GB/T 4324.27-1984 Chemical analysis of tungsten - Combustion-coulometric titration method for determination of carbon content

GB/T 4324.27-1984 Chemical analysis of tungsten - Combustion-coulometric titration method for determination of carbon content GB/T4324.27-1984 standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Chemical analysis method of tungsten
Determination of carbon content by combustion-coulometric titration
Methods for chemical analysis of tungstenThe combustion-coulometric titration nethod forthe determination of carbon contentThis standard is applicable to the determination of carbon content in dry tungsten. Determination range: 0.0005~0.50%. This standard complies with GB1467-8 "General Principles and General Provisions of Standards for Chemical Analysis Methods of Metallurgical Products". 1 Method Summary
UDC669.27:543
273:546. 26
GB4324.27-84
Carbon in the sample is burned into carbon dioxide in a high-temperature oxygen flow and introduced into a barium perfluoride solution with a pH of about 9.5. The perchloric acid produced reduces the pH value of the solution. Electrolysis is carried out by passing a certain pulse current to restore the pH value of the solution to its original value. According to the count of pulse current consumed during electrolysis, calculate the carbon content in the sample. During the combustion process, the sample may contain a small amount of sulfur, which is oxidized to sulfur dioxide and removed by silver vanadate. 2 Reagents and materials
Barium carbonate: Powder, fill the bottom of the anode tank. 2.1
2.2 Simple gas purification materials and reagents: molecular sieve (color change), potassium oxychloride. 2.3 Silver vanadate: Fill the desulfurization tube,
Cathode tank solution, weigh 100 grams of chlorinated perchlorate and 60ml of isopropanol, dissolve in 2000ml of water, and store in a ground-mouth bottle for use. 2.4
2.5 Anode tank solution: Weigh 100g of crystalline chlorinated perchlorate, dissolve in 500ml of water, and store in a ground-mouth bottle for use. 2.6 Reference electrode pool solution: Weigh 5g of perchloric acid and 3g of sodium chloride, dissolve in 100ml of water and add a few drops of 5% silver nitrate solution, store in a ground bottle for later use.
Pernitrogen acid wash solution (5%): used to clean the cathode pool. Porcelain tube: 22mm× 17mm × 6n0mm. 2.8
Porcelain boat: 88mm, oxygenated at 1200℃ for 10mia, taken out and placed in a lower flask for cooling. 2.9
Glass wool: filled in the dust collector.
Pigeon sample with known carbon content.
Oxygen: purity greater than 99%.
3 Instruments and equipment
3.1 Tubular combustion furnace: carbon silicon rod heating, double porcelain tube type, power not less than 3kW, maximum temperature can reach 1300℃. 3.2 Gas flow chart is shown in Figure 1. Oxygen is burned through the first porcelain tube to remove carbon, and then absorbed by the potassium hydroxide tube, the color changes and the sieve absorbs water, and then enters the second porcelain tube to burn the sample. Carbon is burned to generate carbon oxide: it is carried away by oxygen, passes through the dust removal tube and the desulfurization tube, enters the absorption cup of the coulometric analyzer and is then discharged. The air inlet end of the second porcelain tube is connected to the sample adding device shown in Figure 2 to prevent the increase and fluctuation of the system blank value caused by the entry of air when the sealing rubber stopper of the porcelain tube mouth is opened. National Standard Week 1984 04-11 Release
10 sets 6~03-01 implementation
GB 424.27
Figure 1 Schematic diagram of gas flow
1-oxygen cylinder 12-pressure regulating valve, 3-potassium hydroxide tube, 4-gas storage cylinder (5L), descending sensor protection, 6-porcelain boat, 7-grade potassium oxide tube, 8-color-changing molecular sieve tube 9 (1): 9 (2), 9 (3) Needle-shaped width 10 (1), 102) 10 (3) - flow meter: 11 - glass piston, 12 - dust collector; 13 - desulfurization pipe 14 - diverter valve, 15 - diverter pump 16 - solenoid valve: 17 - absorption electrolysis cup Figure 2 Sample port
1 - rubber stopper, 2 - glass sample port, 3 - oxygen inlet, 4 - vacuum black wax, 5 - cooling water inlet 16 cooling water outlet! 1,? - porcelain tube 3.3 Auto-coupling regulator: single-phase 0~250V, 3kW, used to adjust the furnace temperature. 3 .4 Electric voltage regulator, 1kw, used to stabilize the power supply voltage of the coulometric analyzer. 1o
3.5 Coulometric analyzer: The schematic diagram of the coulometric titration circuit is shown in Figure 3. The pulse current of the absorption electrolysis cup is generated by the charge and discharge circuit. When the charge and discharge capacitor in the circuit is charged to a certain voltage, it is connected to the electrolysis electrode, and the charge on the capacitor passes through the absorption liquid in the form of an electrolysis pulse current, which is equivalent to 0.5×10- of carbon. 4324 27--84
Figure 3 Schematic diagram of coulometric titration circuit
1.-Cathode filter [including stirrer, glass electrode, platinum electrode (anode)]: 2-Anode core [platinum electrode (anode)]: 3-Reference electrode pool (silver-silver chloride electrode), 4-pH electrode: 5-Control circuit: 6-Pulse frequency control circuit 17-Charge and discharge circuit: 8-Counting display circuit, 9 Constant current irrigation
.1 Block sample is placed in a clean carbide mortar and crushed into 40-80 mesh. 2 Powdered sample does not need to be processed, but needs to be stored in a glass bottle with a ground stopper, sealed or stored in a card desiccator. Storage time does not exceed 3 Months.
