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GB/T 14849.3-2020 English PDF (GBT14849.3-2020)

GB/T 14849.3-2020 English PDF (GBT14849.3-2020)

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GB/T 14849.3-2020: Methods for chemical analysis of silicon metal -- Part 3: Determination of calcium content

This Part of GB/T 14849 specifies the method for determination of calcium content in silicon metal. This Part is applicable to determination of calcium content in silicon metal. The range for determination is: 0.0050%~0.55%.
GB/T 14849.3-2020
GB
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 77.040.30
H 17
Replacing GB/T 14849.3-2007
Methods for chemical analysis of silicon metal - Part
3: Determination of calcium content
ISSUED ON: MARCH 06, 2020
IMPLEMENTED ON: FEBRUARY 01, 2021
Issued by: State Administration for Market Regulation;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Flame atomic absorption spectrometry ... 5
4 Chlorophosphonazo I spectrophotometry ... 9
5 Quality assurance and control ... 13
6 Test report ... 13
Foreword
GB/T 14849 ?€?Methods for chemical analysis of industrial silicon?€? consists of the following 11 parts:
- Part 1: Determination of iron content;
- Part 2: Determination of aluminum content - Chrome azurol S
spectrophotometric method;
- Part 3: Determination of calcium content;
- Part 4: Determination of elements content Inductively coupled plasma
atomic emission spectrometric method;
- Part 5: Determination of elements content?€?Analysis using an X-ray
fluorescence method;
- Part 6: Determination of carbon-Infrared absorption method;
- Part 7: Determination of phosphorus content - Phosphorus molybdenum
blue spectrophotometry;
- Part 8: Determination of copper content - Atomic absorption spectrometric method;
- Part 9: Determination of titanium content - Diantipyryl methane
spectrophotometry;
- Part 10: Determination of mercury content - Atomic fluorescence
spectrometric method;
- Part 11: Determination of chromium content - Diphenylcarbazide
spectrophotometric method.
This Part is Part 3 of GB/T 14849.
This Part was drafted in accordance with the rules given in GB/T 1.1-2009. This Part replaces GB/T 14849.3-2007 ?€?Methods for chemical analysis of silicon metal - Part 3: Determination of calcium content?€?. Compared with GB/T
14849.3-2007, in addition to editorial modifications, the main technical changes are as follows:
- added warning;
- modified range of determination from 0.020%~0.30% to 0.0050%~0.55%
Methods for chemical analysis of silicon metal -
Part 3: Determination of calcium content
Warning - The personnel using this Part shall have practical experience in formal laboratory work. This Part does not point out all possible
security issues. The user is responsible for taking appropriate safety and health measures and ensuring compliance with the conditions stipulated
by relevant national laws and regulations.
1 Scope
This Part of GB/T 14849 specifies the method for determination of calcium content in silicon metal.
This Part is applicable to determination of calcium content in silicon metal. The range for determination is: 0.0050%~0.55%.
2 Normative references
The following referenced documents are indispensable for the application 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 8170, Rules of rounding off for numerical values & expression and
judgement of limiting values
3 Flame atomic absorption spectrometry
3.1 Method summary
Use hydrofluoric acid and nitric acid to dissolve test material. Perchloric acid smokes to remove silicon and fluorine. Use nitric acid to dissolve the residue. Use lanthanum salt to suppress aluminum interference. At a wavelength of 422.7nm of flame atomic absorption spectrometer, use air-acetylene flame to measure the absorbance of calcium. Calculate the mass fraction of calcium. 3.2 Reagents and materials
Unless otherwise specified, in the analysis, it shall only use the confirmed according to the concentration. The ratio of the absorbance difference of the highest segment to the absorbance difference of the lowest segment
shall not be less than 0.7.
3.3.2 Platinum dish, 100mL.
3.3.3 Teflon beaker, 250mL.
3.4 Specimen
The specimen shall be able to pass through a 0.149mm standard sieve. Use magnet to remove iron.
3.5 Test steps
3.5.1 Test material
Weigh 0.50g of specimen (3.4), to the nearest of 0.0001g.
3.5.2 Number of determinations
Do two tests in parallel.
3.5.3 Blank test
Conduct blank test with test material (3.5.1).
3.5.4 Determination
