JB/T 9220.7-1999 Chemical analysis methods for acidic slag from foundry cupola furnaces - Determination of calcium oxide content by potassium permanganate volumetric method
Some standard content:
JB/T9220.7-1999
This standard is a revision of JB/Z284.7:87 "Chemical Analysis Methods for Acidic Slag of Cast Iron Furnace". During the revision, editorial changes were made to the original standard, and the main technical content remained unchanged. This standard replaces JB/Z284.787 from the date of implementation. This standard is proposed and managed by the National Foundry Standardization Technical Committee. Potassium permanganate volumetric method for measuring calcium oxide
The drafting units of this standard: Shanghai Diesel Engine Factory, Nanchang Diesel Engine Factory, Guiyang Foundry, Shenyang Foundry, Shanghai Tractor Company, Huaka Steel Plant, Wuxi Diesel Engine Factory, Changzhou Diesel Engine, etc. The main drafters of this standard: Wang Zhihan, etc. 444
1 Scope
Machinery Industry Standard of the People's Republic of China
Chemical analysis methods for acid slay of cupola-Determination of calcium oxide by volumetricmethod using potassium permanganateJB/T 9220.7 1999
Replaces JB/Z284.7-87
This standard specifies the determination of calcium oxide content in chemical analysis methods. Determination range: 5.00%~45.00%. This standard is applicable to the analysis of the composition of acidic slag in foundry cupola furnaces. 2 Test conditions
The sample is dissolved in hydrochloric acid and chlorofluoric acid to evaporate silicon. Nitric acid and perchloric acid are used to drive out fluoride ions by fuming. Ammonium hydroxide-ammonium persulfate precipitation is used to separate interfering elements such as iron, aluminum, manganese, titanium, and phosphorus, and then calcium ions are precipitated as calcium oxalate. After filtration, washing, and dissolution in sulfuric acid, it is titrated with potassium permanganate standard solution.
3 Reagent preparation
Hydrochloric acid (density 1.19g/mL).
Hydrochloric acid (1+1).
Hydrogen Fluoric acid (density 1.15 g/mL).
Nitric acid (density 1.42 g/ml.).
Perchloric acid (density 1.67 g/mL).
Ammonium hydroxide (1 + 1).
Ammonium hydroxide (1 + 3).
Ammonium persulfate.
Ammonium nitrate solution (1%).
Sodium nitrite solution (2%).
Methyl red solution (0.1%): prepared in anhydrous ethanol . Ammonium oxalate solution (5%).
Ammonium oxalate solution (0.25%).
Silver nitrate solution (1%).
Sulfuric acid (1+3).
Potassium permanganate standard solution
3.16.10.1000N, weigh 3.2g potassium permanganate, dissolve it in a small amount of water, heat to a slight boil, cool to room temperature, filter it into a 1000ml brown volumetric flask with a glass crucible, dilute it to the mark with water, and mix. Place in dark place: calibrate after one week. 3.16.2 Calibration: Accurately weigh 0.2000g of sodium oxalate (reference reagent) dried to constant weight at 105°C in three portions, place them in 400ml beakers respectively, add 100ml of water and 25ml of sulfuric acid (3.15), heat to 80~90°C, and titrate with the prepared potassium permanganate standard solution until a slightly reddish color appears and does not disappear for 0.5min. The extreme difference of the number of milliliters of sodium permanganate standard solution consumed in the titration of three portions of sodium oxalate shall not exceed 0.05 ml. Take the average value and perform the empty door test together with the calibration.
The equivalent concentration of potassium permanganate standard solution is calculated according to formula (1): mX2000Www.bzxZ.net
N= 134X(VV)
Wherein: N---the equivalent concentration of potassium permanganate standard solution; m--the amount of sodium oxalate accurately weighed, g;
V. The average volume of potassium permanganate standard solution consumed during calibration, mL, V. The volume of potassium permanganate standard solution consumed in the blank test, ml. 134----the molecular weight of sodium oxalate.
4 Analysis steps
4.1 Sample amount
Weigh 0.5000g of sample.
4.2 Blank test
Perform a blank test with the sample.
