Ferromanganese，ferromanganese-silicon，nitrogen-bearing ferromanganese and manganese metal—Determination of manganese content—Potentiometric method， titrimetric method after ammonium nitrate oxidation and titrimetric method after perchloric acid oxidation
Ferromanganese, ferromanganese-silicon, nitrogen-bearing ferromanganese and manganese metal - Determination of manganese content - Potentiometric method, titrimetric method after ammonium nitrate oxidation and titrimetric method after perchloric acid oxidation
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1 Scope
This document describes the methods for determination of manganese content in ferromanganese, ferromanganese-silicon, nitrogen-bearing ferromanganese and manganese metal using the potentiometric method, titrimetric method after ammonium nitrate oxidation and titrimetric method after perchloric acid oxidation.
This document is applicable to the determination of the manganese content in ferromanganese, ferromanganese-silicon, nitrogen-bearing ferromanganese and manganese metal. The determination range (mass fraction) is 50.00%~98.00%. Method I is not applicable to the determination of manganese content in ferromanganese, ferromanganese-silicon, nitrogen-bearing ferromanganese and manganese metal with chromium and vanadium content (mass fraction) greater than 0.4%.
2 Normative references
The following documents contain provisions which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 4010 Ferroalloys sampling and preparation of samples for chemical analysis
GB/T 6379.1 Accuracy (trueness and precision) of measurement methods and results - Part 1: General principles and definitions
GB/T 6379.2 Accuracy (trueness and precision) of measurement methods and results - Part 2: Basic method for the determination of repeatability and reproducibility of a standard measurement method
GB/T 6682 Water for analytical laboratory use - Specification and test methods
GB/T 8170 Rules of rounding off for numerical values & expression and judgment of limiting values
GB/T 12806 Laboratory glassware - One-mark volumetric flasks
GB/T 12807 Laboratory glassware - Graduated pipettes
GB/T 12808 Laboratory glassware - One-mark pipettes
3 Terms and definitions
No terms and definitions are listed in this document.
4 Method I: Potentiometric method
4.1 Principle
The samples are decomposed by hydrochloric acid, nitric acid, perchloric acid and hydrofluoric acid, and the manganese content is determined by potentiometric titration with potassium permanganate standard solution in neutral potassium pyrophosphate medium. Manganese (II) ions are oxidized and permanganate ions are reduced to form manganese (III) pyrophosphate complex. The stoichiometric ratio of manganese (II) ions to permanganate ions is 4:1.
4.2 Reagents and materials
Unless otherwise specified, only recognized analytically pure reagents and distilled water or deionized water of Grade III and above specified in GB/T 6682 or water with equivalent purity shall be used.
4.2.1 Perchloric acid, ρ=1.67g/mL.
4.2.2 Hydrofluoric acid, ρ=1.15g/mL.
4.2.3 Nitric acid, ρ=1.42g/mL.
4.2.4 Hydrochloric acid, ρ=1.19g/mL.
4.2.5 Sulfuric acid, ρ=1.84g/mL.
4.2.6 Hydrochloric acid, 1+2.
4.2.7 Hydrochloric acid, 1+4.
4.2.8 Sulfuric acid, 1+1.
4.2.9 Sodium carbonate solution, 50g/L. Weigh 5g of anhydrous sodium carbonate (Na2CO3), dissolve it in 60mL of water and dilute to 100mL with water. Transfer the resultant solution into a reagent bottle.
4.2.10 Potassium pyrophosphate solution, 120g/L. Weigh 120g of potassium pyrophosphate (K4P2O7·3H2O), dissolve it in 1,000mL of water in a 2,000mL beaker and transfer the resultant solution to a brown reagent bottle for storage.
