This standard specifies the determination of phosphorus content by phosphomolybdenum blue spectrophotometry. This standard is applicable to the determination of phosphorus content in silicon calcium alloys, and the determination range is: ≤0.06%. GB/T 4700.4-1998 Chemical analysis method for silicon calcium alloys Phosphomolybdenum blue spectrophotometric determination of phosphorus content GB/T4700.4-1998 Standard download decompression password: www.bzxz.net

GB/T 4700.4—1998
This standard is equivalent to Chapter 6 “Determination of phosphorus content by molybdenum blue photometric method” in JIS G1324-1989 “Chemical analysis method for silicon calcium alloy” in terms of technical content. Www.bzxZ.net
This revision deletes Chapter 3 Instrument, spectrophotometer in the original GB/T4700.4-1984. Some modifications are made in the analysis steps: the sample weight is changed from 0.5000g to 1.0000g; the amount of the aliquot is changed from 25mL to 100ml and 10ml to 25mL; the color developing solution is changed from 25mL to 20mL; heating in boiling water for 15min is changed to 10min. This standard replaces GB/T4700.4—1984 “Chemical analysis method for silicon calcium alloy-determination of phosphorus content by molybdenum blue photometric method” from the date of implementation.
This standard was proposed by the former Ministry of Metallurgical Industry.
This standard is under the jurisdiction of the Information Standards Institute of the Ministry of Metallurgy. The drafting units of this standard are: Beijing Shougang Alloy Plant, Information Standards Institute of the Ministry of Metallurgy. The main drafters of this standard are: Chen Yuan, Li Simao, Zhao Xinlian, Zhan Zhaoxiang, Chen Zibin. This standard was first issued in October 1984. 152
1 Scope
National Standard of the People's Republic of China
Chemical analysis method of calcium-silicon alloy
Determination of phosphorus content by phasphomolybdenum blue spectrophotometry
Methods for chemical analysis of calcium-silicon -The phasphomolybdenum blue photometric method forthe determination of phosphorus content This standard specifies the determination of phosphorus content by phasphomolybdenum blue spectrophotometry. This standard is applicable to the determination of phosphorus content in calcium-silicon alloy, and the determination range is: ≤0.06%. 2 Method Summary
GB/T 4700.4--1998
Replaces GB/T4700.41984
The sample is dissolved in nitric acid and hydrofluoric acid, and perchloric acid is fuming to oxidize phosphorus to orthophosphoric acid. Sodium bisulfite is used to reduce iron, and ammonium molybdate and hydrazine sulfate are added to react to generate phosphomolybdenum blue. The absorbance is measured at a wavelength of 825nm on a spectrophotometer. 3 Reagents
3.1 Nitric acid (1+1).
3.2 Hydrofluoric acid (pl.15g/mL).
3.3 Perchloric acid (pl.67g/mL).
3.4 ​​Sodium bisulfite solution (100g/L). 3.5 Color developer solution
3.5.1 Ammonium molybdate solution: Weigh 20g ammonium molybdate [(NH,).Mo,O24*4H,O], heat and dissolve in 300mL water, add 650mL sulfuric acid (1+1), cool, transfer to a 1000mL volumetric flask, dilute to scale, and mix. 3.5.2 Hydrazine sulfate solution: Weigh 1.5g hydrazine sulfate, place in a 200mL beaker, add water to dissolve, transfer to a 1000mL volumetric flask, dilute to scale, and mix.
3.5.3 When using, take 25ml. ammonium molybdate solution (3.5.1), 10ml hydrazine sulfate solution (3.5.2) and 65ml water and place in a 150mL beaker and mix.
3.6 Phosphorus standard solution: Weigh 0.4394g of potassium dihydrogen phosphate (reference reagent) which has been dried to constant weight at 105-110°C and cooled to room temperature in a desiccator, place in a 200mL beaker, dissolve in water, transfer to a 1000mL volumetric flask, dilute to scale, and mix. This solution contains 100μg of phosphorus in 1mL.
4 Sample
The sample should pass through a 0.125mm sieve.
5 Analysis steps
5.1 Sample quantity
Approved by the State Administration of Quality and Technical Supervision on December 7, 1998 and implemented on July 1, 1999
Weigh 1.0000g of sample.
5.2 Blank test
Carry out a blank test with the sample.
5.3 Determination
GB/T4700.4—1998
5.3.1 Place the sample (5.1) in 100mL platinum III (or a 200mL polytetrafluoroethylene beaker), add 20mL nitric acid (3.1), add 5mL hydrofluoric acid (3.2) dropwise until the sample is completely dissolved. When the reaction is intense, dissolve while cooling with water, add 10mL perfluoric acid (3.3), heat until perchloric acid smoke appears for 1min, remove, transfer to a 200mL beaker with warm water, cover with a watch glass, continue heating and evaporating until perchloric acid smoke appears, reflux for 1min, and place to cool.
5.3.2 Add about 30mL of warm water to dissolve soluble salts. Rinse the watch glass III, and filter the test solution into a 100ml volumetric flask, wash the beaker and precipitate with warm water 4 to 5 times, dilute to the scale with water after cooling, and mix well. 5.3.3 Pipette 10.00mL of solution (5.3.2) into a 100mL volumetric flask, add 10mL of sodium bisulfite solution, and heat in boiling water for 10min. After cooling to room temperature, dilute with water to the mark and mix. 5.3.4 Pipette part of solution (5.3.3) into an appropriate absorbent dish, and measure its absorbance at a wavelength of 825nm using the blank solution accompanying the sample as a reference on a spectrophotometer.
5.4 Drawing of working curve
5.4.1 Pipette 0, 1.00, 3.00, 5.00, 7.00, and 9.00mL of phosphorus standard solution (3.6), respectively, into a group of 200mL beakers, add 5mL of perchloric acid (3.3), cover with table blood, heat until perchloric acid smoke appears, remove and cool, and then operate according to 5.3.2 and 5.3.3. 5.4.2 Transfer part of the solution (5.4.1) to an appropriate colorimetric medium III, use the reagent blank as a reference, measure its absorbance at a wavelength of 825 nm on a spectrophotometer, and plot a working curve with the phosphorus content as the horizontal axis and the absorbance as the vertical axis. 6 Calculation of analysis results
Calculate the percentage of phosphorus according to the following formula:
P(%) =
Where: mi--phosphorus content obtained from the curve·g; one sample amount·g
one test wavelength ratio.
7 Allowable difference
The difference in analysis results between laboratories should not be greater than the allowable difference specified in Table 1. Table 1 Allowable difference
0.010~0.030
≥0. 030~0.060
Allowable difference
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