This standard is applicable to the determination of sulfur content in metallic chromium. Determination range: ≤0.07%. This standard complies with GB 1467-78 "General Principles and General Provisions of Chemical Analysis Methods for Metallurgical Products". GB/T 4702.17-1988 Metallic chromium chemical analysis method Combustion neutralization titration method for determination of sulfur content GB/T4702.17-1988 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Methods for chemical analysis of chromium metal
Determination of sulfur content by combustion neutralization titration
Mcthods for chemical analysis ol chronliun meta!The cornbustion-neutralization titration method for thcdeterminetlon of sulfur contentThis standard applies to the determination of sulfur content in chromium metal. Determination range: ≤0.07%. UDC 669.26
GB4702.17-88
This standard complies with GB1167:78 "General Principles and General Provisions for Chemical Analysis Methods for Metallurgical Products". 1 Summary of the method
The sample is burned in an oxygen stream to oxidize all sulfur to sulfur difluoride, 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 back: ±×L, mm, 20~24×6002.3 Porcelain boat: pre-burn in a high temperature combustion tube at 1400℃ with oxygen for 5 minutes, cool and set aside. 2.4 High purity iron: 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 lime or sodium hydroxide (granular). 2.8 Chromic acid saturated sulfuric acid: add dichromic acid or anhydrous chromic acid to sulfuric acid (p1.84%/mL) to saturate it, and use the upper clear liquid. 2.9 Absorption liquid: transfer 3.5mL hydrogen peroxide (30%) and dilute it to 1000mL with water, mix. 2.10 Mixed indicator: Weigh 0.125 g of methyl red and 0.083 g of methylene blue, dissolve in anhydrous ethanol and dilute to [00 mL]. 2.11 Aminosulfonic acid standard: Weigh about 0.100 g (accurate to 0.1 mg) of aminosulfonic acid (NH, SO, H) which has been dried in a vacuum sulfuric acid dryer for about 48 hours and has a purity greater than 99.90% in a 300 mL beaker, dissolve it completely in 30 mL of water, transfer it to a 500 mL brown volumetric flask, dilute to the mark with water, and mix well.
2.12 Sodium hydroxide standard solution; c(NaOH)=0.005mol/L2.12.1 Preparation
Weigh 0.200 ml sodium hydroxide and dissolve it in 100 ml water. Add 1 ml of freshly prepared saturated sodium hydroxide solution and mix well. Isolate the solution from carbon dioxide and let it stand for 2-3 days. Take the clear liquid from the top when using. 2.12.2 Calibration
Pipette 20.00 ml aminosulfonic acid standard solution (2.11) into a 250 ml can, add 100 ml water and 10 drops of thyme blue indicator (0.1%), and immediately titrate with sodium hydroxide standard solution (2.12.1) until the can liquid changes from yellow to pure blue and keeps for 3 Approved by the Ministry of Metallurgical Industry of the People's Republic of China on February 2, 1988 and implemented on March 1, 1989
The end point is not reached.
GB 4702. 17
2.12.3 Use 120 ml of water to perform a blank test starting from the addition of 10 drops of bromocresol blue indicator (0.1%) as in 2.12.2. Calculate the iridium degree of the sodium hydroxide standard solution according to formula (1): 1000×mf×0
mf×40
e 97. 093 × (Vw)= 97 093 × (,-) In the formula, c\—the molar concentration of the sodium hydroxide standard solution, mol/L; the weighing basis of the aminosulfonic acid
f——the purity of the aminosulfonic acid, % (m/m); the volume of the sodium hydroxide standard solution consumed in the calibration, mL, the volume of the sodium hydroxide standard solution consumed in the calibration time-space test, mL; 97.093-
the molar mass of the aminosulfonic acid, B/mol.
3 Apparatus and device
3.1 Sulfur determination device See Figure 1
1 oxygen cylinder, 2 oxygen pressure gauge, 8 flow meter, 4 buffer bottle, 5 washing bottle, containing chromic acid saturated acid, 6 dry coal tower, containing soda lime or oxygen Sodium hydroxide (granular), 7-gas washing bottle-containing ethanol (p1.H4g/mL), 8-drying tower, containing silica gel, activated alumina + 9-two-way piston: 10-high temperature combustion furnace (about 300mm long); 11-automatic temperature controller (with thermocouple>. Keep the temperature at 1400~1150C): 12-high temperature combustion tube 13-ceramic plate! 14-silica gel plug: 15-dry coal pipe; 16-collecting bottle (without floating), 17-reference solution: 18-micro-disc burette 3.2 Absorption bottle see Figure 2
4 Sample
The sample should all pass through the 1.68mm hole.
5 Analysis steps
5.1 Sample quantity
Weigh 0. 500 0 g sample.
GB 4702. 17—88
5.2 Blank test
Put a porcelain boat (2,3) pre-filled with 1 g high-purity iron (2.4) and 0.25 g vanadium dioxide (2.5) into a blank test according to 5.3. 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 1400~1150C. 5.3.2 Transfer 40 mL of the 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 700~900 mL/mlm for about 5 minutes to drive out the carbon dioxide in the solution. If the bath liquid 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). Then push it into the central high-temperature part of the high-temperature combustion tube (12), plug it tightly with the silicone plug (14) (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 make the sample burn for 5min, then introduce oxygen at a flow rate of 700~900mL/min (inlet flow rate) into the absorption bottle (16) to absorb sulfur monoxide. After burning for 10min, titrate with sodium hydroxide standard solution (2.12) until the solution changes from red purple to bright green, then pass oxygen at a flow rate of 1000~1200mL/mln, and pass oxygen for 5min controlled by the two-way piston (9). If the solution is red purple, continue to titrate with sodium hydroxide standard solution (2,12) until it is bright green. Stop passing oxygen, and then use the above absorption liquid to wash the pipe at the connection part of the drying tube (15), 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 is bright green.
6 Calculation of analysis results
Calculate the percentage of sulfur according to formula (2):
(F,V) c× 0. 016 03 × 100
Wherein:
0. 016 03-
7 Allowable difference
The volume of sodium hydroxide standard solution consumed when titrating the sample solution, mL; The volume of sodium hydroxide standard solution consumed when titrating the blank test solution, mL, The molar concentration of sodium hydroxide standard solution, mol/L; Sample volume:bzxz.net
1.00mL1.000mal/LSodium hydroxide standard solution is equivalent to the molar mass of sulfur + g/mat. The difference in analysis results between laboratories should not be greater than the allowable difference listed in the following table. Bowl
>0.005~~0.015
>D.015~0.025
>0.025~0.045
>0.045~~0.070
Additional remarks:
This standard was drafted by Hunan Ferroalloy Factory.
The main drafters of this standard are Zhang Yulan and Yin Dajian.
From the date of implementation of this standard, the former Ministry of Metallurgical Industry Standard YB582-65 "Methods for Chemical Analysis of Chromium" shall be invalidated. The level mark of this standard is GB4702.17-881(2)
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