GOST 1293.16-93

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  ГОСТ 1293.16-93

GOST 1293.16−93 lead-antimony Alloys. Methods of determining sulphur

GOST 1293.16−93

Group B59

INTERSTATE STANDARD

LEAD-ANTIMONY ALLOYS

Methods of determining sulphur

Lead-antimony alloys. Methods for determination of sulphur

OKS 77.120*
AXTU 1725
_______________
* In the index «National standards» 2007 ACS 77.120.60. -

Note the manufacturer’s database.

Date of introduction 1997−01−01

Preface

1 DEVELOPED by Eastern research mining and metallurgical Institute of nonferrous metals (VNIItsvetmet)

INTRODUCED by Gosstandart of the Republic of Kazakhstan

2 ADOPTED by the Interstate Council for standardization, Metrology and certification on 15 April 1994 (Report No. 2 MGS)

The adoption voted:

3 Decree of the Russian Federation Committee on standardization, Metrology and certification dated June 19, 1996 N 388 inter-state standard GOST 1293.16−93 introduced directly as state standard of the Russian Federation from January 1, 1997

4 INTRODUCED FOR THE FIRST TIME

1 SCOPE

This standard applies to lead-antimony alloys of US, USM, Ssua according to GOST 1292 and US-1 on the other 48−6-98−86 used for the production of batteries, and sets polarographic method for the determination of sulfur in the range of a mass fraction of about 0.0006−0.01%, and iodine — in the range 0,001−0,01%.

2 NORMATIVE REFERENCES

The present standard features references to the following standards:

GOST 8.326−89 ICG. Metrological certification of measuring instruments*
_______________
* On the territory of the Russian Federation are PR 50.2.009−94**here and hereinafter.
** PR 50.2.009−94 abrogated on the basis of the order of the Ministry of industry and trade of 30.11.2009 N 1081. — Note the manufacturer’s database. — Note the manufacturer’s database.

GOST 12.1.005−88 SSBT. General hygiene requirements for working zone air

GOST 83−79 Sodium carbonate. Specifications

GOST 200−76 Sodium posterolaterally 1-water. Specifications

GOST 1292−81 lead-antimony Alloys. Specifications

GOST 1293.0−83 lead-antimony Alloys. General requirements for methods of chemical analysis

GOST 2053−77 Sodium sulfurous 9-aqueous. Specifications

GOST 2263−79. caustic Soda technical. Specifications

GOST 3118−77 hydrochloric Acid. Specifications

GOST 4159−79 Iodine. Specifications

GOST 4167−74 Copper dichloride 2-water. Specifications

GOST 4204−77 sulfuric Acid. Specifications

GOST 4220−75 Potassium dichromate. Specifications

GOST 4232−74 Potassium iodide. Specifications

GOST 4234−77 Potassium chloride. Specifications

GOST 4328−77 Sodium hydroxide. Specifications

GOST 4658−73 Mercury. Specifications

GOST 5456−79 of Hydroxylamine hydrochloride. Specifications

GOST 5583−78 Oxygen gas technical and medical. Specifications

GOST 6709−72 distilled Water. Specifications

GOST 9147−80 Glassware and equipment lab porcelain. Specifications

GOST 10157−79 Argon gaseous and liquid. Specifications

GOST 10163−76 Starch soluble. Specifications

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

GOST 10678−76 orthophosphoric Acid heat. Specifications

GOST 14261−77 hydrochloric Acid of high purity. Specifications

GOST 14919−83 Appliance. General specifications

GOST 20490−75 Potassium permanganate. Specifications

GOST 24363−80 Potassium hydroxide. Specifications

GOST 25086−87 non-ferrous metals and their alloys. General requirements for methods of analysis

GOST 25336−82 Glassware and equipment laboratory glass. The types, basic parameters and dimensions

GOST 27068−86 Chernovetskiy Sodium (sodium thiosulfate) 5-water. Specifications

GOST 29251−91 oils. Burette. Part 1. General requirements

THAT 6−09−4711−81 Calcium chloride fused. Specifications

THAT 6−09−5319−86 Pyrogallol grade A

THAT 48−6-98−86 Alloy lead-antimony, grade CSS-1 for starter battery. Specifications

3 GENERAL REQUIREMENTS

3.1 General requirements for methods of analysis GOST and GOST 25086 1293.0 with additions.

3.2 the analysis result should be the arithmetic mean of two parallel definitions, the difference between which does not exceed the permissible discrepancy at a confidence probability of 0.95, as specified in methods of analysis.

