This standard specifies the determination of sulfur content by barium sulfate gravimetric method and combustion-potassium iodate titration method. This standard is applicable to the determination of sulfur content in limestone and dolomite, and also to the determination of sulfur content in metallurgical lime. The first part is the barium sulfate gravimetric method, the determination range: sulfur content greater than 0.10%; the second part is the combustion-potassium iodate titration method, the determination range: sulfur content 0.01% to 0.50%; Appendix A (the appendix of the standard) is the combustion-iodine titration method, the determination range: sulfur content greater than 0.010%. GB/T 3286.7-1998 Chemical analysis method for limestone and dolomite Determination of sulfur content GB/T3286.7-1998 Standard download decompression password: www.bzxz.net

GB/T 3286.7—1998
This standard amends GB/T3286.14—1984 "Chemical analysis method for limestone and dolomite - determination of sulfur content by sulfuric acid lock gravimetric method" and GB/T3286.15-1993 "Chemical analysis method for limestone and dolomite - determination of sulfur content by combustion-potassium iodate titration method". This revision merges the two original standards into one standard, which is described in two parts: the first part is the barium sulfate gravimetric method, and the second part is the combustion-potassium iodate titration method. The first part of this standard, the sulfuric acid gravimetric method, is not equivalent to the sulfur content determination method in JISM8850:1994 "Chemical analysis method for limestone". This revision of this standard clarifies in the "scope" that it is also applicable to the determination of sulfur content in metallurgical lime. The "allowable difference" adds the laboratory tolerance.
Appendix A of this standard is the appendix of the standard. GB/T3286 "Chemical analysis methods for limestone and dolomite" includes the following nine substandards: GB/T3286.1 Determination of calcium oxide content and magnesium oxide content; GB/T 3286.2
Determination of silicon dioxide content;
GB/T3286.3
GB/T 3286. 4
Determination of aluminum oxide content;
Determination of iron oxide content;
GB/T 3286.5
Determination of manganese oxide content;
GB/T3286.6 Determination of phosphorus content;
GB/T3286.7 Determination of sulfur content;
GB/T3286.8 Determination of loss on ignition;
GB/T 3286.9 Determination of carbon dioxide content. This standard replaces GB/T3286.14-1984 and GB/T3286.15-1993 from the date of implementation. 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 Information Standards Institute of the former Ministry of Metallurgical Industry. This standard was drafted by Wuhan Iron and Steel (Group) Corporation. The drafting units of this standard are: Wuhan Iron and Steel (Group) Corporation Technology Center, Beijing Research Institute of Mining and Metallurgy. The main drafters of this standard are: Cao Hongyan, Huang Yuehua, Zhao Pinzhen, Qian Jiasong, Gao Jieping, Cai Tianyun. This standard was first issued in February 1984, and GB/T3286.15-1993, which was issued in March 1993, replaced GB3286.15-1984, the method for determining sulfur content by methylene blue photometry. 70
1 Scope
National Standard of the People's Republic of China
Methods for chemical analysis oflimestone and dolomite
The determination of sulphur contentThis standard specifies the determination of sulphur content by the sulfuric acid lock gravimetric method and the combustion-potassium iodate titration method. GB/T 3286. 7 -- 1998
Replaces GB/T 3286.14—1984
GB/T 3286.15—1993
This standard applies to the determination of sulphur content in limestone and dolomite, and also to the determination of sulphur content in metallurgical lime. Part 1 Barium sulfate gravimetric method, determination range: sulfur content greater than 0.10%; Part 2 Combustion-potassium iodate titration method, determination range: sulfur content 0.01% to 0.50%; Appendix A (Appendix to the standard) Combustion-iodine titration method, determination range: sulfur content greater than 0.010%. 2 Reference standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard is published, the versions shown are valid. All standards will be revised, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T2007.2-1987 General rules for sampling and sample preparation of bulk mineral products Manual sample preparation method Part 1 Barium sulfate gravimetric method
3 Summary of the method
The sample is decomposed with nitric acid, potassium chlorate, and hydrochloric acid to convert sulfur into sulfate, and nitric acid is removed by fuming with perchloric acid. The test solution is filtered to remove silicon, and iron and aluminum ions are masked with ascorbic acid-EDTA. In the dilute hydrochloric acid solution, barium fluoride solution is added to make it into barium sulfate precipitation, which is filtered, burned, weighed, and the sulfur content is determined by the sodium sulfate weight method. 4 Reagents
