GB/T 4700.7-1998 Chemical analysis methods for silicon-calcium alloys - Infrared absorption method and combustion potassium iodate titration method for determination of sulfur content
Some standard content:
GB/T4700.7--1998
This standard is equivalent to JIS G1324:1989 "Chemical Analysis Methods for Silicon Calcium Alloys" in terms of technical content\7.3 Combustion potassium iodate titration method and 7.5 Infrared absorption method for sulfur content determination. This revision combines GB/T4700.7-1988 and GB/T4700.8--1988 into one standard, including: Method 1 Infrared absorption method for sulfur content determination and Method II Combustion potassium iodate titration method for sulfur content determination. Compared with the original standard, the technical content of infrared absorption method adds the provision of "cleaning dust in the instrument after each analysis"; the determination range of combustion potassium iodate titration method is changed from ".0.070%\ to "0.005%~0.070%", and the melting temperature of the sample is changed from 1400~1450℃\ to 1350～1400℃". From the date of implementation, this standard replaces GB/T4700.7--1988 "Silicon calcium alloy chemical analysis method infrared absorption method for determination of sulfur content" and GB/T4700.8-1988 "Silicon calcium alloy chemical analysis method combustion potassium iodate titration method for determination of sulfur content". This standard was proposed by the former Ministry of Metallurgical Industry of the People's Republic of China. This standard is under the jurisdiction of the former Ministry of Metallurgy Information Standards Research Institute. The drafting units of this standard are: Xinyu Iron and Steel Co., Ltd., Jilin Ferroalloy Plant, Hunan Ferroalloy Plant. The main drafters of this standard are: Fu Tao, Dong Mingxue, Huang Rongqing, Zhang Shuiju, Zhang Yulan, Huang Jing. This standard was first issued in 1988.
National Standard of the People's Republic of China
Methods for chemical analysis of calcium-siliconThe infrared absorption method and the combustion-potassiumiodate titration method for the determination of sulfur content1Scope
This standard specifies the determination of sulfur content by infrared absorption method and combustion-potassiumiodate titration method. This standard is applicable to the determination of sulfur content in calcium-silicon alloys. Determination range: 0.005%~0.070%. 2 Method I Determination of sulfur content by infrared absorption method
2.1 Summary of the method
GB/T 4700. 71998
Replaces GB/T4700.7--1988
GB/T 4700. 8-1988
The sample is heated and burned in the oxygen flow of a high-frequency induction furnace. The generated sulfur dioxide is carried by oxygen to the measuring chamber of the infrared analyzer. Sulfur dioxide absorbs infrared energy of a certain wavelength. Its absorption energy is proportional to the concentration of sulfur dioxide. The sulfur content can be measured according to the change in the energy received by the detector.
Reagents and materials
Magnesium perchlorate: anhydrous, granular.
Caustic soda asbestos: granular.
Glass wool.
Tungsten granules: sulfur content is less than 0.0002%, particle size 0.8~1.4mm. Tin particles: sulfur content less than 0.0003%, particle size 0.4~~0.8mm. Pure iron: purity greater than 99.8%, sulfur content less than 0.002%, particle size 0.8~1.68mm. Oxygen: purity greater than 99.95%, other levels of oxygen can also be used if a low and consistent blank can be obtained. Power gas source: nitrogen or compressed air, with impurities (water and oil) less than 0.5%. Quality crucible: outer diameter × height, 23mm × 23mm or 25mm × 25mm, and burned in a high-temperature heating furnace at 1200C for 4h or burned with oxygen until the blank value is the lowest. 2.2.10 Crucible tongs.
2.3 Instruments and equipment
2.3.1 Infrared absorption sulfur analyzer (sensitivity: 0.1×10-6), the device of which is shown in Figure 1: Approved by the State Administration of Quality and Technical Supervision on December 7, 1998 160
Implementation on July 1, 1999
GB/T 4700.7-1998
1—Oxygen cylinder; 2—Two-stage pressure regulator; 3—Gas washing bottle; 4, 9—Drying tube 5—Pressure regulator; 6—High-frequency induction furnace; 7—Combustion tube; 8—Dust collector; 10—Flow controller; 11—Sulfur dioxide infrared detector Figure 1 Device diagram of infrared absorption sulfur analyzer
2.3.1.1 Gas washing bottle (Figure Note 3): Contains caustic soda asbestos (2.2.2). 2.3.1.2 Drying tube (Figure 4, 9): Contains magnesium perchlorate (2.2.1). 2.3.2 Gas source
2.3.2.1 The carrier gas system includes an oxygen container, a two-stage pressure regulator, and a timing control part that ensures the provision of appropriate pressure and rated flow. 2.3.2.2 The power gas source system includes power gas (2.2.8), a two-stage pressure regulator, and a timing control part that ensures the provision of appropriate pressure and rated flow.
