This standard specifies the EDTA titration method for the determination of calcium content. This standard is applicable to the determination of calcium content in silicon-calcium alloys, with a determination range of 20.00% to 36.00%. GB/T 4700.2-1988 Chemical analysis method for silicon-calcium alloys Determination of calcium content by EDTA titration GB/T4700.2-1988 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Chemical analysis method of celcium silican
EDTA titrimetric method for the determination of calcium content
Methods for chemlcal onalysis af celcium silicanThe RDTA titrimetric method for the determination of calcium content1Subject content and scope of application
This standard specifies the EDTA titrimetric method for the determination of calcium content. This standard is applicable to the determination of calcium content in residual calcium alloys, with a determination range of 20.00% to 36.00%. 2 Method Summary
Jc 669. 782. 5'891
:543.244.6
GB4700.2—88
Substitute GB t71. 2—81
The sample is dissolved with nitric acid and hydrofluoric acid, fluoride ions are removed by bubbling with perchloric acid, decomposed with hydrochloric acid, neutralized with ammonium hydroxide and filtered to separate impurities such as iron. Then, when the pH is not less than 12, add calcium indicator and titrate with EDTA standard solution. According to the consumption base of EDTA standard solution, calculate the percentage of calcium.
3 Reagents
3-1 Ammonium chloride.
3. 2 Hydrofluoric acid (p 1. 15 g/mL),
3.3 Perchloric acid (p 1.67 g/mL).
3.4 ​​Nitric acid (1+1).
3. 5 Hydrochloric acid (2+1)
3. 6 Hydrochloric acid (1+10)
3.7 Ammonium hydroxide (1-1).
3.8 Ammonium chloride solution: 20 g/L.
3.9 Potassium hydroxide solution: 0. 45 g/mL.
3.10 Hydroxylamine hydrochloride solution; 60 mg/mL.
3. 11 Hydroxygen hydroxide solution; 1 g/ml. 3.12 Magnesium hydroxide emulsion: Weigh 5 g magnesium chloride (MgCl26Hz0). Dissolve in 240 mL water, add 10 mL sodium hydroxide (0. 2 ε/mL), shake vigorously to make it milky. 3.13 Methyl red solution: Weigh 0.2 g methyl red and dissolve in 90 tnL ethanol, dilute to 100 mL with water, and mix well. 3.14 Calcium indicator: weigh 0.2 g of calcium indicator 2-hydroxy-1-(2-hydroxy-4-sulfo-1-yl azo)-3-hydroxycarboxylic acid sodium salt, add 20 g of sulfuric acid, grind thoroughly in a mortar, and mix. 3.15 Chrome black T solution: weigh 1.2 g of Chrome black T (C2mH,O,N,SNa), add 15 mL of triethanolamine, add 5 mL of ethanol, and mix. 3.16 Nitrogen chloride buffer solution: weigh 67.5 g of ammonium fluoride in water, add 570 mL of sodium hydroxide (p0.9 g/mL), dilute to 1000 mL with water, and mix. This solution is H 10. Approved by the Ministry of Metallurgical Industry of the People's Republic of China on September 8, 1988 and implemented on January 1, 1990
GE 470 0. 2— 88
3.17 Zinc standard solution: c(Zn3+)=0.01000mol/L, weighing 0.3269B pure zinc (99.99%) [If the zinc surface has been oxidized, it can be washed with hydrochloric acid (1+1), water, and acetone in sequence, and then dried at 110°C for 6 minutes and then rinsed with 1, add about 50mL of water, 20mL of hydrochloric acid (3.5), 5 drops of bromine water, heat to dissolve + boil to remove bromine, cool and pour into a 500mL container flask, dilute to the scale with water, and add 1. 3.18 EDTA standard solution: c(CuH:N,O.Naz-2Ha0)=0.01tmol/L3. 18.1 PreparationbzxZ.net
Weigh 3,722% ethylenediaminetetraacetic acid disodium solution in water, transfer to a 1000mL volumetric flask, dilute to scale with water, and mix. 3.18.2 Calibration
Pipette 25.00mL zinc standard solution (3.17), add about 75mL water, and mix with sodium hydroxide solution (3.11) until it is slightly alkaline, then add 2mL ammoniacal ammonium nitride buffer solution (3.16) and mix. Add 3 drops of chrome black T solution (3.15), the solution is wine red, and add EDTA standard solution (3,t8.1) until the solution is bright blue. Calculate the concentration of EDTA standard solution according to formula (1): XV
Concentration of EDTA standard solution after calibration, mol/L;:
r—Concentration of zinc standard solution (3.17), mal/L;-—Volume of zinc standard solution (8.17) transferred, mL: —Volume of EDTA standard solution consumed during titration, mL. 4 Sample
The sample should pass through a 0.125 mm sieve.