3.3 accuracy Control analysis carried out by the method of variation of batches, by a method of additives, by comparing the analysis results obtained by different standardized or standardized and certified methods for standard samples at least once a month, and when changing reagents, solutions, after a long break.

3.3.1 control of the accuracy of the analysis method of variation of batches is carried out by comparing the results of analyses of samples of according to regulated standard and a modified suspension. The results are considered accurate if the difference between them does not exceed 0,71where  — the permissible discrepancy of the two results of the analysis.

3.3.2 Control of accuracy of analysis by the method of additions is carried out only in the case of polarographic determination of sulfur by finding mass percentage in the sample after adding aliquotes part of a standard solution of sulfur to the sample prior to analysis.

The arithmetic mean of the results of parallel measurements taken for the mass percent of sulfur in the sample with the additive.

Discrepancies between the results of parallel measurements in the sample with the additive should not exceed the allowable.

The amount of additive is calculated as the difference between the contents of the determined component in a sample with the additive () and the result of the analysis sample ().

The analysis is considered accurate if the value found additives different from the entered values were no more than

,

where and  — the permissible discrepancy of the two results of the analysis for the sample and the sample with the additive, respectively.

3.3.3 Control accuracy comparison of analysis results obtained by different methods, is carried out by comparing the results of the analysis of the same samples obtained by two different standardized methods or standard methods and certified according to GOST 8.010 and with the error not exceeding the error-controlled methods of analysis.

The analysis considered accurate if the difference (in absolute value) between the results of the main and control methods does not exceed

,

where and  — the permissible differences in results of analyses of the main and control methods, respectively.

3.3.4 accuracy Control analysis of standard samples is carried out by analyzing the sample.

The arithmetic mean of the results of parallel measurements taken for reproduced mass fraction of sulfur in the standard sample.

Analysis of the samples is considered accurate if the results of the analysis of a standard sample for a sulfur content different from the certified characteristics are not more than 0.71, where  — the permissible discrepancy between the results of the analysis.

3.3.5 the Report analysis must contain:

— data necessary to characterize the samples;

— the results of the analysis;

— reference to this standard;

— a description of any abnormalities seen in the analysis;

— indication for conducting the analysis of any operations not specified in this standard.

3.4 it is allowed to use methods for the determination of sulfur content using automatic analyzers certified according to GOST 8.326, and use of other equipment, materials, utensils and reagents, subject to obtaining the metrological characteristics are not worse than specified in this standard.

4 SAFETY REQUIREMENTS

4.1 safety Requirements — according to GOST 1293.0 with additions.

4.2 Lead-antimony alloys containing lead, antimony, arsenic, fire — and explosion-proof, toxic in the molten state.

4.3 Lead, arsenic and their compounds belong to the harmful substances of the 1st class, the antimony — 2nd hazard class according to GOST 12.1.005.

4.4 Maximum permissible concentration in the air of working zone of production areas lead and its compounds maximum single 0.01 mg/m, time-weighted average — 0.005 mg/m; antimony 0.5 and 0.2 mg/m; arsenious anhydride (arsenic) is 0.04, and 0.01 mg/maccording to GOST 12.1.005.

4.5 Performing analyses with the use of mercury should be carried out in accordance with the sanitary rules of design, operation and maintenance of production and laboratory facilities designed for work with mercury, its compounds and devices with mercury filling, approved by the health authorities.

4.6 When using compressed gases in the process of analysis is required to observe the rules of arrangement and safe operation vessels working under pressure, approved by Gosgortechnadzor.

5 POLAROGRAPHIC METHOD FOR THE DETERMINATION OF SULFUR

5.1 the essence of the method

The method is based on the recovery of sulphur compounds to hydrogen sulphide, Stripping and absorption solution of alkali in the presence of hydrochloric acid hydroxylamine and Trilon B with subsequent determination of sulfide ions in the mode perimentally polarography with mercury dripping electrode.

