JB/T 7948.3-1999 JB/T 7948.3-1999 Chemical analysis method for melting flux - Determination of manganese oxide content by permanganate photometric method JB/T7948.3-1999 Standard download decompression password: www.bzxz.net

JB/T7948.3--1999
This standard is equivalent to adopting "OCT22978.1~22978.10--78 "Chemical Analysis Method for Baked Flux". The revision of the determination of manganese oxide content by permanganate photometry. This standard is an editorial revision of JB/T7948.3--95 Chemical Analysis Method for Melting Flux, and its technical content has not changed. This standard replaces JB/T7948.3--95 from the date of implementation. This standard is proposed and managed by the National Welding Standardization Technical Committee. The drafting unit of this standard: Harbin Welding Research Institute. The main drafters of this standard: Lin Kegong and Bai Shu. 356
1 Scope
Standard of the Machinery Industry of the People's Republic of China
Methods for chemical analysis of melted welding fluxesThe permanganate photometric method fordetermination of manganese oxide contentJB/T7948.3-1999
Replaces JB/T 7948. 3-95
This standard is applicable to the determination of manganese oxide content in melted welding fluxes. The determination range is 0.50% to 10.0%. This standard complies with GB/T1467-1978 "General Principles and General Provisions for Chemical Analysis Methods for Metallurgical Products". 2'Cited Standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard was published, the versions shown were valid. All standards are subject to revision. Parties using this standard should explore the possibility of using the latest version of the following standards. GB/T1467--1978 General Principles and General Provisions for Chemical Analysis Methods of Metallurgical Products JB/T7948.2--1999 Chemical Analysis Methods for Melting Flux Potentiometric Titration for Determination of Manganese Oxide Content 3 Method Summary
This method is based on the oxidation of divalent manganese ions to heptavalent ions in an acidic medium with silver nitrate as a catalyst and ammonium persulfate, and the absorbance is measured at a wavelength of 520-530nm by a spectrophotometer. The percentage of manganese oxide is thus determined. 4 Reagents
4.1 Nitric acid (specific gravity 1.42).
4.2 Nitric acid (specific gravity 1.84).
4.3 Phosphoric acid (specific gravity 1.70).
4.4 Sulfuric acid-phosphoric acid mixture: Slowly pour 200ml of sulfuric acid (4.2) into 750ml of water and cool. Add 50ml phosphoric acid (4.3). 4.5 Silver nitrate solution (1%), stored in a brown bottle. 4.6 Ammonium persulfate solution (15%).
4.7 Manganese standard solution: According to the steps in 4.16 of JB/T7948.2-1999, transfer 10ml manganese standard solution to a 150ml conical cup, add 25ml sulfuric acid-phosphoric acid mixture (4.4), heat and evaporate until bone white smoke, remove and cool slightly. Add 30ml water, mix well, and cool to room temperature. Transfer to a 500ml volumetric flask, dilute to scale with water, and mix well. This solution contains 0.02mg manganese in 1ml. 5 Instruments
Spectrophotometer.
Approved by the National Bureau of Machinery Industry on June 24, 1999
Sold and implemented on January 1, 2000www.bzxz.net
6 Sample
JB/T7948.3-1999
The sample should pass through a 200-mesh screen. Pre-dry at 105-110℃ for 1 hour, 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 quantity
Weigh 0.5000g of sample and transfer 50.00ml of test solution according to steps 7.3.1 to 7.3.5 of JB/T7948.2-1999. 7.3 Determination
7.3.1 Place the test solution (7.2) in a 300mL beaker, add 5mL nitric acid (4.1) and 10mL sulfuric acid (4.2), cover with a watch glass, heat and evaporate until white smoke appears, and cool slightly. Rinse the watch glass and beaker with water, evaporate again until white smoke appears, and cool. Add a small amount of water, mix. Cool to room temperature. Pour into a 250mL volumetric flask, dilute with water to the mark, and mix. 7.3.2 Transfer 10.00mL of solution (7.3.1) to a 100mL volumetric flask, add 10mL water and 10mL silver nitrate solution (4.5) and 20mL ammonium persulfate solution (4.6), heat to boiling, remove and cool to room temperature. Dilute with water to the mark, mix. Let stand for 20min. 7.3.3 Transfer part of the solution (7.3.2) to a 3 cm cuvette and measure its absorbance at a wavelength of 520-530 mm using water as a reference. Find the corresponding amount of manganese from the working curve. 4: Drawing of working curve
7. 4. 1 Transfer 1: 00 mL, 2. 00 mL 4. 00 mL; 6. 00 mL; 8. 00 mL; 10. 00 mL; 12. 00 ml. 14. 00 mL; 16.00 mL of manganese standard solution (4.7) to a group of 100 mL volumetric flasks respectively and operate according to steps 7.3.2-7.3.3. Draw a working curve with the amount of manganese as the horizontal axis and the absorbance as the vertical axis. 8 Calculation of analysis results
Calculate the percentage of manganese oxide by (): m×1.291×100%
Where: m——the amount of manganese found from the working curve, g: 1.291—the conversion factor for manganese oxide; mo
9 Allowable difference
Pipette the amount of test solution (7.3.2) equivalent to the sample.g. The difference between the parallel determination results should not be greater than the allowable difference listed in Table 1. Table 1 Allowable difference
Amount of manganese oxide
0.50~1.00
>1.00~2.00
>2.00～ 5.00
>5.0010.00
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