3.5.4.1 Place test material (3.5.1) in a platinum dish (3.3.2) or a PTFE beaker (3.3.3). Add 10mL of hydrofluoric acid (3.2.2). Add nitric acid (3.2.3) dropwise till test material is decomposed. Add 1mL of perchloric acid (3.2.1). Heat on a low temperature electric furnace until the sample is completely dissolved. Steam to nearly dry. Remove and cool it.
3.5.4.2 Add 5mL of nitric acid (3.2.3). Wash in a little water along the wall of the dish. Heat to completely dissolve the residue. Cool to room temperature. 3.5.4.3 Based on the mass fraction of calcium, pipette corresponding volume (V) of test solution (3.5.4.2) according to Table 1. Place in a 100mL volumetric flask. Add 5mL of lanthanum salt solution (3.2.5). Add nitric acid according to Table 1 (3.2.3). Use water to dilute to the scale. Mix well.
Table 1 -- Volume of pipetted test solution, volume of added nitric acid and dilution factor
Mass fraction
Volume of pipetted test
solution V
mL
Volume of added
nitric acid
mL
Dilution factor
R1
4.2.1 Hydrofluoric acid (??=1.14g/mL).
4.2.2 Nitric acid (1+1).
4.2.3 Perchloric acid (1+1).
4.2.4 Hydrochloric acid (1+1).
4.2.5 Triethanolamine (1+3), stored in polyethylene bottles.
4.2.6 1,10-phenanthroline ethanol solution (4g/L): Weigh 4.0g of 1,10-
phenanthroline (C12H8N2??H2O). Place in a 1000mL volumetric flask. Add ethanol to dissolve. Then use ethanol to dilute to the scale. Mix well.
4.2.7 Acetylacetone (1+40).
4.2.8 Buffer solution: Weigh 21.00g of borax (Na2B4O7??10H2O), 4.00g of sodium hydroxide (guaranteed reagent). Use water to dissolve and dilute to 1000mL. The pH of this solution is 10.5. Store in a polyethylene bottle.
4.2.9 Chlorophosphonazo I (C16H18O14N2S2PCl) solution (1.0g/L).
4.2.10 EGTA-Pb solution (0.02mol/L): Weigh 1.90g of ethylene glycol diethyl ether diamine tetraacetic acid (EGTA). Place in a 250mL beaker. Add about 100mL of water. Heat. Add sodium hydroxide (1mol/L) dropwise to help dissolve. And adjust to neutral. Take another 1.53g of lead chloride. Place in a 250mL beaker. Add about 100mL of water. Heat to dissolve. Mix the two solutions while they are hot. Adjust to neutral. After cooling, use water to dilute to 250mL. Mix well.
4.2.11 Calcium standard stock solution: Weigh 2.4970g of calcium carbonate that has been dried at 105??C and cooled to room temperature in a dryer
(reference reagent, ???99.95%). Place in a beaker. Add about 200mL of
water. Then add hydrochloric acid (4.2.4) dropwise to completely dissolve. Excess by 20mL. Heat to boil to drive off carbon dioxide. Cool. Transfer to a 1000mL volumetric flask. Use water to dilute to the scale. Mix well. 1mL of this solution contains 1mg of calcium.
4.2.12 Calcium standard solution: Pipette 10.00mL of calcium standard stock solution (4.2.11) into a 1000mL volumetric flask. Use water to dilute to the scale. Mix well. 1mL of this solution contains 10??g of calcium.
4.3 Instruments
4.3.1 Spectrophotometer.
4.3.2 Platinum dish, 100mL.
4.5.4.4 Pipette the test solution (4.5.4.3) into a 50mL volumetric flask according to Table 4. Add 6.0mL of triethanolamine (4.2.5), 4.0mL of 1,10-phenanthroline ethanol solution (4.2.6), 3.0mL of acetylacetone (4.2.7), 10.0mL of buffer solution (4.2.8), 5.00mL of azo chlorophosphine I solution (4.2.9). Each reagent needs to be mixed well when it is added. Use water to dilute to the scale. Mix well. Leave it for 5min.
4.5.4.5 Move part of the color developing solution (4.5.4.4) into the cuvette (4.3.4). In the remaining solution, add 3~5 drops of EGTA-Pb solution (4.2.10). Shake well until the color fades completely. Use this faded solution as a reference. At a wavelength of 580nm of spectrophotometer, measure its
absorbance. Subtract the absorbance of the blank test solution (4.5.3). Find the mass of calcium from the working curve (m3).
4.5.5 Drawing of working curve
4.5.5.1 Pipette 0mL, 0.50mL, 1.00mL, 2.00mL, 3.00mL, 4.00mL, 5.00mL,
6.00mL of calcium standard solution (4.2.12) to respectively place in a set of 50mL volumetric flasks. The following shall be carried out according to 4.5.4.4~4.5.4.5.
4.5.5.2 Take the mass of calcium in the series of standard solutions as the abscissa, the corresponding absorbance minus the absorbance of the "zero" concentration solution in the series of standard solutions as the ordinate, to draw the working curve.
4.6 Processing of test data
Calculate the mass fraction of calcium wCa according to formula (2):
Where,
m3 - Mass of calcium in the test solution found from the working curve, in micrograms (??g);
m2 - Mass of test material, in grams (g);
R2 - Dilution factor.
The test result retains two significant digits. Numerical rounding is carried out in accordance with the provisions of GB/T 8170.
4.7 Precision

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