JB/T 7948.2-1999 Chemical analysis methods for melting fluxes - Determination of manganese oxide content by potentiometric titration
Some standard content:
JB/T7948.2--1999
This standard is equivalent to TOCT22978.1~22978.10-78 "Method for Chemical Analysis of Melting Flux". "Determination of Manganese Oxide Content by Potentiometric Titration". The revision of this standard is an editorial modification of JB/T7948.2-95 "Method for Chemical Analysis of Melting Flux". Its technical content has not changed. This standard replaces JB/T7948.2--95 from the date of implementation. Appendix A of this standard is the appendix of the standard. This standard is proposed and managed by the National Technical Committee for Welding Standardization. The drafting unit of this standard: Harbin Welding Research Institute. The main drafters of this standard: Lin Kegong and Bai Yun. 351wwW.bzxz.Net
Standard of the Machinery Industry of the People's Republic of China
Methods for chemical analysis of melted welding fluxes
Determination of manganese oxide content by potentiometric titration
Methods for chemical analysis of melted welding fluxesJB/T 7948.2--1999
Replaces JB/T7948.2-95
The potentiometric method for determination of manganese oxide content1Scope
This standard is applicable to the determination of manganese oxide content in melted welding fluxes. The determination range is 2.0% to 50.0%. This standard complies with GB/T1467-1978 "General Principles and General Provisions for Chemical Analysis Methods of Metallurgical Products". 2Cited 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/T1467—1978. General principles and general provisions of the standard for chemical analysis methods of metallurgical products 3 Method summary
This method is based on the fact that divalent manganese ions are oxidized to trivalent by potassium permanganate solution in the presence of sodium pyrophosphate in a neutral or weakly alkaline medium, and a potential jump occurs at the equivalence point, indicating the end of the reaction. The percentage of manganese oxide is measured in this way. 4 Reagents
4.1 Sodium potassium carbonate.
4.2 Potassium pyrosulfate.
4.3 Hydrochloric acid (specific gravity 1.19).
4.4 Perchloric acid (70%).
Hydrofluoric acid (40%).
Ethanol (99.5%).
Hydrochloric acid (1+1).
Hydrochloric acid (1+1): saturated with boric acid at 20°C. Hydrochloric acid (5+95): heated to 70~80°C when used. 4.9
Sulfuric acid (1+1).
Ammonium hydroxide (1+1).
Sodium pyrophosphate solution: weigh 70g sodium pyrophosphate (NazP0,?10H20) and dissolve it in appropriate amount of water, dilute it with water to 1000mL, and mix it. Sodium nitrite solution (2%).
Animal glue solution: weigh 1g animal glue and dissolve it in 100mL boiling water. 4.15
Neutral red solution: weigh 0.1g neutral red and dissolve it in 60mL ethanol (4.6), add 40ml water, and mix it. 4.16 Manganese standard solution: Weigh 0.5000g of metallic manganese (99.99%) and place it in a 250ml conical cup, add 10ml of hydrochloric acid (4.3), approved by the Canadian Guohao Machinery Industry Bureau on June 24, 1999 352
2000-01-01 implementation
JB/T 79482-1999
heat to dissolve, cool. Transfer to a 500mL volumetric flask, add 40mL of hydrochloric acid (4.3), dilute to the mark with water, and mix. This liquid contains 1.0mL of manganese in 1mL.
4.17 Potassium permanganate standard solution (about 0.02N). Calibration: Take three portions of 10.00 mL of manganese standard solution (4.16) and place them in 300 mL graduated beakers respectively. Add 100 mL of water and 100 mL of sodium pyrophosphate solution (4.12). Add 3 drops of neutral red indicator (4.15). Use ammonium hydroxide (4.11) to neutralize the solution from red to dark brown. Add water to dilute to about 250 mL. Place the beaker on a potentiometric titrator, put down the electrode, start the stirrer, and titrate with potassium permanganate standard solution (4.17) until the potential of the solution changes suddenly. Calculate the titration degree of potassium permanganate standard solution (4.17) on manganese oxide according to formula (1): T=+
Wherein: m--the amount of manganese equivalent to the manganese standard solution (4.16) transferred, g, (1)
the average volume of potassium permanganate standard solution (4.17) consumed during titration (if the extreme difference exceeds 0.10mL, it should be recalibrated), mL;
T--the amount of manganese equivalent to 1 mL potassium permanganate standard solution (4.17), g1.291-
5 instrument dew
the conversion factor of manganese converted to manganese oxide.
5.1 Potentiometric titrator (with electric stirrer). 5.2 Electrodes: The cathode is a platinum electrode; the anode is a calomel electrode. 6 Sample
The sample should pass through a 200-mesh sieve. Pre-dry at 105-110℃ for 1h, place in a desiccator and cool to room temperature. 7 Analysis steps
7.1 Determination quantity
Three samples should be weighed for determination during analysis and the average value should be taken. 7.2 Sample quantity
Weigh 0.5000g of sample.