4.3 Determination
（1）
4.3.1 Place the sample (4.1) in a 250ml polytetrafluoroethylene beaker, moisten the sample with a small amount of water, add 20ml hydrochloric acid (3.1) and 10ml hydrofluoric acid (3.3), heat at low temperature to dissolve, remove and cool slightly after part of the sample has dissolved, add 5ml nitric acid (3.4) and 10ml perfluoric acid (3.5), heat until thick white perchloric acid smoke is emitted for 5-10 minutes, remove and cool, rinse the wall of the beaker with water, add 2ml perchloric acid (3.5), continue heating and emit thick white perchloric acid smoke until 23ml solution remains in the beaker. Note: The temperature of the sample for heating and decomposition should not be too high. The heating and dissolution time generally takes about 30 minutes. 4.3.2 Remove and cool, rinse the inner wall with water, add 10ml of hydrochloric acid (3.2), heat and dissolve the salts, remove and cool, transfer the solution to a 500ml beaker, add water to a solution volume of about 150mL, 4.3.3 Boil, remove, add ammonium hydroxide (3.6) dropwise until the hydroxide precipitates, then add ammonium hydroxide (3.7) dropwise to adjust to pH 5~~6 (check the pH value with pH test paper), add 1g of ammonium persulfate (3.8), boil, precipitate manganese monoxide, and keep it boiling for 4~5 minutes. Continue to adjust to pH 5~~6 with ammonium hydroxide (3.7), boil, immediately filter with fast filter paper into a 500mL beaker, and wash the beaker and precipitate twice with hot ammonium nitrate solution (3.9).
1 Add ammonium hydroxide slowly, add while stirring, and make the reaction complete. 2. Boil the solution to destroy the ammonium persulfate. At this time, the sulfuric acid concentration increases, the acidity rises, and it is easy to dissolve part of the manganese oxide again. The pH value should be checked with pH test paper before filtering to ensure the precipitation and separation of manganese. 4.3.4 Unfold the filter paper and stick it to the inner wall of the original beaker. Use 10ml of hot hydrochloric acid (3.2) to dissolve the precipitate. Add sodium nitrite solution (3.10) dropwise until the red-brown color of the solution fades. Heat until the precipitate is completely dissolved. Dilute with water to about 150mL, boil, remove, and precipitate and filter according to 4.3.3. Scrub the beaker and wash the precipitate 4 to 5 times. Combine the two filtrates and heat and concentrate to about 200ml. Note: For daily analysis, one precipitation separation is sufficient, but iron and manganese should be prevented from filtering through and interfering with the determination. 4.3.5 Add 34 drops of methyl red solution (3.11) to the filtrate, acidify with hydrochloric acid (3.2), add 5 mL more, add 20 mL of ammonium oxalate solution (3.12), boil, remove and add 23 drops of methyl red solution (3.11), slowly add ammonium hydroxide (3.6) until the solution turns star yellow, and add 1-2 mL in excess. Heat to boiling and keep warm at low temperature for 2 hours. 4.3.6 Filter with medium-speed quantitative filter paper and a small amount of quantitative filter paper pulp, wash the beaker and precipitate with ammonium oxalate solution (3.13) 1-2 times, and then wash the beaker and precipitate with warm water 4-5 times until there is no silver oxalate ion (check with silver nitrate solution (3.14), Note: When washing calcium oxalate precipitate, warm water should be used instead of hot water, because calcium oxalate has a high solubility in hot water. The number of washings should not be too many, otherwise the result will be too low: if the silver oxalate ion is not washed clean, the result will be too high. 146
JB/T 9220.7--1999
4.3.7 Place the precipitate together with the filter paper and pulp in the original beaker, add 150mL hot water and 25ml sulfuric acid (3.15), stir to dissolve the precipitate, unfold the filter paper, stick it to the inner wall of the beaker, immediately titrate with potassium permanganate standard solution (3.16) until it turns slightly red, then pour the filter paper into the solution and stir thoroughly, continue titrating until the slightly red color appears and does not disappear for 0.5min, which is the end point. 5 Calculation of analysis results
Calculate the percentage of calcium oxide according to formula (2): (VV.)NX56. 08
mX2000
·Equivalent concentration of potassium permanganate standard solution; where: N
V—volume of potassium permanganate standard solution consumed in titration, mL, V. --volume of potassium permanganate standard solution consumed in blank test, mL; m-sample amount, g:
56.08---molecular weight of calcium oxide.
6 Tolerance
The difference in analysis results between laboratories should not be greater than the tolerance listed in Table 1. When calibrated with standard samples, the deviation shall not exceed 1/2 of the tolerance listed in Table 1.
Calcium oxide content
15. 00 ~ 25. 00
>25.00~35.00
>35. 00~45. 00
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