE DETERMINATION OF BORON

______________
* The name of the section. Changed the wording, Rev. N 1.

The method is based on the preconcetration of boron by removing the core element of silicon in the form of tetrafluoride in the analysis of semiconductor grade silicon, silicon dioxide, quartz and in the form of tetrachloride-tetrafluoride in the analysis of silicon tetrachloride and trichlorosilane in the presence of mannitol, which forms a semi-boron complex compound, and the spectral analysis of the concentrate of boron on the graphite powder with the addition of PTFE.

2.1. Apparatus, materials and reagents

The diffraction type spectrograph DFS-8 with the grating 600 gr/mm with two-lighting system (lens F-75 25 mm in diameter) or spectrograph medium dispersion type of ISP-28 with a three-lens Achromat lighting system.

The arc generator type DG-2 with an additional variable resistor, adapted for ignition of the arc DC high-frequency discharge.

Rectifier 250−300, 30−50 A.

Microphotometer geregistreerde type MF-2.

Spectromancer type SPP-2.

Analytical scale.

Libra torsion.

Mortar and pestle made of organic glass.

Grinding machine graphite electrodes.

Electrodes graphite fittings for spectral analysis high purity-7−4, 6 mm in diameter, sharpened to a cone; or graphite electrodes, machined from high purity graphite rods-7−3, 6 mm in diameter, sharpened to a cone with an apex angle of 15° and a platform with a diameter of 1.5 mm at the tip, burnt in the arc of direct current at 15 And during 15 s.

Electrodes graphite fittings for spectral analysis high purity-7−4, with a diameter of 6 mm, channel depth of 6 mm with a diameter of 4 mm; or graphite electrodes of the same size, machined from high purity graphite rods-7−3, burnt in the arc of direct current at 15 And during 15 s.

Cleaning firing is subjected to each pair of electrodes before measurement (electrode, sharpened to a cone — cathode, the electrode with the channel / anode). Mass fraction of boron in graphite electrodes should be less than 1·10%.

Graphite powder OS.h. 8−4 according to GOST 23463−79.

Lamp infrared ikz-500 with voltage regulator type RNO-250−0,5.

Box with organic glass type 8БП1-OS for sample preparation to spectral analysis.

Box of organic glass with purified through the fabric Petryanov air for chemical preparation of samples 2БП2 type-OS.

Electric tile with a surface temperature of not more than 105 °C.

Cylinders made of organic glass 10 and 25 cm.

Devices made of organic glass for sample preparation to spectral analysis (stands for graphite electrodes, spatulas, nabuaki).

Drying Cabinet, providing a heating temperature of 250 °C.

PTFE Cup with a capacity of 20 and 100 cm.

The PTFE beakers with screw-caps, with a capacity of 20−25 cm, and 75−80 cm.

Cups with lids of glassy carbon and Teflon with a capacity of 25−30 cm.

Photographic records of type 2, ensure the normal blackening of analytical lines of boron and the surrounding background in the spectrum.

Nozzle with a slot height 5 mm, worn on the slit of the spectrograph DFS-8.

Hydrofluoric acid OS.h. 27−5.

Nitric acid of high purity according to GOST 11125−84 or nitric acid H. h according to GOST 4461−77, double-distilled in quartz apparatus.

Hydrochloric acid by the GOST 3118−77, H. h., or hydrochloric acid of high purity according to GOST 14261−77, distilled in Teflon device (before distillation of the hydrochloric acid is diluted with deionized water in the ratio 1:1), 6 M solution.

Water deionized with a specific resistivity of 10−20 Mω·cm.

D (-) Mannitol according to GOST 8321−74, spectral pure according to Bohr, 1 and 10% solutions.

Teflon-powdered 4 according to GOST 10007−80.

The technical rectified ethyl alcohol GOST 18300−87.

The drill according to GOST 8429−77, a standard solution containing 1 mg/cmboron: 0,882 g of borax dissolved in a little water. The resulting solution was transferred to a volumetric flask with a capacity of 100 cm, adjusted to the mark with water and mix.

The sodium fluoride.

Autoclave analytical M 167 with a reaction chamber M 206; 3551 with a reaction chamber With 3552 in accordance with the Annex to GOST 26239.1−84.

(Changed edition, Rev. N 1).