5.2 the Instrument, reagents and solutions

Polarograph AC (PU-1, PU-2 or similar types).

Installation for recovery of the sulfur and Stripping of hydrogen sulfide (figure 1).

Figure 1 — Installation for recovery of the sulfur and Stripping of hydrogen sulfide

1−4 — bubblers for purification of argon; 5−10 — safety flask; 6 — the unit
with thermostat; 7 — reaction vessel with a reducing mixture; 8, 8' -refrigerators;
9 receiver for capture of hydrogen sulfide; 11 — bubbler with distilled water

Figure 1 — Installation for recovery of the sulfur and Stripping of hydrogen sulfide

The unit according to GOST 14919.

Argon according to GOST 10157.

Mercury brand RO according to GOST 4658.

Distilled water according to GOST 6709.

Bidistilled water obtained by further distillation of distilled water in a quartz apparatus. All solutions and reagents are prepared with bidistilled water.

Hydrochloric acid according to GOST 14261 and the solution 1, 2:1.

Sulfuric acid according to GOST 4204, a solution of (NSO)=0,05 mol/l(0,1 n), made of fiksanala.

Orthophosphoric acid according to GOST 10678.

Potassium iodide according to GOST 4232.

Potassium hydroxide according to GOST 24363.

Potassium chloride according to GOST 4234, recrystallized, saturated solution.

Copper chloride 2-water according to GOST 4167.

The caustic soda technical GOST 2263, solutions of 100 and 250 g/DM.

Sodium sulfide (sodium sulfide) according to GOST 2053, recrystallized.

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

Sodium posterolaterally (hipofosfit sodium) according to GOST 200.

Hydroxylamine hydrochloride according to GOST 5456, solution: to 34.7 g of hydroxylamine hydrochloride was diluted with bidistilled water up to 250 cm.

Pyrogallol brand And on the other 6−09−5319, a solution of 250 g/DMin the solution 250 g/DMsodium hydroxide.

The alkaline mixture is aged not less than two days: in a volumetric flask with a capacity of 1 DMflow 600 cmsvejeprokipachenna and chilled double-distilled water was added 112 g of potassium hydroxide, stirred until dissolved, the solution was cooled and portions added to it 100 g Trilon B with stirring, diluted with bidistilled water, stirred and close a glass stopper.

The polarographic background: 80cmalkaline mixture is placed in a conical flask with a glass stopper with a capacity of 250 cm, flow 20 cmof a solution of hydroxylamine hydrochloride, 150 cmdouble-distilled water and stirred.

The background can be used within 2 days.

The mixture recovery: in the reaction flask with a capacity of 1−1,5 DMgo 730 cmof hydrochloric acid (1,2:1,0), added 444 g of potassium iodide, 150 g phosphonoacetate sodium 250 mg chloride of copper and 20 cmof phosphoric acid, mix. The mixture was stored in a flask with a glass stopper in the dark place. 150 cmof the mixture necessary to perform a series of definitions, carefully drained from the sediment of salts, purified from sulphur by boiling in a reaction vessel (see figure 1) by blowing argon with a speed of 25 to 30 vials 10 C for 6−8 hours.

Standard solutions of sulphate sulphur:

solution a: 6,25 cmof sulfuric acid solution is placed in a volumetric flask with a capacity of 100 cm, made up to the mark svejeprokipachenna double-distilled water, and stirred.

1 cmof the solution contains 100 micrograms of sulfur;

solution B: 10 cmsolution And placed in a volumetric flask with a capacity of 100 cm, svejeprokipachenna bring to mark with bidistilled water and stirred.

1 cmof a solution containing 10 micrograms of sulfur;

solution: 10 cmof solution B is placed in a volumetric flask with a capacity of 100 cm, svejeprokipachenna bring to mark with bidistilled water and stirred.

1 cmof the solution contains 1 µg of sulfur.

Solutions B and C prepared on the day of application.