2.3.3 High-frequency induction furnace
Should meet the requirements of the melting temperature of the sample.
2.3.4 Control system
2.3.4.1 The microcomputer processing system includes a central processing unit, a memory, a keyboard input device, an information center display screen, an analysis result display screen, and an analysis result printer, etc.
2.3.4.2 Control functions include automatic loading and unloading of crucibles and lifting of furnaces, automatic cleaning, analysis condition selection and setting, monitoring of analysis process and alarm interruption, collection, calculation and correction of analysis data, etc. 2.3.5 Measurement system
It is mainly composed of an electronic balance (sensitivity not greater than 1.0mg) controlled by a microprocessor, an infrared analyzer and electronic measuring elements. 2.4. Sample
The sample should pass through a 0.125mm sieve. www.bzxz.net
2.5 Analysis steps
2.5.1 Sample quantity
Weigh 0.200~～~0.250g of sample.
2.5.2 Blank test
Carry out a blank test along with the sample.
2.5.3 Analysis preparation
Debug and check the instrument to make it in a normal and stable state, and select the best analysis conditions. 2.5.4 Calibration test
2.5.4.1 According to the sulfur content of the sample to be tested, select the corresponding range or channel, and select three standard samples of the same type (the carbon content of the sample to be tested should fall within the sulfur content range of the selected three standard samples) for calibration in sequence. The fluctuation of the measured results should be within the allowable error range. To confirm the linearity of the system, otherwise the linearity of the system should be adjusted. 2.5.4.2 Different ranges or channels should be measured and calibrated respectively. When the analysis conditions change, the blank should be re-measured and calibrated. 161
2.5.5 Determination
GB/T 4700.7—1998
2.5.5.1 According to the sulfur content range of the sample to be tested, select the best analysis conditions respectively. 2.5.5.2 Evenly place the weighed sample (2.5.1) in three crucibles (2.2.9) which are pre-filled with 0.5000g tin particles (2.2.5) as the bottom and 0.3000g pure iron (2.2.6) on top, and then evenly cover them with 0.4000g pure iron (2.2.6) and 1.500g tungsten particles (2.2.4) in turn, and start analysis until the analysis results are read.
The analysis results of the three samples should be within the allowable difference range, otherwise additional analysis should be performed, and the three similar results should be taken and the arithmetic mean value should be reported.
2.5.5.3 Clean the dust in the instrument after each analysis. 2.6 Allowable Difference
The difference in analysis results between laboratories should not be greater than the allowable difference specified in Table 1. Table 1 Allowable difference
0. 005 ~~ 0. 015
>0. 015~~0. 025
3 Method
Combustion potassium iodate titration method
3.1 Method summary
Allowable difference
>0. 025--0. 045
>0.045~0.070
Allowable difference
The sample is burned in an oxygen stream, and sulfur is completely oxidized to sulfur dioxide. After being absorbed by the acid starch solution, it is titrated with a potassium iodate standard solution. 3.2 Reagents and materials
The water used in this standard is distilled water that has been boiled to drive out all carbon dioxide and cooled. 3.2.1
Oxygen: purity greater than 99.5%.
High temperature combustion tube: inner diameter × length, 20mm × 600mm or 24mm × 600mm, porcelain boat: preheated in a high temperature furnace at 1200C for 4 hours. Cooled for use. High purity iron: sulfur content less than 0.0010%.
Vanadium pentoxide: powder, sulfur content less than 0.0010%. Silica gel, activated alumina or magnesium perchlorate. Soda lime or sodium hydroxide: granular.
Chromic acid saturated sulfuric acid: in sulfuric acid (p1.84g/mL) and add potassium dichromate or chromic anhydride to saturate it, and use the upper clear liquid. Starch solution: weigh 1.0g soluble starch in a 300mL beaker, add 5mL water, and adjust: add 50mL boiling water, stir continuously, boil on an electric stove for about 1min, remove and cool. Take another 1.5g potassium iodide and dissolve it in 10mL water towel, add this solution to the starch solution, dilute with water to 100mL, and mix. 3.2.10 Absorption solution or reference solution: transfer 60ml. hydrochloric acid (1.5+98.5). Add 2mL starch solution (3.2.9) and 2~3 drops of potassium iodate standard solution (3.2.11) to make the solution light blue. Prepare two bottles of this solution when using. One bottle is used as the absorption solution during determination; the other bottle is used as the reference solution for judging the titration end point.