4.1 Nitric acid (p1.42g/mL).
4.2 Hydrochloric acid (p 1. 19 g/mL).
4.3 Perfluoric acid (p1.67g/mL).
4.4 Hydrochloric acid (1+1).
4.5 Ammonia water (1+1).
4.6 Saturated potassium chlorate solution.
4.7 Ascorbic acid solution (20g/L), prepare when needed. 4.8 Disodium ethylenediaminetetraacetic acid (EDTA) solution Lc (EDTA) - 0.05mol/LJ: Weigh 3.72g EDTA in a 200mL beaker, add about 100mL water, add nitrogen water (4.5) dropwise under heating until the reagent is dissolved, cool, filter and dilute to 200mL with water State Administration of Quality and Technical Supervision Approved on December 7, 1998 Implementation on July 1, 1999
GB/T 3286.7 -1998
4.9 Barium chloride solution (100g/L): Take 50g barium chloride (BaClz·2Hz0) and dissolve it in appropriate amount of water, filter and dilute to 500mL with water. 4.10 Methyl orange solution (1g/L).
4.11 Silver nitrate solution (10g/L).
5 Instruments
In the analysis, only common laboratory instruments and equipment are used. 6 Sample preparation
Prepare the sample according to GB/T2007.2.
6.1 The sample should be processed to a particle size of less than 0.125mm. 6.2 Before analysis, the limestone and dolomite samples should be dried at 105-110℃ for 2h and placed in a desiccator to cool to room temperature. 6.3 The preparation of metallurgical lime samples should be carried out quickly. After preparation, the samples should be immediately placed in a ground-mouth bottle or plastic bag and sealed, and stored in a desiccator. The samples should not be dried before analysis.
7 Analysis steps
7.1 Sample quantity
Weigh 2.00g of sample, accurate to 0.001g. For metallurgical lime samples, the sample should be weighed quickly. 7.2 Blank test
Perform a blank test along with the sample.
7.3 Determination
7.3.1 Place the sample (7.1) in a 250mL beaker, moisten it with a small amount of water, and cover it with a watch glass. Slowly add 20mL nitric acid (4.1). After the violent reaction stops, add 10mL saturated potassium chlorate solution (4.6) and 4mL hydrochloric acid (4.2). Heat to decompose. Continue heating at low temperature to evaporate the test solution until it is nearly dry. Remove it and cool it.
Note: During the determination, the working environment should avoid sulfur trioxide smoke. 7.3.2 Rinse the watch glass and the wall of the cup with a small amount of water, add 4mL hydrochloric acid (4.2) and 8mL perfluoric acid (4.3), continue heating at low temperature until perchloric acid smoke is emitted, remove it and cool it.
7.3.3 Rinse the watch glass and the wall of the cup with water, add 5mL hydrochloric acid (4.2), dilute it to 50mL with water, heat it to boiling, and dissolve the salts. Filter the test solution into a 400mL beaker with medium-speed quantitative filter paper while it is still hot, wash the beaker with hot water, and wash the precipitate 5 to 6 times. 7.3.4 Dilute the filtrate with water to about 200mL, add 10mL ascorbic acid solution (4.7), let stand for 3 to 5 minutes, add 10mL of ETA solution (4.8), add two drops of methyl orange solution (4.10), neutralize with ammonia water (4.5) until the solution turns yellow, then add hydrochloric acid (4.4) until the solution changes from yellow to red, and add 4.0mL in excess, dilute with water to about 250mL, 7.3.5 Heat the test solution to boiling, add 15mL of barium chloride solution (4.9) under constant stirring, keep warm at 80~95℃ for 2h, remove, and let stand overnight at room temperature.
7.3.6 Filter with two slow quantitative filter papers, transfer the precipitate to the filter paper with hot water, and wash the precipitate and filter paper with a small amount of water each time until the filtrate is free of fluoride ions (check with silver nitrate solution (4.11)). 7.3.7 Place the filter paper and the precipitate in a constant weight platinum crucible, dry and ash carefully, and burn the platinum crucible in a high temperature furnace at 800-850℃ for 30 minutes. Take out the platinum, cool it slightly, place it in a desiccator to cool to room temperature, weigh it, and repeatedly burn it to a constant weight. 8 Expression of analysis results
Calculate the mass percentage of sulfur according to formula (1): [(mi - m) - (ms = m)] × 0.137 4 × 100S(%) =
Wherein: mi
-mass of barium sulfate precipitate and platinum crucible, g; m
mass of platinum crucible, g;
GB/T 3286.7 1998
-mass of blank test and platinum crucible, g;
mass of platinum used in blank test, g;
m—sample amount,g;
9 Allowable difference
-Conversion factor of barium sulfate to sulfur.