2.2. Preparation for assay

2.2.1. Sample preparation comparison (OS)

2.2.1.1. The main reference sample (OOS) with a mass fraction of boron 0,1%: in Teflon Cup with a capacity of 50 cmis placed 0,999 g of graphite powder, pour 1 cmof a standard solution of borax containing 1 mg/cmboron. The mixture was thoroughly stirred and dried under an infrared lamp at a temperature not higher than 80 °C. the Dried mixture was thoroughly stirred PTFE pestle for 40 min.

2.2.1.2. References OC1-ОС7 prepare serial dilution of the main sample comparison of CEO, and then each subsequent reference sample graphite powder in the presence of ethanol. Mass fraction of boron in the samples comparison OC1-ОС7 (in percent, based on the content of boron in the mixture of boron and carbon) and added to the mixture of sample graphite powder and diluted sample, mixing for this sample are given in table.1.

Table 1

Given sample of graphite powder and diluted sample was placed in a mortar made of organic glass, pour 1 cmof a 10% solution of mannitol. The mixture was thoroughly stirred and dried under an infrared lamp at a temperature not higher than 80 °C. the Dried mixture was thoroughly stirred PTFE pestle for 40 min.

Each reference sample (OS) from the OC1-ОС7 placed in a mortar made of organic glass, add 2 cmof a 10% solution of mannitol, and thoroughly mixed and dried under an infrared lamp at a temperature not higher than 80 °C.

All operations on preparation of samples of the comparison performed in box organic glass, carefully wiping the walls of the Boxing pieces of calico, soaked in ethanol.

In the analysis of use (taking pictures of spectra) ОС3-ОС7.

The samples of the comparison is stored in tightly closed cans of organic glass.

2.2.1.1, 2.2.1.2. (Changed edition, Rev. N 1).

2.2.2. Sample preparation of silicon and quartz to analyze

Samples of silicon or quartz is washed with concentrated hydrochloric acid when heated, and then deionized water and dried. The washed pieces are wrapped in clean plastic wrap and smash wrapped in plastic wrap with a hammer into pieces the size of 1−3 mm.

2.3. Analysis

2.3.1. The concentration of boron

2.3.1.1. To obtain a concentrate of boron in the analysis of semiconductor grade silicon

A portion of the silicon mass of 1 g was placed in Teflon beaker with a screw cap with a capacity of 20−25 cm, flow 0.2 cm1% solution of mannitol and 9 cmhydrofluoric acid. The contents of the Cup mix well and add cold carefully dropwise 3.5 cmof nitric acid. Adding each subsequent drop of nitric acid the lead after the cessation of rapid allocation of nitrogen oxides, covering each time the glass lid. The bulk silicon is dissolved. After that, the glass close screw cap, placed into another Teflon beaker with a screw. cover with a capacity of 75−80 cm, close the screw cap and put in a drying Cabinet for 1 h at a temperature of from 80 to 90 °C (during this time, the portion of the silicon is completely dissolved). The dissolution of silicon may be performed also in cups with lids of glassy carbon on the hot plate at a temperature of from 80 to 90 °C.

After complete dissolution of silicon in the solution is quantitatively transferred into a Teflon Cup with a capacity of 20 cm, add 20 mg of graphite powder was mixed thoroughly by rocking the Cup and evaporated to dryness on a hotplate at a temperature of from 80 to 90 °C. To the dry residue add 2−3 times in 0.5 cmof a mixture of hydrofluoric and nitric acids (1:1), evaporated each time to dryness. The dry residue from the Cup was transferred to a bag made of paper with a spatula.

The obtained dry residue is a concentrate of boron subjected to atomic-emission analysis.

All work associated with the concentration of boron is carried out in a box of organic glass with purified through the fabric Petryanov air, wiping the walls of the Boxing pieces of calico, soaked in ethanol.

Analysis of each sample of silicon is carried out from three parallel batches.

At the same time through all stages of the analysis carried out three follow-up experience for contamination of reagents and get three dry residue three concentrate boron in the reference experiment.

Allowed to obtain a concentrate of boron in the analytical autoclave directly in the crater of the graphite electrode.

Analysis of each sample of silicon is carried out from three parallel batches. For this purpose, the 3 craters of graphite electrodes with nozzles placed sample of silicon with a mass of 0.5 g (or 1 electrode with a suspension of 1.5 g) mixed with 20 mg of graphite powder and 1 mg of powdered Teflon, dipped to 0.02 cmof a 10% solution of mannitol.