Standard solutions of sulfide sulfur:

solution G: 75 mg of the crystal of sodium sulfide was placed in a volumetric flask with a capacity of 100 cm, pour the polarographic background to the mark, mix to dissolve the salt.

1 cmsolution G contains 100 µg of sulfur;

solution D: 10 cmsolution G was placed in a volumetric flask with a capacity of 100 cm, made up to the mark polarographic background and stirred.

1 cmof a solution D containing 10 micrograms of sulfur.

Solutions D and e

prepared on the day of application.

5.3 Preparation for assay

5.3.1 Collecting unit for recovery of sulfur and Stripping of hydrogen sulfide in accordance with figure 1. In bubblers (1−3), pour 50−100 cmof the alkaline solution of pyrogallol, in (4) is sodium hydroxide, (P) — bidistillated water, (5) and (10) safety bubblers. The receiver (9) pour 10 cmof the background electrolyte. Fitting pressure gauge gas cylinder with argon is connected to the bubbler (1) rubber hose, pre-boiled in sodium hydroxide solution (100 g/DM) and washed with distilled water. The other connection is carried out using vinyl chloride hoses. Refrigerators (8; 8') connected to a water tap flexible rubber hoses.

5.3.2 leak Test setup

The reaction flask (7), reverse a refrigerator (8) and a receiver (9) washed with hydrochloric acid and svejeprokipachenna with bidistilled water. Gather the installation in accordance with 5.3.1. In a flask (7) pour 150 cmpre-purified restorative compound, and a receiver (9) — 10 cmpolarographic background. Through the installation of flow flow of argon at a rate of 15−20 bubbles in 10 s. On the tightness of the installation is judged by matching the speed of passage of bubbles of argon in barbarah (1) and (11). All sections of the unit should be lightly lubricated with phosphoric acid or grated spectral pure graphite.

If the sections are not tight, they proshlifovat fine powder abrasive.

5.3.3 the control experience

Convinced of the tightness of the installation, connect the refrigerator (8) to the water supply and include the stove, adjusting the heat so that the mixture in the reaction vessel began to boil 8−10 min after boiling the mixture of regenerative Stripping of hydrogen sulfide is continued for 30 min. Then the receiver (9) is detached from the installation, the contents poured into the cell and remove polarogram.

Mode polarographically for PU-1: amplitude 20 mV; scan rate — 5 mV/s; current range — 0.25 to25; the dripping period is 3 s; the delay time is 1.9 s; initial voltage is 0.60 V. the peak Potential of sulfide ion is approximately minus 0.8 V relative to the saturated calomel electrode.

It is necessary to recharge the anode compartment of a cell a fresh saturated solution of potassium chloride as a result of diffusion of sulfide ions in the anode compartment and the potential of the peak may gradually move in a positive direction.

The peak height of sulfur measured vertically, is drawn through the top of the peak to the intersection with a tangent to the left branch of the peak or connecting the bases of the branches peak.

In similar conditions hold polarographically solutions, obtained by reduction of 0.1−0.2 µg of sulfate sulfur and calculates the correction control of the experience by the formula

, (1)

where is the mass of sulfur in the standard solution comparison, mcg;

the peak height of sulfur in a control experiment, mm.

 — the height of the peak in sulfur solution comparison, mm.

The installation think is workable, if the amendment reference experiment does not exceed 0.1 micrograms.

If the value of the reference experience more, spend more restorative cleaning mixture directly in the reaction vessel (7) in flowing argon at reflux for 1−2 h. Then disconnect the receiver, it svejeprokipachenna washed with bidistilled water and pour a new portion of the polarographic background. Distilled hydrogen sulfide for 30 min record polarogram control experience.

For two parallel values of the control experience, the difference between the heights of waves sulfide ions should not exceed 10% relative, otherwise clean recovery of the mixture is continued until a consistent low value in the reference experiment.

The adjustment value control experience check every day before starting work and after each transition from the distillation of large quantities of sulphur for Stripping small, and also when replacing the tank with argon, solutions in barbarah.

