GOST 13938.2-78

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  ГОСТ 13938.2-78

GOST 13938.2−78 Copper. Methods for the determination of sulfur (with Amendments No. 1, 2, 3, 4)

GOST 13938.2−78

Group B59

INTERSTATE STANDARD

COPPER

Methods of determining sulphur

Copper. Methods for determination of sulphur

AXTU 1709

Date of introduction 1979−01−01

INFORMATION DATA

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

DEVELOPERS

G. P. Giganov; E. M. Peneva; A. A. Blyahman; E. D. Shuvalov, A. N. Savelieva

2. APPROVED AND promulgated by the Decree of the State Committee of standards of Ministerial Council of the USSR from 24.01.78 N 155

3. REPLACE GOST 13938.2−68

4. The standard conforms to ISO 7266−84

5. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS

6. Limitation of actions taken by Protocol No. 3−93 Interstate Council for standardization, Metrology and certification (ICS 4−94)

7. REPRINT (November 1999) with Amendments No. 1, 2, 3, 4, approved in December 1979, April 1983, June 1985, April 1988 (IUS 2−80, 7 to 83, 8−85, 7−88)


This standard establishes titrimetric and photometric methods for the determination of sulfur in copper (at a mass fraction of sulfur from 0.001 to 0.02%).

(Changed edition, Rev. N 1, 4).

1. GENERAL REQUIREMENTS

General requirements for methods of analysis and safety requirements when performing tests according to GOST 13938.1.

Sec. 1. (Changed edition, Rev. N 4).

2. TITRIMETRIC METHOD

2.1. The essence of the method

The method is based on the combustion of a sample of copper containing sulphur in a current of 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.

2.2. Apparatus, reagents and solutions

Setup for the determination of sulfur (hell.1). You can use the installation of other construction providing the desired temperature of the furnace, the tightness of the system and cleaning of the feed oxygen, or automated analyzer of any type.

Damn.1

Damn.1

Before testing, check tightness of the device and correct assembling it. To do this, connect the entire device with a balloon containing oxygen, open the three-way stopcock to 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 in front of the absorption vessel. 2−3 min should stop the bubbling in the wash bottles, and then need to wait about 5−7 min. If the bubbles are no longer selected, the system can be considered sealed.

The installation consists of the following parts: oxygen cylinder 1 provided with a pressure reducing valve for regulating the rate of supply of oxygen in the furnace; a gas washing bottle 2, containing a solution of potassium permanganate in a solution of potassium hydroxide or sodium hydroxide; the flask 3, containing in the lower part of fused calcium chloride and a layer of glass or ordinary wool, and in the upper — potassium hydroxide or sodium hydroxide; crane 4, which gives the possibility to regulate the flow of purified oxygen tube for combustion, the furnace tube with 5 silicafume heaters that provide heating to 1250 °C; thermostat to regulate and maintain the desired temperature in a furnace with a thermocouple and a millivoltmeter or a potentiometer of any type; the absorption vessel 12, consisting of two identical vessels are connected by glass bridges. Allowed the use of two glass cylinders with a height of 250 mm from the glass the same color (Fig.2); burettes for titration 13.

Damn.2

Damn.2

Desiccator, according to GOST 25336 filled with calcium oxide according to GOST 8677, pre-calcined at a temperature 970−1050 °C, or calcium chloride.

Potassium dichromate according to GOST 4220, recrystallized twice and dried at 170 °C; 0,025 n. solution: 1,226 g of potassium dichromate was placed in a volumetric flask with a capacity of 1 DM, made up to the mark with water and mix.

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

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

Sodium hydroxide according to GOST 4328, a solution of 400 g/DM.

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

Calcium chloride, fused at the NTD.

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

The soluble starch according to GOST 10163, a solution of 10 g/DM.

The anhydrous sodium carbonate according to GOST 83.

Chernovetskiy sodium (sodium thiosulfate), of 0.025 n solution; prepare 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 well.

