GOST 6689.18-92

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  ГОСТ 6689.18-92

GOST 6689.18−92 Nickel, alloys Nickel and copper-Nickel. Methods of determining sulphur

GOST 6689.18−92

Group B59

STATE STANDARD OF THE USSR

NICKEL, ALLOYS NICKEL AND COPPER-NICKEL

Methods of determining sulphur

Nickel, nickel and copper-nickel alloys. Methods for the determination of sulphur

AXTU 1709

Date of introduction 1993−01−01

INFORMATION DATA

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

DEVELOPERS

V. N. Fedorov, Y. M. Leybov, Boris Krasnov, A. N. Bulanova, I. A. Vorobyev

2. APPROVED AND put INTO EFFECT by Decree of the Committee on standardization and Metrology of the USSR from 18.02.92 N 167

3. REPLACE GOST 6689.18−80

4. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

This standard specifies iodometric method (at a mass fraction of sulfur from 0.001 to 0.05%) and the method using automatic and semiautomatic analyzers (mass fraction of sulfur with from 0.001 to 0.05%) for the determination of sulfur in Nickel and copper-Nickel alloys according to GOST 492* and GOST 19241.
_________________
* On the territory of the Russian Federation GOST 492−2006. — Note the manufacturer’s database.

1. GENERAL REQUIREMENTS

General requirements for methods of analysis GOST 25086 with the addition of sec. 1 GOST 6689.1.

2. TITRIMETRIC METHOD FOR THE DETERMINATION OF SULFUR

2.1. The essence of the method

The method is based on the combustion of the sample in flowing oxygen at 1350−1400 °C, the absorption of evolved sulfur dioxide with water and titration of the resulting sulfurous acid solution of iodine.

2.2. Apparatus, reagents and solutions

Installation for determination of sulfur content (see drawing) consists of a oxygen cylinder 1; a pressure reducing valve 2; a gas washing bottle 3 with a solution containing 40 g/lpotassium permanganate and 40 g/DMhydroxide; a gas washing bottle 4 with a solution of 400 g/DMof potassium hydroxide; the column for drying of oxygen — 5, containing in the lower part of anhydrous calcium chloride, then a layer of glass or ordinary wool, and in the upper part of potassium hydroxide; the three-way tap 6, to direct the oxygen passed clean, into the oven or release it into the atmosphere and to further regulate the rate of oxygen transmission; a porcelain tube 7 the inner diameter of 18−22 mm, the ends of which, emerging from the furnace, must be of length at least 100 mm (tube before use, must be calcined in an oxygen atmosphere at 1200 °C); horizontal electric tubular furnace 8 with automatic temperature control up to 1400 °C; dust collector 9, filled with glass wool; two-way tap 10; two adsorption vessels 11 and 12; burettes 13 with a capacity of 10 or 25 cm.

Potassium hydroxide, a solution of 400 g/DM

Unglazed porcelain boats N 2 according to GOST 9147. Pumps pre-calcined at 1350−1400 °C in an oxygen atmosphere. The completeness of the burning of sulfur and its compounds from boats is controlled by passing the gaseous products from the furnace through a solution of iodine in presence of starch. The end of burning sulfur from boats is determined by the cessation of bleaching iodobromine solution.

Copper with a mass fraction of sulfur no more than 0.001% in the form of chips with thickness of 0.05−0.1 mm.

Standard sample for setting the operating mode of the installation. Using the State standard samples of steels: GEO 716−84п of the bonds 1557−83п of the bonds 1640−83п of the bonds 888−84п of the bonds 1416−82п or Nickel alloy, 1862−80 GSO, GSO 1862−85п of the bonds 1498−83п of the bonds 1609−85п.

Oxygen gas according to GOST 5583.

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

Potassium permanganate according to GOST 20490, a solution of 40 g/DM.

Wash solution: in a volumetric flask with a capacity of 1 DMcontribute 40 g of potassium permanganate, dissolved in 500−600 cmof water, add 400 g of potassium hydroxide, cool the solution and dilute to the mark with water.