At the same time through all stages of the analysis carried out three follow-up experience for contamination of reagents.

The electrodes with the samples and control experiments was placed in a Teflon electrode holder. The electrode holder is placed in a glass reaction chamber, which is poured 35 cmhydrofluoric and 5 cmof nitric acid.

Reaction chamber placed in the housing of the autoclave, seal it, put into an oven and allowed to stand for four hours at 200−220 °C.

After that, the autoclave is removed from the oven, cooled with a fan or contact of the refrigerator. After opening the autoclave, the reaction chamber wipe the outside with a cotton swab moistened with alcohol. Take out the electrodes and, if necessary, dried them under a heat lamp.

Concentrates impurities in the electrodes is subjected to atomic-emission analysis.

(Changed edition, Rev. N 1).

2.3.1.2. To obtain a concentrate of boron in the analysis of silicon dioxide and quartz

A sample of silicon dioxide or quartz with a mass of 2 g is placed in a Teflon beaker with a screw cap with a capacity of 20−25 cm(for analysis of silicon dioxide the sample moistened with 0.5 cmdeionized water), add 0.2 cm1% solution of mannitol, poured 8 cmhydrofluoric acid, cover the beaker with screw cap and placed into another Teflon beaker with a screw cap with a capacity of 75−80 cm. Close the glass screw-on lid and put in the oven for 1−2 hours at a temperature of from 80 to 90 °C (during this time, the suspension of silicon dioxide or quartz is completely dissolved). The dissolution of silicon dioxide (quartz) may be performed also in Teflon cups with lids on the hotplate at a temperature of from 80 to 90 °C. After complete dissolution the solution was quantitatively transferred into a Teflon Cup with a capacity of 20 cm, add 20 mg of graphite powder and evaporated to dryness on a hotplate at a temperature of from 80 to 90 °C. To the dry residue add two times with 0.5 cmhydrofluoric acid, evaporating to dryness each time.

Then continue as described in section 2.3.1.1

.

2.3.1.3. To obtain a concentrate of boron in the analysis of silicon tetrachloride and trichlorosilane

In a Teflon Cup with a capacity of 100 cmis placed 0.2 cm1% solution of mannitol, poured 33 cm(50 g) silicon tetrachloride or 37 cm(50 g) of trichlorosilane, selected plastic cylinder, and stirred for 2 minutes, the Cup with the contents was placed in a box with clean through the fabric Petryanov air and leave for the Stripping of silicon by natural evaporation in the form of tetrachloride, trichlorosilane. The silicon dioxide resulting from partial hydrolysis due to moisture in the air, dissolve by adding 5−7 cmhydrofluoric acid and 20 mg of graphite powder put on a hot plate for the distillation framework in the form of tetrafluoride-silicon tetrachloride and evaporated to dryness at a temperature of from 80 to 90 °C To the dry residue add 0.5−1 cmhydrofluoric acid and evaporated to dryness. This operation is carried out two more times, each time evaporating to dryness. Further still, as shown by V. p.2.3.1.1.

2.3.2. Atomic emission analysis concentrates

2.3.2.1. To each concentrate obtained from a test sample or in a Supervisory experience, and 20 mg each of the samples of comparison ОС3-ОС7 add 1 mg of powdered PTFE (or 1 mg of sodium fluoride) and gently stirred with a spatula on a piece of tracing paper, carefully wiping the spatula and kick ball after each sample pieces of calico, soaked in ethanol. Each mixture with the fluoropolymer are placed in the channel of the graphite electrode with a diameter of 4 mm and a depth of 6 mm, and a mixture of sodium fluoride into the channel of the electrode with a diameter of 4 mm and a depth of 3 mm. So get three electrodes with concentrates one of the samples, three electrode concentrates the three control experiments, the three electrode samples comparison ОС3, etc. electrode with a concentrate of impurities (or the reference) serves as the anode (lower electrode). The upper electrode is a graphite electrode, sharpened to a cone. Between the electrodes ignite the arc DC power 10 (or 15 And the use of sodium fluoride). The spectra are photographed on diffraction spectrograph DFS-8 spectrograph, or on the average variance of ISP-28.