The installation of the mass concentration of the solution servational sodium

In a conical flask with a capacity of 250 cmpour 10 cmof sulphuric acid diluted 5:100, add 10 cmof a solution of potassium iodide, 25 cmof 0.025 n solution of potassium dichromate. Close the flask with ground stopper and leave in a dark place for 8−10 min. Add 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, add 2 cm ofstarch solution and continue titration until the disappearance of blue color.

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

,

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

The standard sample of copper, steel (non-alloy) or iron with a mass fraction of sulfur 0,002−0,03%.

Iodine GOST 4159, 0,001 n solution; prepared as follows: 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 titer of the iodine solution, expressed in grams of sulfur, set in four batches a standard sample with known sulfur content. Burning sulfur in this case is carried out as specified in clause 2.4.

The titer of a solution of iodine sulphur (is) in grams is calculated by the formula

,

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 standard sample mass concentration of iodine solution are placed on the solution servational sodium mass concentration which is installed in the solution of potassium dichromate.

The installation of the mass concentration of iodine solution

For installation of the mass concentration of iodine solution prepared 0,001 n solution of sodium servational with the dilution of 0.025 n solution: pipetted 10 cmof 0.025 n solution of sodium chernovetskogo, placed in a volumetric flask with a capacity of 250 cm, add pre-boiled and chilled water to the mark and mix. The solution is prepared the day of application. In a flask with a capacity of 250 cm18−20 cm pouredwater, poured from the burette accurately measured 20 cmof iodine solution, dilute with water to 70−80 cm, mixed and titrated with a solution of 0.001 n sodium chernovetskogo until then, until the color of solution becomes light yellow, then pour 2 cm ofstarch solution and continue titration until the disappearance of blue color.

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

*,

where is the mass concentration of sodium chernovetskogo equal *;

the volume of the solution servational sodium, spent on titration, sm.
_________________
* Formula and explication to it correspond to the original. — Note the CODE.

The titer of a solution of iodine sulphur (is) in grams is calculated by the formula

.

Allowed the use of other reagents, subject to obtaining the metrological characteristics are not inferior to those specified in the standard.

(Changed edition, Rev. N 2, 4).

2.3. Preparation for assay

Before analysis equipment for combustion test at 1200−1250 °C for leaks and for the presence of volatile reducing substances. To do this in both the absorption vessel apparatus pour 50 cmwater and 10 cmstarch solution, poured from the burette a few drops of iodine solution to the appearance of the blue color (intensity of color in both the vessels should be the same), the furnace is heated up to 1100−1200 °C and allow oxygen at a speed of 40−50 bubbles in 1 min.

If after 4−5 min, the color of the solution in the left vessel disappears, this means that stand out from the tube reducing agents that react with iodine. In this case, without interrupting the current of oxygen to the solution in the left vessel poured a few drops of iodine solution and continue the addition of iodine solution until a blue coloration in the solution will remain constant and the same intensity with the color of the solution in the right container.

(Changed edition, Rev. N 4).

2.4. Analysis

A sample of copper with a mass of 2.0 g (at a mass fraction of sulfur up to 0.005%) by weight or 1.0 g (for the mass concentration of sulfur in excess of 0.005%) distributed evenly along the bottom of the calcined boats for burning.

Then in a tube furnace (in the most heated zone) put a boat of linkage of copper with a long hook made of steel wire with a diameter of 2−3 mm. the furnace Tube immediately connect with the rest of the hardware and burn a sample of copper. The rate of transmission of oxygen must be maintained such that the liquid in the absorption vessel (see the devil.2, left part) were raised to an additional height of 2−3 cm When leaving the furnace in the absorption vessel gases begin to decolorize the iodine solution, pour the iodine solution at such a rate that the blue color did not disappear during burning of the sample. Burning sulphur is complete when the color of the solution in the absorption solution remains constant and the same intensity with the color of the solution in the right part of the vessel for absorption.

3. PHOTOMETRIC METHOD

3.1. The essence of the method

The method is based on the combustion of a sample of copper containing sulphur in a current of oxygen at 1200 °C, absorbing the resulting sulfur dioxide is a weak alkaline solution estradnogo pink and measuring the optical density of the solution at a wavelength of 530 nm.

3.2. Apparatus, reagents and solutions

Setup for the determination of sulfur as described in claim 2.2.