Analysis steps
5.1 Determination quantity
During analysis, a sample should be weighed for determination. The measured value should be within the allowable difference in the room, and the average value should be taken. 5.2 Sample quantity
Weigh the sample quantity according to Table 1 and spread it on the bottom of the porcelain boat. Table 1
0.01 ~ :0. 05
0.05~0.10
0.10 ~0.80
5.3 Instrument preparation
5.3.1 Check the tightness of each part of the gas circuit. Sample volume, g
5.3.2 Set the four-way diverter valve to the 1:1 position, the two-way glass piston 11 to the open position, and the oxygen cylinder is always on. Adjust the reading (reading) and needle valve 9 (1), 9 (2), 9 (3) to make the total oxygen flow rate about .8L/mi, the oxygen flow rate above the absorption liquid is 200ml/min, and the oxygen flow rate for the tubular combustion furnace is 150ml/min. 5.3.3 Turn on the power supply, gradually increase the voltage of the self-regulator, and gradually raise the temperature of the tubular combustion furnace to 1250~1300℃. Ma this company, 95
GB 4324.27-84
At the same time, turn on the power supply of the coulometric analyzer and let the instrument work stably. 5.4 Calibration of the instrument
5.4.1 After the instrument has been running for about 1 hour, collect the counts of the electrolytic pulse current passing through the absorption liquid within 1 minute, which is the background blank of the gas system. Generally, it should be less than 1 count and stable. 5.4.2 Adjust the counting frequency of the pulse current passing through the absorption liquid so that 1 or 2 pulse currents are displayed each time. Repeat the titration end point calibration of the pH circuit several times to make the absorption liquid pH about 9.5. 5.4. Use a constant current device to perform an electrometric calibration on the electrolytic pulse current of the coulometric titration so that when 1 coulomb of charge passes through the absorption cup from the constant current instrument, the pulse current count displayed during electrolysis is between 124 and 128. The charge of each pulse current is equivalent to less than 0.5×10-g carbon. 5.4.
Measure the tungsten sample with a known carbon content in the same steps as the sample analysis. The analysis result should be within the allowable error. Blank test
Along with the sample, continuously measure the blank values ​​of three porcelain boats and take the average value as the blank value of the analysis. The value should be less than 10 counts and the fluctuation should not exceed 2 counts.
5.6 Determination
5.6.1 Close the two-way glass piston 11, open the rubber stopper of the sample inlet, place the porcelain boat containing the sample at the mouth of the porcelain tube, use a special nickel-chromium alloy rod to quickly push the porcelain boat to the high temperature area of ​​the tube, and immediately plug the rubber stopper. 5.6.2 Wait until the float of the flowmeter 10 (3) returns to its original position (about 1 to 2 minutes), the sample is completely oxidized and burned in the oxygen flow, and carbon is converted into carbon dioxide. Open the two-way glass piston 11, calculate the suction time according to the stopwatch and start counting the pulse current. 5.6.3 The gas produced by the combustion reaction is carried away by the oxygen flow, and after dust removal and sulfur removal, it enters the absorption electrolysis cup for coulometric titration. After 3 minutes, the system returns to the original background value, the electrolysis is completed, and the pulse current count displayed on the digital tube is read. 6 Calculation of analysis results
Calculate the carbon content according to the following formula:
C (%) = (4- B) × 0.5 × 10-6
-the average value of the electrolytic pulse current obtained when analyzing the sample. B is the average value of the electrolytic pulse current obtained when analyzing the blank value of the porcelain boat. m-sample amount, gs
0.5 × 10 6--
7 Allowable difference
-each pulse current village is equivalent to the mass of carbon. The difference between the analysis results of the experimental space should not be greater than the allowable difference listed in Table 2. Table 2
0.0005 ~-:0.0010
0,0010 ~20.0030
0.0030 ~ *:0,0090
Allowance
AllowancewwW.bzxz.Net
0.009~≤.0.015
0.015-.0.040
0.040~0.100
0.100~,0.500
Additional Notes:
GB 4324-27--84
This standard was proposed by the Ministry of Metallurgical Industry of the People's Republic of China. This standard was drafted by Zhuzhou Cemented Carbide Co., Ltd. This standard was drafted by Zhuzhou Cemented Carbide Co., Ltd. The main drafters of this standard are Wang Shuifa and He Kehong. As of the date of implementation of this standard, the source metallurgical standard YB895--77 "Chemical Analysis Method for Tungsten" shall be invalid.
Tip: This standard content only shows part of the intercepted content of the complete standard. If you need the complete standard, please go to the top to download the complete standard document for free.