When photographing spectra in the spectrograph DFS used two-lighting system (used the lens F-75 with a diameter of 25 mm). The slit of the spectrograph put a nozzle with a slit height of 5 mm. Scale wavelengths set at 280 nm. In the cassette load plate type 2. The width of the slit of a spectrograph 15 microns. The exposure time is 10 s (about 30 s, before fading, when using sodium fluoride). During exposure the distance between the electrodes is maintained at 3 mm.

When photographing spectra in the spectrograph ISP-28 are being used the lighting system. Intermediate diaphragm 5 mm. the Width of the slit of a spectrograph 15 microns. Exposure time 10 s (or 30 s, before fading, when using sodium fluoride). During exposure the distance between the electrodes is maintained at 3 mm. In the cassette loading plates type 2.

2.3.1.3, 2.3.2, 2.3.2.1. (Changed edition, Rev. N 1).

2.3.2.2. In the same conditions photographed three times the range of concentrates of the analyzed samples, the range of concentrates obtained from control experiments, and the range of each of the samples of the comparison.

Exposed photographic exhibit, washed with water, fixed, washed in running water for 15 min and dried.

2.4. Processing of the results

2.4.1. The final result of the analysis taking the geometric mean of results of three parallel measurements, each made from a separate sample of semiconductor silicon, silicon dioxide, quartz, silicon tetrachloride or trichlorosilane.

2.4.2. In each spectrogram photometric blackening of analytical lines of boron (use a line of boron In 249,77 nm) and nearby background (minimum blackening near the analytical line of boron from either side, but with the same in all spectra taken on one disc) and calculate the difference pucherani . On three values , , obtained three spectrograms taken for each sample, find the arithmetic mean . From the obtained average values are transferred to corresponding values of the logarithms of relative intensity given in the mandatory Annex GOST 13637.1−77*.
______________
* On the territory of the Russian Federation the document is not valid. Standards 13637.1−93, here and hereafter. — Note the manufacturer’s database.

Values and comparison of samples for build calibration curve in the coordinates ; the value for concentrates control experiments determine the average value of the mass fraction of boron concentrates in the control experiments. Accordingly, the value for concentrates of the sample find the schedule for the calibration the mean value of mass fraction of boron in concentrates analiziruet

my sample.

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

,

where is the mass of the sample graphite powder collector, g;

 — the weight of the portion of semiconductor silicon, silicon dioxide, quartz, silicon tetrachloride or trichlorosilane, g;

the average value of the mass fraction of boron in the concentrates of the sample, %;

the average value of the mass fraction of boron concentrates in the reference experiment, %.

The value should not exceed the established for the method the lower limit of the determined values of the mass fraction of boron is more than two times. If this condition is not ensured, should be carefully phased in to clean the room, jobs, used equipment, reagents and materials.

2.4.4. While monitoring convergence results of parallel measurements of the three values , , obtained three spectrograms taken for the three concentrates of the sample, select the largest and smallest values, pass them to the corresponding values of and are given in mandatory Appendix GOST 13637.1−77, and find the corresponding values of mass fraction of boron in the sample and

.

2.4.5. The ratio of the highest of the three results of parallel measurements for the smallest with confidence probability of 0.95, should not exceed the values of permissible differences of the three results of the parallel definitions are given in table.2.

Table 2

(Changed edition, Rev. N 1).

2.4.6. Control of the correctness analysis is carried out by additives. For this solutions in three parallel batches of semiconductor silicon (or three parallel hinges of silicon dioxide, quartz, silicon tetrachloride or trichlorosilane) with a minimum value of the mass fraction of injected boron Supplement boron in the form of a solution of borax (see p. 2). The agent is added in such an amount in which the value of the mass fraction of boron in the sample with the additive were no less than three times the value of the lower boundary value of mass fraction of boron by the method, is not less than the tripled value of mass fraction of boron in the sample and not more than the upper boundary of the determined values of the mass fraction of boron by the method. Samples with the addition of analyze in sect.4 and 5.

The result of the analysis you think is right with confidence probability of 0.95, if the allowable discrepancy between the results of the analysis of samples with the additive and its computed value (where the result of analysis of the sample,  — the mass fraction of additives) does not exceed the values given in table.3.

Table 3

Note. Determination of boron in semiconductor silicon, silicon dioxide and quartz can also be performed according to GOST 26239.1−84 together with the metallic impurities. Joint chemical-atomic-emission determination of metallic impurities and boron is carried out according to GOST 26239.1−84. As the carrier use combined medium — sodium chloride plus polytetrafluoroethylene (1 mg) or sodium chloride plus sodium fluoride (1 mg).