5.3.4 Verification of the correct operation of the unit

Correctness of installation check a standard Stripping solution of sulphate sulphur. After the control experience of the recovery mixture was cooled, then to the receiver (9) pour 10 cmof the polarographic background, and a thin section of the fridge with the help of pipette into the reaction flask (7) enter 0.2 cmstandard solution (B) sulfate sulfur. The sulfide was removed within 40 min after switching on the tiles. Then the solution from the receiver is transferred into the cell and remove polarogram as specified in 5.3.3.

The height of the peak on polarogram correlate with the height of the peak solution of 2 µg of sulfide sulfur in 10 cmsolution (for that, select a micropipette 0.2 cmof solution (L) of sulfide sulfur, is diluted polarographic background in a narrow graduated cylinder to 10 cm). The difference of the heights of both peaks shall not exceed 10% Rel. If the difference is larger than, and the solution of sulphate sulphur gives lower peaks, it is necessary to wash out the refrigerator svejeprokipachenna double-distilled water and repeat the assay. Oxidation itestosterone acid from the inner surface of the tube opposite the refrigerator at a time when the installation is not working, is a common cause of underestimation of the results of determination of sulfur. If a solution of sulphate sulphur gives a much higher peaks, we tested the amendment reference experiment according to 5.3.3.

5.4. Analysis

A portion of the crushed sample weight 0,100 g made through a thin section of the refrigerator in the reaction vessel. The receiver is poured 10 cmof the polarographic background. Attach the refrigerator (8), turn on the hot plate (6), to displace the air from the system, checking the tightness of the installation, in accordance with 5.3.2. As the heat recovery of a mixture of watching the dissolution of the sample. The speed of the sparging reduced to 10 bubbles in 10 s at the beginning of the dissolution and bring it to 20−25 bubbles in 10 s at the end of the dissolution test. After complete dissolution of the sample Stripping of hydrogen sulfide lead from the boiling mixture for 30 min. Then shut off the unit, disconnect the receiver from the tube refrigerator (8) and a safety flask (10), the absorption solution enters the electrolyzer and polarographic sulfide ion according to 5.3.3.

Cool the reaction flask, the tube of the refrigerator and the receiver is washed twice with boiled double-distilled water is poured into the receiver 10 cm,background electrolyte and attach the receiver.

In the reaction vessel make 0,12,0 cmstandard solution (B) or © sulphate sulphur (depending on the sulfur content in the sample) and carry out the Stripping of hydrogen sulfide after boiling the mixture for 30 min with the subsequent registration of polarogram in conditions similar to the terms of polarographically sample.

One portion of the recovery mixture (150 cm), it is possible to consistently pursue the determination of sulfur in 2.5 g of lead-antimony alloy.

5.5 processing of the results

5.5.1 Mass fraction of sulphur () in percent is calculated by the formula

, (2)

where is the mass of sulfur in the solution comparison, the mcg;

the peak height of sulfur of the sample solution, mm;

the peak height of sulfur in the reference experiment, mm.

the peak height of sulfur solution comparison, mm;

 — the weight of the portion of the sample,

5.5.2 Absolute values of differences between the results of two parallel measurements (convergence) and the results of two tests (reproducibility) with confidence probability of 0.95 should not exceed the values of permissible differences shown in table 1.


Table 1 — Permissible divergence

Percentage

The allowable discrepancy for the intermediate mass fraction of sulfur is calculated using linear interpolation.

5.5.3 accuracy Control analysis — 3.3.1 (mass of the modified sample 0,200 g), 3.3.3 and in accordance with 3.3.2 after adding a measured pipette standard solution of sulphate sulphur to the sample prior to analysis.

The amount of additive (amount of a standard solution) is chosen so that the peak height of sulfur increased 1.3−2 times.

6 IODOMETRIC METHOD FOR THE DETERMINATION OF SULFUR

6.1 the essence of the method

The method is based on the combustion of a sample of lead-antimony alloy in flowing oxygen at 1200 °C, the absorption of the formed sulphur dioxide with water and the titration of sulphurous acid solution of iodine in presence of starch.

6.2 Apparatus, reagents and solutions

Installation for determination of sulfur content (figure 2).