3.2.11 Potassium iodate standard solution
3.2.11.1 Preparation: Weigh 0.2225g potassium iodate standard reagent, 1g potassium iodide and 0.10g sodium hydroxide and dissolve in water, dilute to 1000mL and mix well.
3.2.11.2 Calibration: Weigh 0.5000g of standard sample with similar composition to the sample and proceed according to 3.5.3. Blank test shall be carried out according to 3.5.2. Calculate the sulfur titration of potassium iodate standard solution according to formula (1): T =
(V. ---V) X 100
The sulfur titration of potassium iodate standard solution, g/mL; Where: T--
mi-amount of standard sample, g;
S-sulfur content of standard sample, %;
GB/T 4700.7--1998
VI.--The volume of potassium iodate standard solution consumed in titrating the standard sample, mL; V. ——-The volume of potassium iodate standard solution consumed in titrating the blank test, mL. 3.3 Instruments and devices
3.3.1 The sulfur titration device is shown in Figure 2.
1 oxygen cylinder; 2 oxygen pressure gauge; 3 flow meter; 4 buffer bottle; 5 washing bottle, containing chromic acid saturated sulfuric acid; 6 drying tower, containing soda lime or sodium hydroxide (granular); 7 washing bottle, containing sulfuric acid (p1.84g/mL); 8 drying tower. Silica gel and activated alumina; 9 two-way piston; 10 high temperature combustion furnace (about 300mm long): 11 automatic temperature controller (with electric thermocouple), control the furnace temperature at 1400 ~ 1450C: 12 high temperature combustion tube; 13 porcelain boat; 14 silica gel plug; 15 drying tube; 16 absorption bottle (without floating beads); 17 reference solution; 18 micro burette Figure 2 Schematic diagram of sulfur determination device
3.3.2 absorption bottle as shown in Figure 3.
3.4 test sample
The test sample should pass through a 0.125mm sieve.
3.5 Analysis steps
3.5.1 Sample quantity
Weigh 0.5000g sample.
3.5.2 Blank test
GB/T 4700.7—1998
Figure 3 Absorption bottle
Perform a blank test on the porcelain boat (3.2.3) pre-filled with 1g high-purity iron (3.2.4) and 0.25g vanadium pentoxide (3.2.5) according to 3.5.3, and take the average value after several measurements.
3.5.3 Measurement
3.5.3.1 Connect all parts of the sulfur determination device and check the airtightness, heat the high-temperature combustion tube (Figure 2 Note 12) to control the temperature inside the tube at 1350~1400C, and transfer 40mL of absorption liquid (3.2.10) into the absorption bottle (Figure 2 Note 16). 3.5.3.2 Transfer the sample (3.5.1) into a porcelain boat (3.2.3) pre-filled with 1g of high-purity iron (3.2.4), and then cover it with 0.25g of vanadium pentoxide (3.2.5). Push it into the high-temperature part of the high-temperature combustion tube (Figure 2 Note 12), plug it tightly with a silicone plug (Figure 2 Note 14) (pay special attention to sealing), and slowly introduce oxygen to prevent the absorption liquid from flowing back.
3.5.3.3 Pass oxygen at a flow rate of about 600mL/min to burn the sample, and introduce the generated sulfur dioxide into the absorption bottle (Figure 2 Note 16). Compare with the reference solution (3.2.10), titrate with potassium iodate standard solution (3.2.11) until the test solution and the reference solution have the same light blue color, and then intermittently pass oxygen for 3 minutes at an oxygen flow rate of 900-1000mL/min controlled by the two-way piston (Figure 2 Note 9). If the absorption solution fades, continue to titrate with potassium iodate standard solution (3.2.11) until the test solution and the reference solution have the same light blue color as the end point. 3.6 Calculation of analysis results
Calculate the sulfur percentage according to formula (2): S (%) = (V, -Vo)T
-the volume of potassium iodate standard solution consumed in titrating the sample.mL; where: V-
V. -—Volume of potassium iodate standard solution consumed in the titration blank test, mL; 164
GB/T4700.7-1998
T—Titer of potassium iodate standard solution against sulfur, /mL; -Sample volume·g.