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

Mercury iodide.

Calcium chloride according to GOST 450, fused, anhydrous.

The starch according to GOST 10163, a solution of 10 g/DMof 10 g of starch is mixed with a small amount of water until a homogeneous mass. The starch suspension is poured while stirring into 1 inchof hot water. The solution was boiled for 2−3 min and filtered through a folded filter into the flask, which is placed 0.03−0.05 g of iodide of mercury.

Potassium dichromate according to GOST 4220, 0,0125 mol/DMsolution: prepared from the drug, recrystallized twice and dried at 170 °C.

The anhydrous sodium carbonate according to GOST 83.

Sodium thiosulfate crystal according to GOST 244, solutions of 0.0125 mol/land 0.0005 mol/DM: a solution of 0.0125 mol/DMis prepared 2−3 days before the establishment of the mass concentration of a solution of 6.2 g chernovetskogo sodium dissolved in 100 cmsvejeprokipachenna chilled water, add 2 g of sodium carbonate and dilute with water to 1000 cm. A solution of 0.0005 mol/DMsodium thiosulfate prepare the appropriate dilution of 0.0125 mol/DMsolution svejeprokipachenna and chilled water.

The installation of the mass concentration of the sodium thiosulfate.

In a conical flask with cone with a capacity of 250 cmis placed 10 cmof hydrochloric acid, 10 cmpotassium iodide solution and 25 cmof 0.0125 mol/DMsolution of potassium dichromate. Close the flask with ground stopper and leave in a dark place for 8−10 minutes Rinse the walls of the bulb a small amount of water (total solution volume should be 70−80 cm) and titrated the liberated iodine with sodium thiosulfate to a light yellow color of the solution, add 2 cm ofstarch solution and continue titration until the disappearance of blue color.

The mass concentration of 0.0125 mol/DMsolution of sodium thiosulphate by potassium dichromate in grams is calculated by the formula

,

where is the volume of sodium thiosulfate consumed in the titration, sm.

Iodine crystal according to GOST 4159, a solution of 0.0005 mol/DM: of 1.27 g of crystalline iodine and 2.5 g of potassium iodide is weighed into a porcelain Cup, stirred with a small amount of water, triturated with a pestle and dissolve in water. The solution is transferred into a measuring flask with volume capacity of 1000 cmand topped to the mark with water. Solution store in a dark bottle with a glass stopper. 100 cmof the resulting solution placed in a measuring flask with volume capacity of 1000 cmand top up with water to the mark. The solution is prepared the day of application. Allowed the preparation of 0.0005 mol/DMsolution of iodine dilution of 0.005 mol/DMsolution of iodine, made of fiksanala.

1 g of a standard sample of Nickel or steel placed in a porcelain boat. Remove the tube from the bladder out of the tube and with wire hook set the boat in the most heated zone of the tube. Then do as stated in claim 2.4.

The mass concentration of iodine solution , expressed in grams of sulfur per 1 cmof a solution, calculated by the formula

,

where  — weight of standard sample, g;

 — certified sulfur content in the standard sample, %;

 — the volume of iodine solution consumed for titration, sm.

In the absence of standard sample mass concentration of iodine solution can be determined by the sodium thiosulfate, mass concentration of which is determined by solution of potassium dichromate.

The installation of the mass concentration of the solution of iodine by sodium thiosulfate.

In a flask with a capacity of 250 cm18−20 cm pouredwater, poured from a burette 20 cmof iodine solution, dilute with water to 70−80 cm, mixed, titrated to 0.0005 mol/DMsolution of sodium thiosulfate until a light yellow color of the solution, pour 2 cm ofstarch solution and continue titration until the disappearance of blue color.

The mass concentration of 0.0005 mol/DMsolution of iodine by sodium thiosulfate is calculated by the formula

,

where is the mass concentration of 0.0125 mol/DMsolution of sodium thiosulphate by potassium dichromate, g;

 — the volume of sodium thiosulfate consumed in the titration, sm.

Mass concentration of solution of iodine sulphur (is) is calculated according to the formula .

