GB/T 5687.9-1988 Chemical analysis methods for ferrochromium - Combustion neutralization titration method for determination of sulfur content

This standard is applicable to the determination of sulfur content in ferrochrome. Determination range: ≤0.120%. This standard complies with GB 1467-78 "General Principles and General Provisions of Chemical Analysis Methods for Metallurgical Products". GB/T 5687.9-1988 Chemical Analysis Method for Ferrochrome - Determination of Sulfur Content by Combustion Neutralization Titration GB/T5687.9-1988 Standard Download Decompression Password: www.bzxz.net

National Standard of the People's Republic of China
Methods for chemical analysis of ferrochromium
Determination of sulfur content by combustion-neutralization titration method
Methods for chemical analysis of ferrochromiumThe combustion-neutralization titration method for thedetermination of sulfur contentThis standard applies to the determination of sulfur content in ferrochromium. Determination range: ≤0.120%. UDC 669.15'26
GB 5687.9--- 88
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 a 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: Φ×L, mm: 20~24×600. 2.3 Porcelain boat: pre-burn in a high temperature combustion tube at 1400℃ with oxygen for 5min, cool and set aside. 2.4 High purity iron: powder, sulfur content less than 0.0010%. 2.5 Vanadium pentoxide: sulfur content less than 0.0010%. 2.6 Silica gel, activated alumina or magnesium perchlorate. 2.7 Alkali or sodium hydroxide (granular). 2.8 Chromic acid saturated sulfuric acid: add potassium dichromate or anhydrous chromic acid to sulfuric acid (p1.84g/mL) to saturate it, and use the upper clear liquid. 2.9 Absorption liquid: transfer 3.5mL hydrogen peroxide (30%), dilute to 1000mL with water, and mix well. 2.10 Mixed indicator: weigh 0.1250g methyl red and 0.0830g methylene blue, dissolve in anhydrous ethanol and dilute to 100mL.
2.11 Aminosulfonic acid standard solution: weigh about 0.1000g (accurate to 0.1mg) of aminosulfonic acid (NHSOH) with a purity greater than 99.90% that has been dried in a vacuum sulfuric acid dryer 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 (NaOH) = 0.005mol/L. 2.12.1 Preparation
Weigh 0.2000g of sodium hydroxide and dissolve it in 1000mL of water, add 1mL of newly prepared saturated barium hydroxide solution, and mix well. Isolate it from carbon dioxide and place it for 2 to 3 days. Take the upper clear liquid when using it. 2.12.2 Calibration
Pipette 20.00mL of aminosulfonic acid standard solution (2.11) into a 250mL conical flask, add 100mL of 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 pure blue and remains blue for 30 seconds.
Approved by the Ministry of Metallurgical Industry of the People's Republic of China on February 2, 19883.16
Implemented on March 1, 1989
GB 5687.9—88
2.12.3 Perform a blank test with 120mL of water starting from the addition of 10 drops of bromothymol blue indicator (0.1%) as in 2.12.2. The concentration of the sodium hydroxide standard solution is calculated according to the formula (1): 1 000×m·×00
97.093×(V—V.)
Wherein: c
m·fx40
97.093×(V
is the molar concentration of the sodium hydroxide standard solution, mol/L; the amount of aminosulfonic acid weighed, nominal;
f--the purity of aminosulfonic acid, % (m/m); V
is the volume of the sodium hydroxide standard solution consumed during calibration, mL; the volume of the sodium hydroxide standard solution consumed during the blank test during 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--flow meter; 4--buffer bottle; 5--gas washing bottle, containing chromium Acid saturated sulfuric acid; 6-drying tower, filled with soda lime or sodium hydroxide (granular); 7-washing bottle, filled with sulfuric acid (p1.84g/mL); 8-drying tower, filled with silica gel activated alumina; 9-two-way piston; 10-high temperature combustion furnace (about 300mm long): 11-white dynamic temperature controller (with thermocouple), control the furnace temperature at 14001450℃; 12-high temperature combustion tube; 13-porcelain boat: 14-silica gel cold; 15-dehydrating tube; 16-absorption bottle (without floating beads); 17-reference solution; 18-micro burette 3.2 Absorption bottle See Figure 2:
4 Sample
GB 5687. 9—
4.1 All the micro-carbon ferrochrome, low-carbon ferrochrome and medium-carbon ferrochrome samples shall pass through a 1.68 mm sieve hole. 4.2 All the high-carbon ferrochrome samples shall pass through a 0.125 mm sieve hole. 5 Analysis steps
5.1 Sample quantity
Weigh 0.5000 g of sample.
5.2 Blank test
Perform a blank test according to 5.3 on a porcelain boat (2.3) pre-filled with 1 g of high-purity iron (2.4) and 0.25 g of vanadium pentoxide (2.5). 5.3 Determination
5.3.1 Connect all parts of the sulfur determination device and check the airtightness. Heat the high-temperature combustion tube (12) to raise the temperature inside the tube to 1400-1450 ℃.
5.3.2 Transfer 40mL of absorption solution (2.9) to 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 the carbon dioxide in the solution. If the solution is reddish purple at this time, add sodium hydroxide standard solution (2.12) until the solution is green.
5.3.3 Place the sample (5.1) in a pre-filled container containing 1g of high-purity iron (2 .4) in the porcelain boat (2.3), 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 (14) (pay special attention to the seal), and slightly introduce oxygen to prevent the absorption liquid from flowing back.
5.3.4 Let the sample burn for 5 minutes by introducing oxygen at a flow rate of 200mL/min, and then introduce the oxygen flow rate of 700~900mL/min (inlet 348
GB 5687.9--88bzxz.net
flow rate) into the absorption bottle (16) to absorb sulfur dioxide. After burning for 10 minutes, titrate with sodium hydroxide standard solution (2.12) until the solution changes from reddish purple to bright green, and then intermittently pass oxygen for 5 minutes at an oxygen flow rate of 1000~1200mL/min controlled by the two-way piston (9). If the solution is reddish purple, continue to titrate with sodium hydroxide standard solution (2.12) until it is bright green. Stop oxygen flow, and then use the above absorption liquid to wash the drying tube (15) and the pipes at the connecting parts, and introduce it into the absorption bottle. If the solution is reddish purple, continue to titrate with sodium hydroxide standard solution (2.12) until it turns bright green.
6 Calculation of analysis results
Calculate the percentage of sulfur according to formula (2):
S(%) = (V, - V) :e X 0. 016 03 X100
Where: V,—the volume of sodium hydroxide standard solution consumed when titrating the sample solution, mL, V.
the volume of sodium hydroxide standard solution consumed when titrating the blank test solution, mL; the molar concentration of the sodium hydroxide standard solution, mol/L; the sample volume, g:
0.01603——1.00mL1.000mol/L sodium hydroxide standard solution is equivalent to the molar mass of sulfur, g/mol. 7 Allowable Difference
The difference between the analysis results of laboratories shall not be greater than the allowable difference listed in the following table. Sulfur
>0. 005~0. 015
>0. 015~~ 0. 025
>0. 025～0. 045
>0. 045～0. 070
≥0. 070~0. 120
Additional Notes:
This standard was drafted by Hunan Ferroalloy Factory.
The main drafters of this standard are Zhang Yulan and Yin Dajian. Allowable Difference
From the date of implementation of this standard, the former Ministry of Metallurgical Industry Standard YB584-65 "Chemical Analysis Method of Ferrochrome" shall be invalid. (2)
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