This standard is applicable to the determination of sulfur content in silicon-chromium alloys. Determination range: ≤0.025%. This standard complies with GB 1467-78 "General Principles and General Provisions for Chemical Analysis Methods of Metallurgical Products". GB/T 4699.7-1988 Chemical Analysis Method for Silicon-Chromium Alloys Combustion Neutralization Titration Method for Determination of Sulfur Content GB/T4699.7-1988 Standard Download Decompression Password: www.bzxz.net

National Standard of the People's Republic of China
Methods for chcmicel analysis of silleochromiumThe combustion-neutrallzation titration method for thedeterminstion ol gulfur contentThis standard is applicable to the determination of sulfur content in silleochromium alloys. Determination range: ≤0.025%, UDC 669.782'26
GB 4699.788
This standard complies with GB1467 "78 "General Principles and General Provisions for Chemical Analysis Methods of Metallurgical Products". 1 Method Summary
The sample is burned in an oxygen stream to oxidize all sulfur into sulfur dioxide, which is absorbed in hydrogen peroxide solution to become sulfuric acid, and titrated with a sodium hydroxide standard solution.
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. 2.1 Oxygen: purity greater than 99.5%.
2.2 High-temperature combustion tube: × L, mm: 20~24×6002.3 Porcelain boat: pre-burned in a high-temperature combustion tube at 1400C with oxygen 5min. Cool and set aside. 2.4 High purity iron: powdered. Sulfur content less than 0.0010%. 2.5 Vanadium pentahydrate: content less than 0.0010%. 2.6 Silica gel, activated alumina or magnesium perfluorite. 2.7 Soda lime or sodium hydroxide (granular). 2.8 Chromic acid saturated sulfuric acid, add potassium dichromate or anhydrous sodium hydroxide to sulfuric acid (1.84g/mL) to saturate it, use the upper clear liquid. 2.9 Absorption liquid: transfer 3.5mL hydrogen peroxide (30%) and dilute to 1000mL with water. Mix, 2.10 Mixed indicator: weigh 0.1250g methyl red and 0.0830g methylene blue, dissolve in anhydrous ethanol and dilute to 100mL. 2.1 1 Aminosulfonic acid standard solution: weigh about 0.100g (accurate to 0.1mg) of aminosulfonic acid (NHS0,H) with a purity greater than 99.90% that has been dried in a vacuum sulfuric acid + desiccator for about 48 hours in a 300ml beaker, dissolve it completely with 30mL of water, transfer it to a 500mL brown volumetric flask, dilute to the mark with water, and mix well. 2.12 Sodium hydroxide standard solution: c (Na0H) = 0.005mol/L. 2.12.1 Preparation
Weigh 0.200?g of sodium hydroxide and dissolve it in 1000mL of water, add 1mL of newly prepared saturated barium hydroxide solution, mix, isolate it from carbon dioxide and let it stand for 2 to 3 days. Take it out when using. The upper clear liquid. 2.12.2 Calibrationwww.bzxz.net
Pipette 20.00ml aminosulfonic acid standard solution (2.11) into a 250ml conical flask, add 100ml water, add 10 drops of bromothymol blue indicator (0.1%), and immediately titrate with sodium hydroxide standard solution (2.12.1) until the solution changes from yellow to blue and remains unchanged for 30s.
2.12.3 Use 120ml water to perform a blank test as in 2.12.2 starting from the addition of 10 drops of bromothymol blue indicator (0.1%). Approved by the Ministry of Metallurgical Industry of the People's Republic of China on February 2, 1988 and implemented on March 1, 1989
CB 4699.7—88
Calculate the concentration of the sodium hydroxide standard solution according to formula (1): 100: ×m
m*f×40
97.093 × (= 97.093 × (V) Where: -
the molar concentration of the sodium hydroxide standard solution, ol/Ln ---the weighed amount of aminosulfonic acid, 8;
-the purity of aminosulfonic acid, % (m/m)); -the volume of the sodium hydroxide standard solution consumed during the calibration, mL! -the volume of the sodium hydroxide standard solution consumed in the blank test during the calibration, mL; the molar mass of aminosulfonic acid, g/mol.