Figure 2 — Setup for the determination of sulfur

1−2 — bubblers for oxygen cleaning; 3 — drying column; 4 — potentiometer; 5 — thermocouple;
6 — tube furnace; 7 — unglazed porcelain boat; 8 — unglazed porcelain tube;
9 — extractor; 10 — microburette; 11 — absorption apparatus

Figure 2 — Setup for the determination of sulfur

Oxygen GOST 5583.

Desiccator, according to GOST 25336.

Boats unglazed porcelain GOST 9147.

Microburette with a capacity of 5 cmaccording to GOST 29251.

The standard sample of copper, iron or steel (unalloyed) with a sulfur mass fraction of 0.002 to 0.2%.

Sulfuric acid according to GOST 4204, diluted 5:100.

Hydrochloric acid according to GOST 3118.

Potassium iodide according to GOST 4232, a solution of 50 g/DM.

Potassium hydroxide according to GOST 24363 or sodium hydroxide according to GOST 4328, a solution of 400 g/DM.

Potassium permanganate according to GOST 20490, a solution of 40 g/DMin the solution of the hydroxide of potassium or sodium.

Potassium dichromate according to GOST 4220, solution (ToSGOn)=0.025 mol/l(0,025 n.); prepare fiksanala or as follows: 1,226 g of recrystallized and dried at 170 °With potassium dichromate is placed in a volumetric flask with a capacity of 1 DM, made up to the mark with water and mix.

Calcium chloride fused on the other 6−09−4711.

The anhydrous sodium carbonate according to GOST 83.

The soluble starch according to GOST 10163, a solution of 0.5 g/l, acidified with hydrochloric acid (15 cm.of acid in 1 DMsolution).

Chernovetskiy sodium (sodium thiosulfate) according to GOST 2706*, the solutions (NaSO)=0,025 mol/l(0,025); and 0.001 mol/DM(0,001 n).
_______________
* Probably a mistake of the original. Should read GOST 27068. — Note the manufacturer’s database.

A solution of 0,025 mol/DMcook for 2−3 days before use in the following manner: 6.2 g chernovetskogo sodium dissolved in 100 cmsvejeprokipachenna and cooled water, add 0.2 g of anhydrous sodium carbonate, add water to 1 DMand mix thoroughly.

The concentration of the solution set as follows: in a conical flask with a capacity of 250 cmpour 10 cmof sulfuric acid solution, 10 cmpotassium iodide solution, measure with a pipette 25 cmof a solution of potassium dichromate and mix thoroughly. Close the flask with ground stopper and leave in a dark place for 8−10 mins Pour water to a volume of 70−80 cmand titrate the liberated iodine with a solution of sodium servational until then, until the color of solution becomes light yellow, pour 10 cm ofstarch solution and continue titration until the disappearance of the blue color.

The concentration of the solution () chernovetskogo sodium is calculated by the formula

, (3)

where  — volume of the solution servational sodium, spent on titration, sm.

The concentration of the solution set for the three aliquote parts of a solution of potassium dichromate.

A solution of 0.001 mol/DM, is prepared as follows: 10 cmof solution with a concentration of 0.025 mol/DM, measured by a pipette, placed in a volumetric flask with a capacity of 250 cm, made up svejeprokipachenna and chilled to the mark with water and mix. The solution is prepared the day of application.

The concentration of the solution () is calculated by the formula

. (4)

Iodine GOST 4159, solution (I)=0.001 mol/DM(0,001 n), prepared from fixanal or by: to 0.127 g of iodine dissolved in 50 cmof a solution of potassium iodide and dilute the solution with water up to 1 DM. The solution was stored in a flask made of dark glass.

The mass concentration of iodine solution (titer of iodine solution sulphur) set out on three batches of a standard sample with a certified sulfur content. The analysis is performed in 6.4.

The titer of a solution of iodine sulphur (is) in g/cmis calculated by the formula

, (5)

where  — mass fraction of sulfur in the standard sample, %;

 — the volume of iodine solution consumed for titration, cm;

 — weight of standard sample, g.

In the absence of the standard sample and the concentration of iodine solution sets in the following manner: into a flask with a capacity of 250 cmpour 50−60 cmof water and pour the measured pipette 25 cm0.001 mol/DMsolution of iodine, stirred and titrated 0,001 mol/DMsolution of sodium servational until then, until the color of solution is pale yellow, pour 10 cm ofstarch solution and continue titration until the disappearance of the blue color.