For the preparation of the joint core reference sample (OOS) of metallic impurities and boron, prepared according to GOST 26239.1−84 EP on metal impurities enter the calculated amount of boron in the form of borax solution according to claim 3.1.1.

For sample preparation comparison OC1-ОС7 every once in a mortar made of organic glass, before mixing the portions of the graphite powder and the diluted sample comparison, pour in 1 cmof a 10% solution of mannitol.

Processing of the results of the analysis carried out according to GOST 26239.1−84 (sect.5).


(Changed edition, Rev. N 1).

3. ATOMIC-EMISSION METHOD FOR THE DETERMINATION OF BORON

______________
* The name of the section. Changed the wording, Rev. N 1.

The method is based on the excitation spectrum in the arc AC. The boron content is determined according to the calibration schedule, constructed in the coordinates: the difference pucherani analytical lines and background () is the logarithm of the boron concentration ().

3.1. Apparatus, materials and reagents

The quartz type spectrograph ISP-28 with a three-lens Achromat lighting system.

The arc generator type DG-2.

Microphotometer type MF-2.

Analytical scale.

The machine tool for sharpening of electrodes.

The copper electrodes of 6 mm in diameter, sharpened to a cone with a diameter of pad 2 mm.

The copper electrodes of 6 mm in diameter, with a channel depth of 6 mm and a diameter of 4 mm.

Mortar agate or titanium.

Hot plate with thermostat or sand bath.

Silicon with a boron content of 1·10%.

The drill according to GOST 8429−77.

Solution of borax containing 5 mg cmboron: 4,412 g of borax is dissolved in water, and dilute with water to 100 cm.

Plate photographic UPS or 3 for normal blackening of analytical lines and the surrounding background in the spectrum.

The technical rectified ethyl alcohol GOST 18300−87.

(Changed edition, Rev. N 1).

3.2. Preparation for assay

3.2.1. Sample preparation comparison (OS)

The main reference sample (OOS) with a mass fraction of boron 1%: 1.0 g of finely ground in a mortar silicon moisten with 2 cmof borax solution. The wetted powder is dried on a sand bath and stirred in a mortar for 2 hours.

References OC1-ОС7 prepare serial dilution of the main sample comparison of CEO, and then each subsequent sample of the silicon powder.

Mass fraction of boron in the samples comparison OC1-ОС7 (in percent, based on the content of boron in silicon) and added to the mixture of the silicon sample and diluted sample, mixing for this sample are given in table.4.

Table 4

Listed in the table.4 sample of silicon and of diluted sample was placed in a mortar and thoroughly triturated with ethyl alcohol for 30 min and dried under an infrared lamp.

The comparison samples stored in closed jars or packages.

3.3. Analysis

Received for analysis a portion of the silicon triturated in a mortar to a state of powder.

The crushed sample and each reference sample is placed in the channel of the lower electrode. The upper electrode is a copper electrode, sharpened to a cone.

Between the electrodes ignite the arc of an alternating current power of 10 A. the Spectra are photographed on the type of spectrograph ISP-28 being the illumination system of the slit. The iris is fully open. The time of exposure was 20 s. During the exposure, the distance between electrodes 3 mm Slit of the spectrograph 0.0015 mm. In the cassette load plate UFS or type 3.

In the same conditions photographed three times the spectra of the analyzed samples and the spectra of each reference sample.

Exposed photographic exhibit, washed with water, fixed, washed in running water for 15 min and dried.

3.4. Processing of the results

3.4.1. In each spectrogram photometric blackening of analytical lines of boron 249,77 nm and the surrounding background (minimum blackening from the shorter wavelengths) and compute the difference pucherani .

On three values , , obtained three spectrograms taken for each sample, find the arithmetic mean .

Values and comparison of samples for build calibration curve in the coordinates ; the value for the analyzed samples, find the average content of boron in

sample.

3.4.2. While monitoring convergence results of parallel measurements of the three values , , obtained three spectrograms, select the largest and smallest values and find the corresponding boron content in the sample.

3.4.3. Allowable absolute differences of the results of three parallel definitions should not exceed the values given in table.5.