2.3. Preparation of the unit for analysis

Before analysis, check the tightness of the installation at 1350−1400 °C. the oxygen tank is connected to the device, open the three-way tap in the air, carefully open the cylinder valve, allow oxygen at a speed of 20−30 bubbles per minute, switch the three-way valve to the position at which oxygen enters the furnace, and close the valve. After 2−3 min it should stop bubbling in the wash bottles, and then wait another 5−7 minutes If bubbles no longer stand out, consider installing tight.

The correct operation of all devices is controlled according to the standard model, virginua the size of the analyzed sample.

Prior to analysis check the porcelain tube in the presence of volatile reducing agents. For this round vessel is placed 50 cmwater and 10 cmstarch solution, poured from the burette a few drops of iodine solution to the appearance of blue color, raise the oven temperature to 1350−1400 °C and pass a current of oxygen. If after 4−5 min, the blue color decreases, then to the solution add a few drops of iodine solution to equalize the color in both vessels.

2.4. Analysis

A portion of the alloy in the form of chips with a weight of 1 g for the mass concentration of sulfur less than 0.01% and 0.5 g for the mass concentration of sulfur is from 0.01 to 0.05% placed in a porcelain boat, pull the plug out of the tube from the oxygen tank and using a wire hook set up the boat with rigging, covered with 1 g of copper shavings or sawdust, in the most heated zone of the tube. The tube is quickly stoppered and allow oxygen at such a rate to prevent the formation of vacuum in the furnace.

When leaving the furnace the gases begin to discolour the iodine solution at the bottom of the absorption vessel, poured from the burette, the iodine solution with such speed that the blue absorption color of the solution disappeared during combustion.

With a small decrease in the intensity of color of the solution in the absorption vessel slows the flow of iodine solution and stop if the color of the solution remains constant and equal to the color of the solution in the test vessel. After that, allow oxygen through the plant 1 more min, and if the color of the absorption vessel does not change, the combustion is complete.

2.5. Processing of the results

2.5.1. Mass fraction of sulfur in percent is calculated by the formula

,

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

 — mass concentration of iodine solution, expressed in g/cmsulfur;

 — the weight of the portion of alloy,

2.5.2. Discrepancies in the results of three parallel measurements (rate of convergence) and the results of the two tests (index of reproducibility) shall not exceed the values of permissible differences given in the table.

2.5.3. Control of accuracy of analysis results is guaranteed by the establishing of operating mode according to the State standard samples of steels and Nickel alloys (p.2.2) in accordance with GOST 25086.

2.5.4. Titrimetric method is used when differences in the assessment of the quality of Nickel, Nickel and copper-Nickel alloys.

3. THE METHOD USING AUTOMATIC AND SEMIAUTOMATIC ANALYZERS

3.1. The essence of the method

The method is based on determination of sulfur by means of automatic and semi-automatic analyzer that ensures the burning of the sample the sample of the alloy in a current of oxygen at 1200−1600 °C, the absorption of the formed sulphur dioxide with a solution of oxidizer and the determination of sulfur depending on the type of analyzer, conductometric, coulometric, or amperometric methods to measure the molecular absorption bands of sulphur dioxide in the infrared region of the spectrum.

3.2. Equipment

Automatic or semi-automatic analyzer of the type as-7932.

Allowed to use other types of automated and semi-automated analyzers.

3.3. Analysis

Determination of the mass fraction of sulfur is carried out according to the methods prescribed for this type of analyzer using the calibration State standard samples, e.g. a kit, comprising GEO 716−84п of the bonds 164−84п of the bonds 888−84п of the bonds 1377−82п and GSO 1416−82п, or Nickel alloys (see p.2.2).

3.4. Discrepancies in the results of three parallel measurements (rate of convergence) and the results of the two tests (index of reproducibility) shall not exceed the values of permissible differences given in the table.

3.5. Control of accuracy of analysis results is guaranteed by the establishing of operating mode according to the State standard samples of steels and Nickel alloys in accordance with GOST 25086.