The difference between two independent analysis results in a laboratory and the difference between the analysis results of two laboratories should not be greater than the corresponding allowable difference listed in Table 1. For metallurgical lime samples, no allowable difference between laboratories is required. Table 1
0.10～0.25
>0. 25~~0. 50
10 Method Summary
Part II
Allowable difference within the laboratory
Combustion-potassium iodate titration method
Allowable difference between laboratories
The sample is mixed with tungsten trioxide and heated and burned at 1275℃±25℃ in a nitrogen flow to convert all sulfur in the sample into sulfur dioxide, which is absorbed by acidic potassium iodide-starch solution and titrated with potassium iodate standard solution. 11 Reagents
11.1 Nitrogen: purity greater than 99.5%.
11.2 Flux: tungsten trioxide (sulfur content less than 0.001%), powder. 11.3 Hydrochloric acid (1.5+98.5).
11.4 Potassium iodide-starch solution: weigh 2.0g soluble starch in a 300mL beaker, add 5mL water, and mix well. Add 50mL boiling water, stir constantly, heat and boil for about 1min, and cool. Take another 3.0g potassium iodide and dissolve it in 10mL water, add this solution to the starch solution, dilute with water to 100ml, and mix. Prepare when needed. 11.5 Potassium iodate standard solution
11.5.1 Potassium iodate standard solution [c (1/6K103) 0.003121mol/L]: Weigh 0.1113g of potassium iodate (not less than 99.9%) that has been dried at 105110℃ for 2h and cooled to room temperature, dissolve in water, transfer to a 1000mL volumetric flask, dilute to scale with water, and mix. 11.5.2 Potassium iodate standard solution [c (1/6KI0,) = 0.001560mcl/L]: Weigh 0.1113g of potassium iodate (not less than 99.9%) that has been dried at 105~～110℃ for 2h and cooled to room temperature, dissolve in water, transfer to a 2000mL volumetric flask, dilute to scale with water, and mix. 12 Instruments and devices
GB/T3286.7-1998
1314[15
1 Oxygen cylinder; 2 Nitrogen pressure gauge; 3 --Flowmeter;4-buffer bottle;5-washing bottle, filled with chromic acid saturated sulfuric acid;6-drying tower, filled with soda lime;7-washing bottle, filled with sulfuric acid (g1.84g/mL);8drying tower, filled with anhydrous calcium fluoride;9-porcelain boat 10-tube furnace;11-automatic temperature controller (thermocouple);12-porcelain tube, 13-two-way piston;14-air guide tube;15-absorption cup;16-full fixed tubeFigure 1 Schematic diagram of sulfur content determination device
$35±1
Frosting or sugar water
The float in the liquid
can automatically lift up
Figure 2 Absorption cup
The sulfur content determination device is shown in Figure 1.
12.1 Tubular high temperature furnace (horizontal): rated temperature 1400℃, equipped with thermocouple pyrometer and temperature automatic controller. 12.2 High aluminum porcelain tube
12.3 Porcelain boat: 88mm or 97mm long. Before use, burn in a high-temperature furnace at 1000℃ for more than 2h, cool slightly and place in an unoiled desiccator for standby use. When used for low sulfur determination, burn the porcelain boat at 1250℃ with nitrogen for 10min, cool slightly and place in an unoiled desiccator for standby use. 12.4 Absorption cup (see Figure 2), with a waste liquid discharge piston at the lower end. 74
13 Sample preparation
Prepare the sample according to GB/T2007.2.
GB/T 3286.7—1998
13. The sample should be processed to a particle size of less than 0.125mm. 13.2 Before analysis, the limestone and dolomite samples should be dried at 105-110℃ for 2h and placed in a desiccator to cool to room temperature. 13.3 The preparation of metallurgical lime samples should be carried out quickly. After preparation, the samples should be immediately placed in ground-mouth bottles or plastic bags and sealed, and stored in a desiccator. The samples should not be dried before analysis.