Table 5

3.4.4. The checking is carried out by additives. To do this, three parallel batches of silicon with a minimum content of boron is injected additive of boron in the form of a solution of borax, which is prepared from the primary reference sample (OOS). The agent is added in such amount that the boron content in the sample with the additive were no less than three times the value of the lower boundary of the designated contents is not less than tripled boron content in the sample and not more than the upper boundaries of the content according to the method. Sample with the addition of analyze in accordance with sec. 4, 5.

The results of the analysis you think is right with confidence probability of 0.90 if the difference of the results of the analysis of the sample with the additive and the calculated content of the sample with the additive does not exceed the values of permissible differences of the two analyses are given in table.6.

Table 6

4. EXTRACTION-SPEKTROFOTOMETRICHESKOE METHOD FOR THE DETERMINATION OF BORON

The method is based on dissolving of silicon with a mixture of hydrofluoric and nitric acids in the presence of mannitol, the removal of the bulk silicon transport in the form of fluoride, tetrafluoroborate ion extraction with butylamine toluene and subsequent spectrophotometric determination of boron.

4.1. Apparatus, reagents and solutions

The spectrophotometer SF-26 or similar.

Cuvettes for photometry with the optical path length of 50 mm.

Laboratory scales.

Tiles electric appliances GOST 14919−83.

Drying Cabinet with temperature control temperature up to 250 °C.

Autoclave analytical M 167 with a reaction chamber 206 M, 3551 with a reaction chamber With 3552 application-26239.1 GOST-84.

The indoor fan type VE-6 or similar.

Microburette 7−2-10 according to GOST 20292−74*.
________________
* On the territory of the Russian Federation the document is not valid. There are 29169−91 GOST, GOST 29227−91−29229−91 GOST, GOST 29251−91-GOST 29253−91. — Note the manufacturer’s database.

Volumetric flasks with a capacity of 25, 100 and 1000 cm.

Pipettes with a capacity of 1, 2, 5 and 10 cm.

The glassy carbon crucibles with a capacity of 50 cm.

The PTFE cylinders with a capacity of 20 cm.

Plastic piston pipettes with a capacity of 5 and 10 cm.

Sulfuric acid of high purity according to GOST 14262−78.

Hydrofluoric acid on the other 6−09−3401−88, OS. h 27−5, density 1.2 g/cm.

Nitric acid of high purity according to GOST 11125−84, density 1.4 g/cm.

Hydrochloric acid density of 1.19 g/cmOS.h 21−4.

Mannitol according to GOST 8321−74, spectral pure according to Bohr, 1% solution.

The technical rectified ethyl alcohol GOST 18300−87.

Formaldehyde on the other 6−09−3011−73, 40% solution (formalin).

Butylamine on the other 6−09−05−504−76, a 0.1% alcoholic solution.

Acetone according to GOST 2603−79.

Toluene on the other 6−09−4305−76.

Boric acid according to GOST 9656−75.

Water deionized with a specific resistivity of 10−20 mω·cm.

The standard solutions of boron

Solution a containing 0.1 mg of boron per 1 cm: hitch weight 0,5720 g of boric acid dissolved in deionized water in a volumetric flask with a capacity of 1000 cm.

Solution B containing 0.01 mg of boron per 1 cm: prepared on the day of use by dilution of a standard solution And with water 10 times.

4.2. Analysis

4.2.1. Dissolution of a test portion in an open system

A sample weighing 0.25 g was placed in a crucible of glassy carbon, poured 0.1 cmof a solution of mannitol, 5 cmhydrofluoric acid, mix. Then gently, to prevent violent reaction, dropwise introduced 1 cmof nitric acid (1:1). The crucible with the solution is placed on the tile and is evaporated to wet salts and then to dryness in a water bath, add 5 cmhydrofluoric acid and again evaporated to dryness.

4.2.2. Dissolution of the sample in the analytical autoclave

B reaction tank (2) on the application of GOST 26239.1−84 with a capacity of 70 cmpour 10 cmhydrofluoric and 5 cmof nitric acid. Collection (1), in which is placed a portion of sample weighing 0.25 g and 0.1 cmof a solution of mannitol, coaxially placed in the reaction vessel (2). Two-compartment reaction container with the contents is closed with the lid (4) and sealed in a metal enclosure of the autoclave (1, 5). For this, rotating clockwise one turn tension nut (7), pull locking device (6), housing cover (5) wrapped around the housing (1) until it stops. After that the tension nut (7) turn counterclockwise until it turns freely. Sealed autoclave was placed in a preheated to 180 °C drying cupboard and allowed to stand for 2 hours, remove from oven and cool on bottom refrigerator (8) to room temperature. Autoclave razgermetizatsii by rotating the tensioning nut (7) clockwise until housing cover of the autoclave (5) rotates freely on the thread of the housing (1). Open the autoclave and remove the reaction chamber (2, 4).