The titer of a solution of iodine sulphur (is), g/cm, is calculated by the formula

, (6)

where  — volume of the solution servational sodium consumed for titration, cm;

16,03 — mass equivalent of sulphur.

6.3 Preparation for analysis

6.3.1 Collect installation for the determination of sulfur according to figure 2.

In bubblers (1−2) pour 50−100 cmalkaline solution of potassium permanganate, (3) go to sleep at ¾ calcium chloride, and the top filled with a layer of wool; dust collector (8) fill with cotton also. All connections are performed by means of rubber hoses, glass tubes inserted in rubber stoppers.

Horizontal tube furnace (6) is equipped sheltowee terminals that provide heating to 1200 °C. the Furnace is equipped with platinum-rhodium thermocouple (5) and a galvanometer, an electronic potentiometer (4) of type PSC-2.

In the oven is inserted unglazed porcelain tube (7) inside diameter of 15−20 mm and of such length that its ends were out of the oven at 180−200 mm. Tube should be calcined at 1200 °C in flowing oxygen.

Unglazed porcelain boat length 70−130 mm, a width of 7−12 mm and a height of 5−10 mm also needs to be calcined at 1200 °C in an oxygen atmosphere and tested for the sulfur content in terms of analysis; they should be stored in a desiccator.

The absorption apparatus consists of two identical vessels with a diameter of 30−40 mm, height 250 mm, connected by glass bridges. Inside one of the vessels passes a dispersant in the form of a closed crater (or ball) with many small holes.

Before performing definitions in each vessel poured in 50 cmwater, 10 cmstarch solution and a few drops of iodine solution to the same blue color. One of the vessels serves to control during the titration in another absorption vessel.

6.3.2 installing Collected for the determination of sulfur test at 1200 °C for leaks. To do this, open the container and passed through the oxygen with a speed of 10−20 bubbles per minute, clamp disconnect a porcelain pipe from the absorption vessel and, if after 3−5 minutes the bubbles do not stand out, consider installing tight.

6.3.3 Installation check for the presence of volatile reducing agents. To do this, in both vessels, the absorption apparatus is poured on 50 cmwater, 10 cmstarch solution and a few drops of iodine solution to the same blue color. Installation sealed, the leak current of oxygen at a speed of 50−60 bubbles per minute while heating the furnace to 1200 °C. If the coating solution in the absorption vessel disappears, then poured dropwise a solution of iodine from microburette until then, while the blue color of the solution will not be the same intensity with the color of the solution in the right container.

6.4 analysis

A portion of the crushed sample with a mass of 1,000 g is distributed evenly along the bottom of the pre-calcined and cooled in a desiccator pumps for combustion.

The boat with the hitch with a long hook made of steel wire with a diameter of 2−3 mm is placed in the most heated zone of the porcelain tube. The system quickly seal, closing the tube with a stopper. Burning of lead in a current of oxygen supplied at such a rate that the level of absorption of the mixture in the left vessel of the absorption apparatus was raised to an additional height of 1.5−2 cm as a bleaching solution in the absorption vessel, the exhaust from the furnace gases flow from microburette solution of iodine with such speed that the blue color of the solution did not disappear. Burning sulphur is complete, if the color of the solution in the absorption vessel remains constant and the same intensity with the color of the solution in the right vessel by passing an oxygen for 1 min.

6.5 processing of the results

6.5.1 Mass fraction of sulphur (),%, is calculated by the formula

, (7)

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

the titer of a solution of iodine sulphur, g/cm;

 — the weight of the portion of the sample,

6.5.2 the Absolute values of the differences between the results of two parallel measurements ( — convergence) and the results of the two analyses (the reproducibility) with confidence probability of 0.95 does not exceed values of allowable differences specified in table 2.


Table 2 — Permissible divergence

Percentage

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

6.5.3 accuracy Control analysis — 3.3.1 (mass of the modified sample 0,500 g); 3.3.3; 3.3.4.

6.6. Presentation of results

6.6.1 presentation of results of analysis according to 3.3.5.