14 Analysis steps
14.1 Sample quantity
Weigh the sample according to Table 2, accurate to 0.0001g. For metallurgical lime samples, the sample should be weighed quickly. Table 2
Sulfur content, %
0.01~0.10
>0. 10~0. 20
>0. 20~0. 50
14.2 Blank test
Carry out a blank test along with the sample.
14.3 Determination
Sample amount.8bzxz.net
Flux amount,
Potassium iodate standard solution, mol/L
0.003 121
14.3.1 Connect the device according to Figure 1 and gradually raise the furnace temperature to 1275℃±25℃. Pass nitrogen to adjust the device to make it airtight and leak-proof. Analyze two samples with higher sulfur content according to 14.3.2~14.3.4, and do not calculate the analysis results. 14.3.2 Take 80mL of hydrochloric acid (11.3) in the absorption cup, add 4mL of potassium iodide-starch solution (11.4), adjust the ammonia flow rate to 200mL/min, and titrate with potassium iodate standard solution (11.5.1 or 11.5.2) until the absorption liquid turns light blue. 14.3.3 Place the sample in a porcelain crucible pre-filled with flux (11.2, see Table 2 for the amount), stir with a glass rod, carefully transfer and spread it in a porcelain boat (12.3). Open the stopper of the porcelain tube (12.2), push the porcelain boat into the high temperature of the porcelain tube with a stainless steel long hook, and immediately plug the tube. Adjust the nitrogen flow rate to 200mL/min, introduce the mixed gas after heating and combustion into the absorption cup, and immediately titrate with potassium iodate standard solution (see Table 2) to keep the absorption liquid blue during the titration process. When the color of the absorption liquid fades slowly, reduce the titration speed accordingly and increase the nitrogen flow rate appropriately. Titrate with nitrogen intermittently, titrate each time until the color of the starch absorption liquid is the same as the original adjusted end point color, until the color of the absorption liquid does not change to the end point, and turn off the nitrogen.
14.3.4 Open the stopper of the porcelain tube, and pull out the porcelain boat with a stainless steel long hook. 15 Summary of analysis results
Calculate the mass percentage of sulfur according to formula (2):
S (%) = VV)c × 0. 016 03 × 100m
Wherein, V
-the volume of potassium iodate standard solution consumed by the titration sample, mL, V. —the volume of potassium iodate standard solution consumed by the titration blank test, mL; -the concentration of potassium iodate standard solution, mol/Lm--the amount of sample, g;
0.01603——the mass of sulfur in grams equivalent to 1.00mL potassium iodate standard solution [c (1/6KI0.) = 1.00mol/L]. 75
16 Allowable difference
GB/T3286.7—1998
The difference between two independent analysis results in a laboratory and the difference between the analysis results of two laboratories should not be greater than the corresponding allowable difference listed in Table 3. For metallurgical lime samples, no allowable difference requirement between laboratories is required. Table 3
0. 010~0. 050
>0.050~0.100
>0.100~0.250
Permissible difference within the laboratory
Permissible difference between laboratories
A1 Range
GB/T 3286.7—1998
Appendix A
(Appendix to the standard)
Determination of sulfur content in limestone and metallurgical lime by combustion-iodine titration This method is applicable to the determination of sulfur content in limestone and metallurgical lime. The determination range: sulfur content greater than 0.010%. A2 Method Summary
Use iron powder and vanadium pentoxide as fluxes, and burn the sample in a high-temperature tube furnace with oxygen. The generated sulfur dioxide is absorbed by starch solution and titrated with iodine standard solution.
A3 Reagents
A3.1 Mixed flux: Take one part of reduced iron powder and one part of vanadium pentoxide that has been pre-burned at 550-600℃ for 2h and cooled to room temperature and mix them evenly.
A3.2 Starch absorption solution: Take 2g of soluble starch, mix it into a paste with a small amount of water, add 100mL of boiling water, stir and heat to boil, and cool. Add a few drops of hydrochloric acid (p1.19g/ml.), dilute to 1L with water, stir evenly and let it stand to clarify. Take 400ml of clarified liquid, dilute to 2L with water, and mix.