For sample preparation of multiple batches simultaneously in a single hermetically closed space is used With autoclave 3551 with the camera to concentrate With 3552 (or similar).

In the reaction chamber for concentrating (1) 35 cm pourhydrofluoric and 5 cmof nitric acid. Three fluoropolymer collector (4) mounted in the holder (2) placed the sample sample weighing 0.25 g each, were added to the test portions of 0.1 cmof a solution of mannitol and 0.5 cmhydrofluoric acid. The camera focus is closed with the lid (5) with a holder (2) and collectors (4) and sealed in a metal casing analytical autoclave. The autoclave was placed in a preheated drying Cabinet and kept at a temperature of 180 °C for 2 h, removed from oven and cooled to room temperature. Open the autoclave, remove the camera and wipe the outside with a cotton swab moistened with alcohol. In parallel, this autoclave is carried out controlling experience.

4.2.3. Determination of boron

The resulting salt according to claim 4.2.1 or claim 4.2.2 dissolve 2.5 cmhydrofluoric acid (1:9), add 1 cm40% solution of formaldehyde and put on the electric stove for the complete removal of nitrogen oxides. The solution is quantitatively transferred into Teflon cylinder, pour in 1.5 cmof sulphuric acid (1:1), the volume adjusted to 10 cmof deionized water, poured into 0.4 cmsolution butylamine, 9 cmof toluene and 1 cmof acetone. Boron is extracted by shaking the solution in the cylinder within 2 min. after 10 min, separation of aqueous and organic phases are transferred to 8 cmof the organic phase of the piston pipette in a volumetric flask with a capacity of 25 cmand the volume was adjusted to the mark with acetone and mix thoroughly. The optical density measured on a spectrophotometer at 610 nm in relation to control experience; using cuvettes for photometry with the optical path length of 50 mm. Mass fraction of boron is determined according to the calibration schedule. In parallel spend control experience on the boron content in the reagents through all stages of the analysis.

4.2.4. Construction of calibration curve

In Teflon cylinders poured with microburette 0,0; 0,1; 0,2; 0,4; 0,6; 0,8; 1,0; 2,0 cmstandard solution boron (B), pour 2.5 cmhydrofluoric acid (1:9) 1.5 cmof sulphuric acid (1:1) volumes adjusted to 10 cmof deionized water, poured into 0.4 cmsolution butylamine, 9 cmof toluene and 1 cmof acetone. Next, carry out analysis as specified in paragraph 4.2.3.

Build a calibration graph of optical density on concentration, used to determine the boron content in the sample.

4.3. Processing of the results

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

,

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

 — the weight of the portion,

For the results analysis be the arithmetic mean of two parallel definitions, drawn from separate batches.

4.3.2. The difference between the larger and the smaller of the two results of parallel measurements with a confidence probability of 0.95 does not exceed the allowable absolute values of the differences of parallel measurements, are given in table.7.

Table 7

Permitted discrepancies for the intermediate mass fraction is calculated using linear interpolation.

4.3.3. To verify the correctness of the analysis using the method of additives. Two sample one of the samples analysed is dissolved according to claim 2.2.1 or claim 2.2.2. To the resulting solution add the same volume of working solution of boron so that the mass fraction of boron in the sample with the additive (a), calculated by the formula

,

where is the result of the analysis of the sample, %;

 — the mass of sample, g;

 — weight of boron in the added volume of the working solution of boron, µg, should be no more than the upper limit of the interval defined by the mass fraction of boron (see table.1) and at least tripled the value of the lower bound of this interval.

Analysis think is right with confidence probability of 0.95, if the result of analysis of the sample with the additive differs from by no more than

,

where  — the permissible discrepancy of the two results of parallel measurements of boron in the same sample without additives, %;

 — the permissible discrepancy of the two results of parallel measurements of boron in the same sample with the additive %.

Section 4. (Added, Rev. N 1).