3.7 Allowable difference
The difference in analysis results between laboratories should not be greater than the allowable difference specified in Table 2 Table 2 Allowable difference
0. 005 ~~0. 015
>0. 015 ~0. 025
Allowable difference
>0.025-~0.045
>0. 045~0. 070
Allowable difference1 Connect all parts of the sulfur determination device and check the airtightness. Heat the high-temperature combustion tube (Figure 2 Note 12) to control the temperature inside the tube at 1350-1400C. Transfer 40mL of absorption liquid (3.2.10) into the absorption bottle (Figure 2 Note 16). 3.5.3.2 Transfer the sample (3.5.1) into the porcelain boat (3.2.3) pre-filled with 1g of high-purity iron (3.2.4), and then cover it with 0.25g of vanadium pentoxide (3.2.5). Push it into the high-temperature part of the center of the high-temperature combustion tube (Figure 2 Note 12), plug it tightly with the silicone plug (Figure 2 Note 14) (pay special attention to the seal), and slowly pass oxygen to prevent the absorption liquid from flowing back.
3.5.3.3 Pass oxygen at a flow rate of about 600mL/min to burn the sample, and introduce the generated sulfur dioxide into the absorption bottle (Figure 2 Note 16). Compare with the reference solution (3.2.10), titrate with potassium iodate standard solution (3.2.11) until the test solution and the reference solution have the same light blue color, and then intermittently pass oxygen for 3 minutes at an oxygen flow rate of 900-1000mL/min controlled by the two-way piston (Figure 2 Note 9). If the absorption solution fades, continue to titrate with potassium iodate standard solution (3.2.11) until the test solution and the reference solution have the same light blue color as the end point. 3.6 Calculation of analysis results
Calculate the sulfur percentage according to formula (2): S (%) = (V, -Vo)T
-the volume of potassium iodate standard solution consumed in titrating the sample.mL; where: V-
V. -—Volume of potassium iodate standard solution consumed in the titration blank test, mL; 164
GB/T4700.7-1998
T—Titer of potassium iodate standard solution against sulfur, /mL; -Sample volume·g.
3.7 Allowable difference
The difference in analysis results between laboratories should not be greater than the allowable difference specified in Table 2 Table 2 Allowable difference
0. 005 ~~0. 015
>0. 015 ~0. 025
Allowable difference
>0.025-~0.045
>0. 045~0. 070
Allowable difference1 Connect all parts of the sulfur determination device and check the airtightness. Heat the high-temperature combustion tube (Figure 2 Note 12) to control the temperature inside the tube at 1350-1400C. Transfer 40mL of absorption liquid (3.2.10) into the absorption bottle (Figure 2 Note 16). 3.5.3.2 Transfer the sample (3.5.1) into the porcelain boat (3.2.3) pre-filled with 1g of high-purity iron (3.2.4), and then cover it with 0.25g of vanadium pentoxide (3.2.5). Push it into the high-temperature part of the center of the high-temperature combustion tube (Figure 2 Note 12), plug it tightly with the silicone plug (Figure 2 Note 14) (pay special attention to the seal), and slowly pass oxygen to prevent the absorption liquid from flowing back.
3.5.3.3 Pass oxygen at a flow rate of about 600mL/min to burn the sample, and introduce the generated sulfur dioxide into the absorption bottle (Figure 2 Note 16). Compare with the reference solution (3.2.10), titrate with potassium iodate standard solution (3.2.11) until the test solution and the reference solution have the same light blue color, and then intermittently pass oxygen for 3 minutes at an oxygen flow rate of 900-1000mL/min controlled by the two-way piston (Figure 2 Note 9). If the absorption solution fades, continue to titrate with potassium iodate standard solution (3.2.11) until the test solution and the reference solution have the same light blue color as the end point. 3.6 Calculation of analysis results
Calculate the sulfur percentage according to formula (2): S (%) = (V, -Vo)T
-the volume of potassium iodate standard solution consumed in titrating the sample.mL; where: V-
V. -—Volume of potassium iodate standard solution consumed in the titration blank test, mL; 164
GB/T4700.7-1998
T—Titer of potassium iodate standard solution against sulfur, /mL; -Sample volume·g.
3.7 Allowable difference
The difference in analysis results between laboratories should not be greater than the allowable difference specified in Table 2 Table 2 Allowable difference
0. 005 ~~0. 015
>0. 015 ~0. 025
Allowable difference
>0.025-~0.045
>0. 045~0. 070
Allowable difference
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