A3.3 Iodine standard solution:
A3.3.1 Weigh 3.81g of iodine, dissolve it in 100mL of potassium iodide solution (150g/L), transfer it to a 1000mL volumetric flask, dilute to the mark with water, and mix evenly. Store in a brown bottle and leave overnight. A3.3.2 Take 100 mL of iodine standard solution (A3.3.1) Add 4g potassium iodide to a 1000mL volumetric flask, dissolve, dilute to scale with water, and mix. The concentration of this iodine standard solution is c(1/2I2) = 0.003mol/L. A3.3.3 Calibration: Take three portions of limestone standard material and operate according to A6. The range of the number of milliliters of iodine standard solution consumed in the determination of three portions of standard material does not exceed 0.20mL, and the average value is taken. Calculate the titer of the iodine standard solution (A3.3.2) according to formula (A1): S m X_1 000
(V= V.) x 100
Where: T—titer of iodine standard solution for sulfur, mg/mL; S·mX10
V—average value of the volume of iodine standard solution consumed by titrating the standard material, mL; V. Average value of the volume of iodine standard solution consumed in the blank test, ml; S—sulfur content of the standard material, %;
-sample amount of the standard material, g.
Note: Lead sulfate (pre-burned at 800℃ for 1h and stored in a desiccator) or potassium sulfate (pre-dried at 105-110℃ for 2h and stored in a desiccator) can also be used to calibrate the iodine standard solution. Weigh 10 mg of lead sulfate or about 6 mg of potassium sulfate (accurate to 0.01mg) in triplicate on an analytical balance with a sensitivity of 0.01 mg, and operate according to A6.3.2~A6.3.4. A4 Instruments and Devices
A4.1 The sulfur content determination device is the same as Figure 1, but the carrier gas is oxygen and the gas source is an oxygen cylinder. A4.2 Tubular high-temperature furnace (horizontal): rated temperature 1400℃, equipped with a thermocouple pyrometer and temperature automatic controller. A4.3 High-aluminum porcelain tube.
A4.4 Porcelain boat: 88mm or 97mm in length, burn in a high-temperature furnace at 1000℃ for more than 2h before use, and place in an unoiled desiccator after cooling slightly for standby use.
A4.5 Absorption cup (same as Figure 2), with a waste liquid discharge piston at the lower end. 77
A5 Sample preparation
Prepare the sample according to GB/T2007.2.
GB/T 3286.7-
A5.1 The sample should be processed to a particle size of less than 0.125mm. 1998
A5.2 Before analysis, the limestone sample should be dried at 105~110℃ for 2h, and placed in a desiccator to cool to room temperature. A5.3 The preparation of metallurgical lime samples should be carried out quickly. After preparation, the sample should be immediately placed in a ground-mouth bottle or plastic bag and sealed, and stored in a desiccator. The sample should not be dried before analysis.
A6 Analysis steps
A6.1 Sample quantity
Weigh the sample according to Table A1, accurate to 0.0001g. For metallurgical lime samples, the sample should be weighed quickly. Table Al
Sulfur content, %
0.01~0.20
≥>0. 20～ 0. 50
A6.2 Blank test
Carry out a blank test with the sample.
A6.3 Determination
Sample quantity g
A6.3.1 Connect the sulfur determination device according to Figure 1, gradually increase the furnace temperature to 1325℃±25℃, pass oxygen and check the adjustment device to make it tight and leak-proof. Analyze the two samples with higher sulfur content according to A6.3.2~A6.3.4, and do not calculate the analysis results. A6.3.2 Add 50~60mL starch absorption solution (A3.2) to the absorption cup (A4.5), oxygenate, adjust the oxygen flow rate to 1.52.0L/min, titrate with iodine standard solution (A3.3.2) until the starch absorption solution turns light blue, use this as the titration end point color, and turn off the oxygen. A6.3.3 Spread the sample (A6.1) flat on the porcelain boat (A4.4), evenly covering it with 0.5g mixed flux (A3.1). Open the porcelain tube stopper, use a stainless steel long hook to push the porcelain boat (A4.4) into the high temperature of the porcelain tube (A4.3), immediately plug the porcelain tube stopper, and preheat for 1 minute. After preheating for 10~15 seconds, carefully open the piston in front of the absorption cup to discharge the carbon dioxide decomposed by the sample, and pre-place about 0.5mL iodine standard solution (A3.3.2) in the absorption cup. Carefully open the oxygen piston, adjust the oxygen flow rate, introduce the heated and burned mixed gas into the absorption cup, and immediately titrate with the iodine standard solution (A3.3.2) to keep the starch absorption liquid blue during the titration process. When the color of the absorption liquid fades slowly, reduce the titration speed accordingly and adjust the oxygen flow rate to 1.5~2.0 L/min. Titrate with oxygen intermittently, titrate each time until the color of the starch absorption liquid is the same as the original adjusted end point color, until the color of the absorption liquid does not change to the end point, and turn off the oxygen. Note: When using lead sulfate (or potassium sulfate) to calibrate the titration degree, preheating is not required. Since the sulfur dioxide release rate is fast and concentrated, the oxygen flow should be adjusted at a lower speed. For samples with a relatively high sulfur content, the oxygen flow should also be adjusted at a lower speed at the beginning of the titration. A6.3.4 Open the porcelain tube plug and pull out the porcelain boat (A4.4) with a stainless steel long hook. A7 Expression of analysis results
Calculate the mass percentage of sulfur according to formula (A2): T(V - V.)