Spectrophotometer or photoelectrocolorimeter with all accessories.

Vessel to absorb sulphur dioxide (damn.3).

Damn.3

Damn.3

Astronomy pink FG.

Solutions estradnogo pink FG.

Solution A, prepared as follows: 0.4 g estradnogo pink and 5 g of sodium chloride was placed in a volumetric flask with a capacity of 1 DM, dissolved in water, add 20 cmto 0.001 n solution of formaldehyde, mix thoroughly and add water to the mark.

Solution stored in a vessel made of dark glass.

Shelf life not more than three months.

Solution B is prepared as follows: 5.0 cmmortar And placed in a volumetric flask with a capacity of 50 cm, add 5.0 cmof a solution of sodium bicarbonate and then filled to the mark with water.

The solution is used within 60 minutes after its preparation.

Sodium bicarbonate according to GOST 4201, a solution of 50 g/DM.

Sodium chloride according to GOST 4233.

Formalin technical GOST 1625.

Formaldehyde solution, freshly prepared 0,001 n.; prepared as follows: 5 cm informalin diluted with water to 500 cm. Pipetted 5 cmof this solution to a volumetric flask with a capacity of 1 DMand topped to the mark with water.

Standard samples of copper, steel (non-alloy) or iron with a mass fraction of sulfur 0,002−0,03% for building of calibration curve.

3.3. Preparation for assay

Before analysis equipment for combustion-check for leaks and the presence of volatile reducing substances as follows: in a vessel to absorb sulphur dioxide pour 50 cmthe exact solution B estradnogo pink and attach it to the equipment for combustion. The furnace is heated to 1200 °C and oxygen is passed at a speed of 40−50 bubbles per minute. After 10 minutes, disconnect the absorption vessel and measure the optical density of the solution (starting solution) at a wavelength of 530 nm in a cuvette with an optimum thickness of the layer. Solution comparison in the measurement of optical density is water.

This check is performed before each series of experiments as long as the difference between the largest and smallest values of the optical density of solutions will not exceed 0.01.

3.4. Analysis

3.4.1. A sample of copper (tab.1) calcined placed in a boat to burn. In a vessel to absorb sulphur dioxide pour 50 DMexact solution B estradnogo pink and attach it to the apparatus for burning sulfur.

Table 1

In a tube furnace (in the most heated zone) put a boat of linkage of copper with a long hook made of steel wire with a diameter of 2−3 mm, and burn a sample of copper at 1200 °C and the flow rate of oxygen 40−50 bubbles in 1 min.

At the end of combustion (approximately 10 s) during the next 10 minutes, continue the transmission of oxygen. The absorption vessel is detached and measure the optical density of the solution at a wavelength of 530 nm in a cuvette with an optimum thickness of the layer. Solution comparison in the measurement of optical density is water.

Optical density of the solution is measured no later than 30 minutes after absorption of sulfur dioxide. The obtained value of optical density is subtracted from the value of the optical density of the initial solution.

The mass of sulphur in the solution set for the calibration schedule.

3.4.2. Construction of calibration curve

Sample standard samples of copper, steel or iron containing from 5 to 70 mg of sulfur, placed in a boat for burning, and further analysis is carried out as described in section 3.4.1.

On the found values of differences of the optical densities of the initial solution and the optical densities of the solutions obtained by absorption of sulfur dioxide formed by the combustion of standard samples and their corresponding sulfur contents build the calibration graph.

4. PROCESSING OF THE RESULTS

4.1. Mass fraction of sulfur () in % for the titrimetric method described by the formula

,

where the titer of the iodine solution, expressed in grams of sulfur;

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

 — weight of copper,

4.2. Mass fraction of sulfur () in percent for the photometric method is calculated by the formula

,

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

 — weight of copper,

4.3. Discrepancies between the results of two parallel measurements and the two tests should not exceed the values given in table.2.

Table 2

(Changed edition, Rev. N 4).

4.4. The differences in the assessment of mass fraction of sulfur is used titrimetric method.

(Added, Rev. N 4).


APP. (Deleted, Rev. N 4).