JB/T 7948.8-1999 This standard is equivalent to ΓOCT 2978.1~.10-78 "Methods for chemical analysis of melting flux". This standard is a revision of JB/7948.8-95 "Methods for chemical analysis of melting flux - Determination of phosphorus content by molybdenum blue photometry". During the revision, only editorial changes were made according to relevant regulations, and its technical content has not changed. This standard is applicable to the determination of phosphorus content in melting flux, with a determination range of 0.010%~0.20%. This standard was first issued in 1985 as GB 5292.8-85 and was adjusted to JB/T 7948.8-95 in April 1996. JB/T 7948.8-1999 Methods for chemical analysis of melting flux - Determination of phosphorus content by molybdenum blue photometry JB/T7948.8-1999 Standard download decompression password: www.bzxz.net

JB/T7948.8—1999
This standard is equivalent to "OCT22978.1~22978.10—78 Chemical Analysis Method for Melting Flux". This standard is an editorial revision of JB/T7948.8--95 "Chemical Analysis Method for Melting Flux", and its technical content has not changed. This standard replaces JB/T7948.8—95 from the date of implementation. The closing section A of this standard is the appendix of the standard.
This standard is proposed and managed by the National Technical Committee for Welding Standardization. The drafting unit of this standard: Harbin Welding Research Institute. The main drafters of this standard: Lin Kegong, Bai Chedu. 376
Determination of Phosphorus by Molybdenum Blue Photometric Method" Revision. Only 1 Scope
Standard of the Machinery Industry of the People's Republic of China
Methods for chemical analysis of melted welding fluxesThe \molybdenum hlue\ photometric method fordetermination of phosphorus contentThis standard applies to the determination of phosphorus content in melted welding fluxes. Determination range: 0.010%~0.20%. JB/T7948.8--1999
Replaces JB/T 7948.8-95
This standard complies with GB/T1467-1978 "General Principles and General Provisions of Standards for Chemical Analysis Methods of Metallurgical Products". 2 Referenced Standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard is published, the versions shown are valid. All standards will be revised, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T1467-1978 General Principles and General Provisions of Chemical Analysis Methods for Metallurgical Products JB/T7948.2-1999 Chemical Analysis Methods for Melting Flux Potentiometric Titration Method for Determination of Manganese Oxide Content 3 Method Summary
This method is based on the formation of phosphorus-molybdenum complex, which is reduced to phosphorus-molybdenum blue by using divalent iron ions reduced by hydroxylamine hydrochloride in a salt dispersion medium. The percentage of phosphorus is measured by this.
4 Reagents
4.1 Nitric acid (specific gravity 1.42).
4.2 Sulfuric acid (specific gravity 1.84).
4.3 Hydrochloric acid (specific gravity 1.19).
4.4 Hydrochloric acid: Take 312mL of hydrochloric acid (4.3) and dilute it to 1000mL with water (specific gravity about 1.055). 4.5 Ammonium hydroxide (1 + 1).
4.6 Ferric nitrate solution: Weigh 50g of ferric nitrate [Fe(NO):·9H20] and dissolve it in 100ml of water, add a few drops of nitric acid (4.1), and filter. 4.7 Ammonium molybdate solution (5%). Filter.
4.8 Hydroxylamine hydrochloride solution (10%). Prepare when needed and filter. 4.9 Potassium peroxide solution (0.5%).
4.10 Phosphorus standard solution: Weigh 0.4394g of potassium dihydrogen phosphate (reference reagent) baked to constant weight at 105~110C and dissolve it in appropriate amount of water, transfer it to a 1000mL volumetric flask, dilute it to the mark with water, and mix it. This solution contains 0.1mg phosphorus in 1mL. 4.11 Phosphorus standard solution: Transfer 10.00mL of phosphorus standard solution (4.10) to a 100mL volumetric flask, dilute it to the mark with water, and mix it. This solution contains 0.01mg phosphorus in 1mL.
Approved by the State Bureau of Machinery Industry in 1999-0624
Sold from 2000-01-01
5 Instrument
Spectrophotometer.
6 Sample
JB/T7948.8—1999
The sample should pass through a 200-mesh screen. Pre-dry at 105~~110℃ for 1h, and place in a desiccator to cool to room temperature. 7 Analysis Steps
7. 1 Determination Quantity
Three samples should be weighed for determination during analysis, and the average value should be taken. 7.2 Sample volume
Weigh the sample according to Table 1:
Table 1 Sample volume
0. 01~0.10
20. 10~0. 20
7.3 Determination
Weigh the sample
7.3.1 Place the sample (7.2) in a 100mL conical cup, add 20mL hydrochloric acid (4.3), cover with blood, heat at low temperature for 30min: add 2mL nitric acid (4.1), boil to remove nitrogen oxides, cool. Add 15~20mL water, transfer to a 100mL volumetric flask, dilute to the mark with water, mix. Dry filter.
7.3.2 Transfer 20.00mL of solution (7.3.1) to a 50mL volumetric flask, add 2mL of ferric nitrate solution (4.6), neutralize the solution with ammonium hydroxide (4.5) until a stable hydroxide precipitate appears, add hydrochloric acid (4.4) dropwise and shake until the precipitate is dissolved. Add 4mL of hydroxylamine hydrochloride solution (4.8), heat to boiling [the solution should be colorless. If it is yellow, add 23 drops of ammonium hydroxide (4.5). If the solution is turbid, add 12 drops of hydrochloric acid (4.4) to clarify the solution. Cool, add 7mL of hydrochloric acid (4.4), add 4mL of ammonium molybdate solution (4.7) while shaking continuously, and continue shaking for 1~~2min until a cyan blue color appears. Dilute to the mark with water and mix well. Let stand for 5~10min. 7.3.3 Place part of the solution (7.3.2) in a 3 cm cuvette and measure its absorbance at a wavelength of 680 nm using the reagent blank as a reference. Find the corresponding phosphorus content from the working curve. 7.4 Drawing of the working curve
Pipette 1.00 mL; 2.00 mL 3.00 ml.; 4.00 mL; 5.00 mL; 6.00 mL; 7.00 mL+8.00 mL 9.00 mL; 10.00 mL of phosphorus standard solution (4.11) and place them in a group of 50 mL volumetric flasks respectively. Follow the steps of 7.3.2 to 7.3.3. Draw the working curve with phosphorus content as the horizontal axis and absorbance as the vertical axis. 8 Calculation of analysis results
Calculate the percentage of phosphorus according to formula (1):
Where: m
9 Allowable difference
The amount of phosphorus found on the working curve, name
-the amount of test solution (7.3.2) equivalent to the sample name. X100%
The difference between the parallel determination results should not be greater than the allowable difference listed in Table 2: 378
(1)
0. 010～ 0. 020
≥0. 020～0. 040
>0. 040-0. 10
>0. 10～ 0. 20
JB/T 7948.8-1999
Allowance
JB/T7948.8—1999bzxZ.net
Appendix A
(Appendix to the standard)
Alkali fusion method
The determination of phosphorus can also be carried out by alkali fusion of the sample and analysis according to the following method: Weigh the sample according to the provisions in Table 1 (according to the steps 7.3.1~7.3.5 of JB/T7948.2--1999) Transfer 50.00 or 25.00ml of the test solution into a 100mL flask, add 10ml of potassium permanganate solution (4.9), heat, evaporate the solution volume to 5~~8mL, and cool. Filter into a 50mL volumetric flask, wash the filter paper several times with a small amount of water, and the solution volume is about 20mL. Then follow the steps 7.3.2~7.3.3. 380
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