This standard specifies the determination method of aluminum content in silver zinc oxide electrical contact materials. This standard is applicable to the determination of aluminum content in silver zinc oxide electrical contact materials. Determination range: 0.05% to 0.10%. JB/T 7774.2-1995 Chemical analysis method for silver zinc oxide electrical contact materials JB/T7774.2-1995 Standard download decompression password: www.bzxz.net

Mechanical Industry Standard of the People's Republic of China
Chemical analysis method for silver zinc oxide electrical contact materials Chrome azuro blue S spectrophotometric method for determination of aluminum content
1 Subject content and scope of application
This standard specifies the method for determination of aluminum content in silver zinc oxide electrical contact materials. JB/T7774.21995
This standard is applicable to the determination of aluminum content in silver zinc oxide electrical contact materials. Determination range: 0.05% to 0.10%. 2 Reference standards
GB7729-87
General rules for spectrophotometric methods for chemical analysis of metallurgical products JB4107.1-85 General rules and general provisions for chemical analysis methods of electrical contact materials 3 Principle of the method
Use nitric acid to dissolve the sample, treat the residue with potassium pyrosulfate, take part of the solution, add thiourea, ascorbic acid, gum arabic, chrome azuro blue S, use ammonium acetate buffer solution to control the pH, so that aluminum [IJ and chrome azuro blue S form a complex, and measure its absorbance at a wavelength of 610nm on a spectrophotometer.
4 Reagents
4.1 Potassium pyrosulfate.
4.2 Nitric acid (1+1).
4.3 Thiourea solution (50g/l).
4.4 Ascorbic acid solution (10g/l).
4.5 Gum arabic solution (5g/l).
4.6 Chrome azure S solution (2g/1), if there is insoluble residue when dissolved in water, filter it before use. 4.7 Ammonium acetate buffer solution (200g/1). 4.8 Paper pulp (soaked with quantitative filter paper).
4.9 Aluminum standard stock solution (0.05g/1). Preparation: Weigh 0.8792g of potassium aluminum sulfate [Alz(SO),·K,SO,·24H,O], dissolve it in water and transfer it into a 1000ml volumetric flask and dilute to the mark. Shake well. This standard solution contains 0.05mg aluminum in 1ml. 4.10 Aluminum standard solution (0.01g/1).
Pipette 20.00ml of aluminum standard stock solution (4.9) into a 100ml volumetric flask, dilute to the mark, and shake well. This solution contains 0.01mg aluminum in 1ml.
4.11 Silver solution (10g/1).
Weigh 2.50g pure silver (99.95%) and place it in a 250ml conical flask. Add 10ml nitric acid (4.2) and heat to dissolve and evaporate to about 3ml. Cool and transfer to a 250ml volumetric flask and dilute to scale. Shake well. This solution contains 10mg silver in 1ml. 4.12 Zinc solution (2g/1).
Weigh 0.50g pure zinc (99.95%) and place it in a 250ml conical flask. Add 5ml nitric acid (4.2) and heat to dissolve and evaporate to about 3ml. Cool and transfer to a 250ml volumetric flask and dilute to scale. Shake well. This solution contains 2mg zinc in 1ml. 5 Instruments
Spectrophotometer.
Analysis steps
6.1 Test material
Weigh about 0.5g of test material, accurate to 0.0001g. 6.2 Blank test
Perform a blank test with the test material. Www.bzxZ.net
6.3 Determination
6.3.1 Place the test material (6.1) in a 250ml beaker and add 10ml of nitric acid (4.2), heat to dissolve, evaporate to near dryness, and cool to room temperature. Add 25ml of water to dissolve the salts, add about one ox-horn spoon of pulp (4.8) and stir, heat to boil, and filter into a 250ml volumetric flask with quantitative filter paper. Wash the beaker and filter paper three times each.
6.3.2 Transfer the precipitate and filter paper into a platinum crucible, heat until the filter paper in the crucible is dry, transfer it into a muffle furnace, burn it at a furnace temperature of 700-800℃ until it turns to ashes, take it out and cool it, add 2g potassium pyrosulfate (4.1) and melt it at a furnace temperature of 650-700℃ for 30min, take it out and cool it to room temperature, use warm water to remove the melt in the platinum crucible, merge this solution into the filtrate (6.3.1), and dilute to the scale. Shake well. 6.3.3 Transfer 10.00ml of solution (6.3.2) into a 100ml volumetric flask, add 5.0ml of thiodol solution (4.3), 2ml of ascorbic acid solution (4.4), 2ml of gum arabic solution (4.5), 2ml of chrome blue S solution (4.6) and 8ml of ethylammonium buffer (4.7), and dilute to the scale. Shake well. Let it stand for 25min to 30min. Use 1 cm colorimetric blood at a wavelength of 610 nm on a spectrophotometer and measure its absorbance with water as reference. 6.3.4 Subtract the absorbance of the blank reagent from the absorbance of the sample and find the corresponding amount of aluminum from the working curve. 6.4 Plotting the working curve
Pipette 0, 0.50, 1.00, 1.50, 2.00, 2.50 ml of aluminum standard solution (4.10) into 100 ml volumetric flasks respectively, add 2.0 ml of silver solution (4.11) and 1.0 ml of zinc standard solution (4.12) to each, and proceed as in 6.3.3. Subtract the absorbance of zero concentration, draw the working curve with the aluminum amount as the horizontal axis and the absorbance as the vertical axis. 7 Calculation of analysis results
The percentage of aluminum is calculated as follows:
Al(%)= M, . V, : 10--
m:V.
M,-—Aluminum content is obtained from the working curve, mg Where:
V total volume of sample solution, ml;
V. —Volume of sample solution, ml;
Mass of 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
0.050~0.070
>0.070~0.100
Additional instructions:
JB/T7774.21995
This standard is proposed and managed by the Guilin Electrical Science Research Institute of the Ministry of Machinery Industry. This standard is drafted by Shanghai Alloy Material General Factory. This standard is drafted by Tianjin Electrical Alloy Factory. The main drafters of this standard are Zhao Shiyu
Zhao Guangying
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