5 Analysis steps
5.1 Sample volume
Weigh 0.200 0 sample.
5. 2 Empty self-test
Carry out empty self-test with the sample.
5.3 Determination
(1)
5.3.1 Place the sample (5.1) in platinum blood, add 10 mL nitric acid (3.4), and add about 5 mL hydrochloric acid (3.2). Cool with water while decomposing. After the violent reaction stops, add 10 ml of perchloric acid (3.3) and evaporate until white perchloric acid smoke appears. Take out the platinum blood, rinse the sub-wall with water, and evaporate again until white pernitrogen smoke appears. Concentrate its volume to about 3 mL: 5.3.2 Take out the platinum blood and cool it. Add 30 mL of warm hydrochloric acid (3.6) to dissolve the soluble salts. Transfer it to a 300 mL beaker, add 2 g of ammonium chloride (3.1) and a few drops of methyl red solution (3.13), and slowly add ammonium hydroxide (3.7) while stirring until the solution turns yellow. Heat and boil for 5 minutes, then filter with quantitative filter paper. The filtrate is placed in a 300 mL beaker as the main liquid. Wash the precipitate on the filter paper several times with a small amount of warm hydrochloric acid (3.6), then wash it with warm water, and heat to dissolve the precipitate. Add a few drops of neutral red solution (3.13), and use the same method as above to form a precipitate, then filter, wash with warm ammonium solution (3.8) 5 to 6 times, and discard the precipitate. Filter the washings and transfer to a 250 mL volumetric flask in a soil solution, dilute to the mark with water, and mix.
5.3.3 Transfer 25.00mL of solution (5.3.2) to a 300mL conical flask, dilute with water to about 50mL, add 4mL of potassium hydroxide solution (3.9), mix by shaking the teeth and let stand for 3-4min, add 5mL of hydroxylamine hydrochloride solution (3.10) and 0.1g of calcium indicator (3.14) and titrate with EDTA standard solution (3.18.2). When the solution starts to turn from purple-red to blue, add 4ml of magnesium hydroxide emulsion (3.12) and continue titrating until the solution turns pure blue.
Calculation of analysis results
Calculate the percentage of calcium using formula (2):
GR 47 0 0: 2 88
Ca(%) - (V+ Fa) - c, × 0. 01008× 100
Where: V——The volume of EDTA standard solution consumed in titration test, mL; VA The volume of EDTA standard solution consumed in blank test, mL. Concentration of FDTA standard solution after calibration mol/L
Sample volume+8:
---Test solution fractionation ratio:
**+(2)
0.04008——1.00 mL EDTA standard solution [c(C:H,N,0,Na2*2H;0)= 1.000 mol/L] is equivalent to the mass of calcium, B. Jiang: The analysis result is expressed to the decimal place. Allowable difference
The difference in analysis results between laboratories should not be greater than the allowable difference calcium listed in the table
20.0F-25.00
>25.00~36. 00
Additional Notes:
This standard was drafted by the Ferroalloy Plant of Capital Iron and Steel Company. This standard has the following levels: GB 4700,2-88 T
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