4.2.11 Potassium permanganate, recrystallized. Weigh 50g of potassium permanganate (of a purity not less than 99.5%) into a 500mL conical flask (see 4.3.1) with a grinding mouth, and add 200mL of hot water to dissolve it. Connect the conical flask (see 4.3.1) with a reflux condenser (see 4.3.2), boil the solution for 20min, and conduct rapid vacuum filtration of the hot solution in a sand core crucible G3 or G4 (see 4.3.3). Place the filtered solution quickly in an ice water bath and cool it to 10℃, allowing the crystalline precipitate to settle. Slowly pour out the upper clarification solution, transfer the crystals to another sand-core crucible G3 or G4 (see 4.3.3) with a glass scraper, and filter them on a suction filter for 5min to remove most of the mother liquid.
Dissolve the crystals in a 160mL distilled water (ion exchange water not allowed) and recrystallized again.
Suck and filter the recrystallized potassium permanganate for 5min, and transfer the crystals to a glass dish or porcelain dish with a diameter of 150mm by a glass scraper, air-dry them in a dust-proof environment away from light. Grind the crystals with a glass scraper until they are no longer lumped, and dry them at 110℃±5℃ for 2h~3h. Then put them in a brown weighing bottle with a ground glass stopper and keep it away from light.
The manganese content (mass fraction) of potassium permanganate obtained by recrystallization is 34.76%.
4.2.12 Manganese standard solution, 1.00mg/mL. Weigh 10g of electrolytic manganese (flake, with a purity greater than 99.95%) into a 400mL or 500mL beaker, add 50mL of water and 5mL of nitric acid (see 4.2.3), let the mixture stand for several minutes and then remove the oxide layer on the surface until the manganese surface brightens. Rinse it with water for 6 times, then wash it with acetone, and dry it at 100℃ for 10min.
Quickly weigh 1.0000g of treated electrolytic manganese into a 400mL or 500mL beaker, and add 20mL of sulfuric acid (see 4.2.8) and about 100mL of water. Boil the solution until it is clear, cool it down and transfer it into a 1,000mL volumetric flask. Then dilute it to the scale with water and shake well.
This solution contains 1.00mg of manganese per mL.
Note: If the weighing cannot accurate to 1.0000g, the manganese content of the solution can be calculated based on the mass of electrolytic manganese actually weighed.
4.2.13 Potassium permanganate standard titration solution: c (1/5 KMnO4)≈0.05mol/L. Weigh 1.6g of potassium permanganate, put it in a 2,000mL conical flask, slowly heat and boil it with 1,000mL of water until it dissolves. Then cool it, put it in the dark for 6d, filter it with a glass wool or sand-core crucible G3 or G4, and keep the filtrate in a brown glass flask.
Calibrate the potassium permanganate standard titration solution by the following two methods:
a) Calibrate with manganese standard solution (see 4.2.12). Pipette 100.00mL of manganese standard solution (see 4.2.12) in a 500mL~800mL beaker, add 150mL of potassium pyrophosphate solution (see 4.2.10) while stirring. Place the beaker on an electromagnetic stirrer (see 4.3.6), place stirring rotors (see 4.3.7) in the beaker, and start the electromagnetic stirrer. Add hydrochloric acid (see 4.2.7) or sodium carbonate solution (see 4.2.9) dropwise to adjust the pH value of the solution to 7.00±0.02, and measure the pH value with an acidometer (see 4.3.5). Titrate with the potassium permanganate standard titration solution on a potentiometric titrator (see 4.3.4) until obvious potential jump or pointer deflection occurs.
Carry out blank determination along with calibration.
Calculate the mass concentration ρ1 of manganese corresponding to potassium permanganate standard titration solution using Formula (1), expressed in g/mL.
Foreword I
Introduction III
1 Scope
2 Normative references
3 Terms and definitions
4 Method I: Potentiometric method
5 Method II: Titrimetric method after ammonium nitrate oxidation
6 Method III: Titrimetric method after perchloric acid oxidation
7 Test report
Annex A (Normative) Flow chart of procedure for acceptance of sample analysis results
Annex B (Informative) Additional information for common precision tests
