This standard specifies the determination method of bismuth in silver zinc oxide electrical contact materials. This standard is applicable to the determination method of bismuth in silver zinc oxide electrical contact materials. Determination range: 0.05% to 0.50%. JB/T 7774.3-1995 Chemical analysis method for silver zinc oxide electrical contact materials JB/T7774.3-1995 Standard download decompression password: www.bzxz.net

Mechanical Industry Standard of the People's Republic of China
Chemical analysis method of silver zinc oxide electric contact material Thiourea spectrophotometric method for determination of bismuth content
1 Subject content and scope of application
This standard specifies the determination method of bismuth content in silver zinc oxide electric contact material. JB/T7774.3—1995
This standard is applicable to the determination of bismuth content in silver zinc oxide electric contact material. Determination range: 0.05%~0.50%. 2 Reference standards
GB7729—87
General rules for spectrophotometric method for chemical analysis of metallurgical products JB4107.1-85
General rules and general provisions for chemical analysis methods of electric contact materials 3 Principle of the method
The sample is dissolved in nitric acid, and bismuth [] forms a yellow soluble complex with thiourea in an acidic medium for photometric determination. 4 Reagents
4.1 Nitric acid (1+2).
4.2 Nitric acid (1+14).
4.3 Sodium chloride solution (50g/1).
4.4 Thiourea solution (100g/1) (prepare on the same day and filter before use). 4.5 Bismuth standard solution: weigh 0.2310g bismuth nitrate [Bi(NO,)·5H,O] into a 1000ml volumetric flask, add nitric acid (4.2) to dissolve and dilute to scale. Mix well. This solution contains 0.1mg bismuth in 1ml. 5 Instruments
Spectrophotometer.
6 Analysis stepsWww.bzxZ.net
6.1 Sample
Weigh about 0.2g of sample, accurate to 0.0001g. 6.2 Blank test
Perform a blank test with the sample.
6.3 Determination
6.3.1 Place the sample (6.1) in a 250ml conical flask, add 5ml nitric acid (4.1), heat at low temperature to dissolve, remove nitrogen oxides, and cool. Add 16.0ml sodium chloride solution (4.3) to produce chloride precipitation and heat and boil for 3-5 minutes to make the precipitation condense, remove and cool, then add 10ml nitric acid (4.1). Filter the solution into a 100ml volumetric flask with slow quantitative filter paper and wash the conical flask and the precipitation with 20-25ml nitric acid (4.2) for more than three times.
6.3.2 Add 30 ml of thiourea solution (4.4) to a 100 ml volumetric flask (6.3.1) and dilute to the mark with nitric acid (4.2). Mix well. Leave for 15 min.
JB/T 7774.31995
6.3.3 Use a 3 cm cuvette at a wavelength of 445 nm on a spectrophotometer, measure its absorbance with water as a reference, subtract the blank absorbance, and find the corresponding bismuth amount from the working curve.
6.4 Drawing of the working curve
Put 0, 1.00, 2.00, 3.00, 4.00, and 5.00 ml of the standard solution (4.5) into 50 ml volumetric flasks, respectively, and add 8.0 ml of sodium chloride solution (4.3), 10 ml of nitric acid (4.1), and 15.0 ml of thiourea solution (4.4) to each. Dilute to the scale. Shake well. Let stand for 15 minutes. Use a 3 cm cuvette at a wavelength of 445 nm on a spectrophotometer, measure its absorbance with water as a reference, subtract the blank absorbance, and use the bismuth amount as the horizontal axis and the absorbance as the vertical axis. Coordinates, draw the working curve. Calculation of analysis results
The bismuth percentage is calculated as follows:
2m×10
Bi(%)=
Where:
m,——the amount of bismuth found from the working curve. mg; m. ——the mass of the sample, g.
8 Allowable difference
The difference in analysis results between laboratories should not be greater than the allowable difference listed in Table 1. Table 1
0.05~0.25
>0.25~0.5
Additional notes:
This standard was proposed and managed by the Gua Lin Electric Science Research Institute of the Ministry of Machinery Industry. This standard was drafted by Shanghai Alloy Material General Factory. This standard was drafted by Tianshui Great Wall Electrical Alloy Material Factory. The main drafters of this standard are Zhao Guangying, Li Yuren, Zhao Shiyu Chong
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