7.3 Determination
7.3.1 Place the sample (7.2) in a platinum pot containing 4g potassium sodium carbonate (4.1), mix, cover with 2g potassium sodium carbonate (4.1), and cover. Transfer to a high-temperature furnace at 1000℃±20℃ and melt for 30min. Take out and cool. 7.3.2 Wipe the outer wall of the crucible with filter paper, place it in a 300mL beaker, cover with blood, add 50mL hydrochloric acid (4.7), heat for a period of time, and after the molten block is dissolved, wash with water and take out the crucible.
7.3.3 Heat the solution (7.3.2) and evaporate it until the salts are precipitated, add 10mL of animal glue solution (4.14) and 40mL of water, stir for 3~5min, and keep warm at low temperature (50℃) for 10min. Remove it, filter it with medium-speed quantitative filter paper, wash the beaker with hot hydrochloric acid (4.9) and wash the precipitate 6~8 times, and then wash the precipitate with hot water 4~5 times. Save the filtrate (main solution). 7.3.4 Place the filter paper and the precipitate in a platinum crucible, dry and ashed, and transfer it to a high-temperature furnace at 1000℃±20℃ and burn it for 15min. Take it out and cool it. Add a small amount of water to moisten the precipitate, add 5~10 drops of sulfuric acid (4.10), add 5~8mL of hydrofluoric acid (4.5), and heat it until the white smoke disappears. Transfer it to a high-temperature furnace at 1000℃±20℃ and burn it for 5min, take it out and cool it. 7.3.5 Add 1~2g potassium pyrosulfate (4.2) to the crucible, cover the crucible, place it on an alcohol burner to melt until the residue is completely decomposed, remove it, and cool it. Wipe the outer wall of the crucible with filter paper, place it in a 150mL beaker, add 5~10mL hydrochloric acid (4.7), heat until the molten block is melted, wash it with water, remove the crucible, and cool it. Combine this solution with the main solution, transfer it to a 250mL volumetric flask, dilute it to the scale with water, and mix it well. This is used to determine manganese oxide, aluminum oxide, iron oxide, phosphorus, calcium oxide, and magnesium oxide. 353
JB/T 7948. 2--1999
7.3.6 Take 25.00 mL of solution (7.3.5) and put it into a 300 mL measuring beaker containing 100 mL of sodium pyrophosphate solution (4.12). Add 3 drops of neutral red indicator (4.15). Neutralize with ammonium hydroxide (4.11) until the solution changes from red to dark brown. Dilute with water to 250 ml. Place the beaker on a potentiometric titrator, put down the electrode, start the stirrer, and titrate with potassium permanganate standard solution (4.17) until the potential of the solution changes suddenly.
8 Calculation of analysis results
Calculate the percentage of manganese oxide according to formula (2): VT
Wherein, V—volume of potassium permanganate standard solution (4.17) consumed during titration, mL; T—amount of manganese oxide equivalent to 1 mL potassium permanganate standard solution (4.17), g; amount of test solution (7.3.6) equivalent to the sample, g. 9 Allowable difference
The difference between the results of parallel determinations should not be greater than the allowable difference listed in Table 1. Table 1 Allowable difference
Manganese oxide
2.0～5.0
>5. 0~10. 0
>10.0~25.0
>25.0~50.0
Allowable difference
JB/T7948.2--1999
Appendix A
(Appendix of Standard Male)
Acid Dissolution Method
A1 For samples that can be decomposed by acid, the following analysis method can be used. A1.1 Place the sample (7.2) in a 250mL porcelain evaporator with a handle, add 5mL hydrochloric acid (4.8) and 20mL hydrochloric acid (4.3) and 20mL perfluoric acid (4.4), cover with blood, and heat to dissolve. After the sample is completely dissolved, evaporate the solution to nearly dryness, cool it slightly, add 10mL perchloric acid (4.4), and evaporate it to nearly dryness. Cool it, add 5mL hydrochloric acid (4.7), heat to dissolve the salts, and add 30~~40mL hot water. If the liquid is rose-colored, add a few drops of sodium nitrite solution (4.13) to fade the color. A1.2 Filter with medium-speed quantitative filter paper, wash with hot hydrochloric acid (4.9) and evaporate and wash the precipitate 6 to 8 times, then wash the precipitate with hot water 8 to 10 times. Save the filtrate (main solution), and precipitate according to steps 7.3.4 to 7.3.5. A7.3 Transfer 25.0 mL of solution (A1.2) and operate according to steps 7 and 3.6.
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