3 Instruments and devices
3.1 Sulfur determination device See Figure 1;
1—Oxygen cylinder, 2—Oxygen pressure gauge; 3—Flowmeter + 4 Buffer bottle: 5—Gas washing bottle + chromic acid saturated sulfuric acid, 6—Drying tower + soda lime or sodium hydroxide (granular) 7—Gas washing bottle, sulfuric acid (μ 1.84 s/mL), 8—Drying tower, silica gel, activated alumina, 9—Two-way piston 10—High-pressure combustion furnace (about 300 mm long); 1—Automatic temperature controller (with thermoelectric regulator), control the furnace temperature at 1400~1450 ℃; 12 High temperature combustion tube; 13-- Porcelain pair; 14-- Silicone plug; 15-- Drying back: 16-- Collection bottle (without floating beads); 17-- Reference solution: 18-- Micro-burette 3.2 Absorption bottle See Figure 2:
4 Sample
All samples should pass through 0.125mm sieve.
5 Analysis steps
5.1 Sample quantity
Weigh 0.500 0 g sample.
5.2 Blank test
GB 4699.7-88
Carry out a blank test on the porcelain boat (2.3) which has been pre-filled with 1B high purity iron (2.4) and 0.25 vanadium pentoxide (2.5) according to 5.3. 5.3 Determination
5.3.1 Connect all parts of the sulfur determination device and check the air tightness. Heat the high-temperature combustion tube (12) to raise the temperature inside the tube to 1400~～1450°C.
5.3.2 Transfer 40mL of absorption liquid (2.9) into the absorption bottle (16), add 5 drops of mixed indicator (2.10), and pass oxygen at a flow rate of 700~900mL/min for about 5min to drive out sulfur dioxide in the solution. If the solution is reddish purple at this time, add sodium hydroxide standard solution (2.12) until the solution is bright green.
5.3.3 Place the sample (5.1) in a porcelain boat (2.3) pre-filled with 1g of high-purity iron (2.4), and then cover it with 0.25g of vanadium pentoxide (2.5), and then push it into the central high-temperature part of the high-temperature combustion tube (12), plug the silicone plug (11) tightly (pay special attention to the seal), and slightly pass oxygen to prevent the absorption liquid from flowing back.
5.3.4 Pass oxygen at a flow rate of 200mL/min to allow the sample to burn for 5min, and then introduce oxygen at a flow rate of 700~900mL/min (inlet amount) into the absorption bottle (16) to absorb sulfur dioxide. After burning for 15min, titrate with sodium hydride standard solution (2.12) until the solution changes from red GB 4699. 788
Purple turns to bright green, then oxygen is passed through the two-way piston (9) at an oxygen flow rate of 1000-1200mL/min for 5 minutes. If the solution is red-purple, continue to titrate with sodium hydroxide standard solution (2.12) until it fades, stop passing oxygen, and then use the above-mentioned absorption to wash the dry fuel (15) and the pipeline of the connecting part, and introduce it into the absorption bottle. If the solution is red-purple, continue to titrate with sodium hydroxide standard solution (2.12) until it turns bright green as the end point.
6 Calculation of analysis results
Calculate the content of sparse nutrient according to formula (2):
5(%)==-×0.016 03 × 100
Where V…The volume of sodium hydroxide standard solution consumed when titrating the sample solution, mLThe volume of sodium hydroxide standard solution consumed when titrating the blank test solution, mL,The molar concentration of sodium hydroxide standard solution, mul/L; 0.016 03
7Allowance
Sample volume + B,
1.00 mL1.000 mol/L sodium hydroxide standard solution is equivalent to the molar mass of sulfur, g/mol. The difference between the analysis results of laboratories should not be greater than the allowable difference listed in the following table. Allowable difference
>0. 005 ~0. 015
>0, 015~-0. 025
Additional remarks:
This standard was drafted by Chaonan Ferroalloy Factory.
The main drafters of this standard are Zhang Yulan and Yin Dajian, 0. 001
From the date of implementation of this standard, the former Ministry of Metallurgical Industry Standard YB577-65 Chemical Analysis Method for Silicon-Chromium Alloy will be invalid. This standard water grade mark GB4699.7881
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