S(%) =
m X 1 000
Wherein: T - the titration degree of sulfur by the iodine standard solution, mg/mL; V - the volume of the iodine standard solution consumed by the titration sample, mL; V. - the volume of the iodine standard solution consumed by the blank test, mL; - the amount of sample, g.3) At high temperature, immediately plug the porcelain tube stopper and preheat for 1 minute. After preheating for 10~15 seconds, carefully open the piston in front of the absorption cup to discharge the carbon dioxide decomposed by the sample, and pre-place about 0.5mL of iodine standard solution (A3.3.2) in the absorption cup. Carefully open the oxygen piston, adjust the oxygen flow rate, and introduce the mixed gas after heating and combustion into the absorption cup. Immediately titrate with iodine standard solution (A3.3.2) to keep the starch absorption liquid blue during the titration process. When the color of the absorption liquid fades slowly, reduce the titration speed accordingly and adjust the oxygen flow rate to 1.5~2.0 L/min. Titrate with oxygen in between, titrate each time until the color of the starch absorption liquid is the same as the original adjusted end point color, until the color of the absorption liquid does not change to the end point, and turn off the oxygen. Note: When using lead sulfate (or potassium sulfate) to calibrate the titer, preheating is not required. Since the sulfur dioxide release rate is fast and concentrated, the oxygen flow should be adjusted at a lower speed. For samples with a relatively high sulfur content, the oxygen flow should also be adjusted to a lower speed at the beginning of the titration. A6.3.4 Open the porcelain tube plug and pull out the porcelain boat (A4.4) with a stainless steel long hook. A7 Expression of analysis results
Calculate the mass percentage of sulfur according to formula (A2): T(V - V.)
S(%) =
m X 1 000
Where: T--titration degree of sulfur of iodine standard solution, mg/mL; V--volume of iodine standard solution consumed by titration sample, mL; V. --volume of iodine standard solution consumed by blank test, mL; -sample amount, g.3) At high temperature, immediately plug the porcelain tube stopper and preheat for 1 minute. After preheating for 10~15 seconds, carefully open the piston in front of the absorption cup to discharge the carbon dioxide decomposed by the sample, and pre-place about 0.5mL of iodine standard solution (A3.3.2) in the absorption cup. Carefully open the oxygen piston, adjust the oxygen flow rate, and introduce the mixed gas after heating and combustion into the absorption cup. Immediately titrate with iodine standard solution (A3.3.2) to keep the starch absorption liquid blue during the titration process. When the color of the absorption liquid fades slowly, reduce the titration speed accordingly and adjust the oxygen flow rate to 1.5~2.0 L/min. Titrate with oxygen in between, titrate each time until the color of the starch absorption liquid is the same as the original adjusted end point color, until the color of the absorption liquid does not change to the end point, and turn off the oxygen. Note: When using lead sulfate (or potassium sulfate) to calibrate the titer, preheating is not required. Since the sulfur dioxide release rate is fast and concentrated, the oxygen flow should be adjusted at a lower speed. For samples with a relatively high sulfur content, the oxygen flow should also be adjusted to a lower speed at the beginning of the titration. A6.3.4 Open the porcelain tube plug and pull out the porcelain boat (A4.4) with a stainless steel long hook. A7 Expression of analysis results
Calculate the mass percentage of sulfur according to formula (A2): T(V - V.)
S(%) =
m X 1 000
Where: T--titration degree of sulfur of iodine standard solution, mg/mL; V--volume of iodine standard solution consumed by titration sample, mL; V. --volume of iodine standard solution consumed by blank test, mL; -sample amount, g.
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