This standard specifies the determination method of cadmium content in silver cadmium oxide electrical contact materials. This standard is applicable to the determination method of cadmium content in silver cadmium oxide electrical contact materials. Determination range: 5.00% to 25.00%. JB/T 7776.1-1995 Chemical analysis method for silver cadmium oxide electrical contact materials JB/T7776.1-1995 Standard download decompression password: www.bzxz.net

Mechanical Industry Standard of the People's Republic of China
Chemical analysis method of silver cadmium oxide electrical contact material EDTA complexometric titration method for determination of cadmium content
1 Subject content and scope of application
JB/T7776.1-1995
Replaces JB4107.3--85
This standard specifies the method for determination of cadmium content in silver cadmium oxide electrical contact material. This standard is applicable to the determination of cadmium content in silver cadmium oxide electrical contact material. Determination range: 5.00%~25.00%. 2 Reference standards
JB4107.1--85 General principles and general provisions for chemical analysis methods of electrical contact materials 3 Principle of the method
The sample is decomposed with nitric acid and silver is separated in the form of silver chloride precipitation. Add an excess of EDTA standard solution to the test solution with a pH of 5.5~5.8, and titrate the excess EDTA with zinc acetate standard titration solution. Then add enough potassium iodide to make potassium iodide and cadmium [I] form a more stable [CdI.\ complex anion and release the corresponding EDTA. Use dimethyl phenol orange as an indicator and titrate with zinc acetate standard titration solution to calculate the amount of cadmium. The added elements zinc, aluminum, tin, magnesium, nickel and etc. in the alloy do not interfere with the determination. 4 Reagents
4.1 Potassium iodide (solid). bZxz.net
Nitric acid (1+1).
Ammonia water (1+1).
Sulfur gland solution (100g/1).
4.5 Sodium chloride solution (50g/1).
Hexamethylenetetramine solution (300g/1).
4.7 Disodium ethylenediaminetetraacetic acid standard solution [C(CoHN,O.Na:·2H,O)0.01mol/L]. Weigh 3.72g EDTA and place it in a 400mL beaker, dissolve it with hot water, and cool it to room temperature. Transfer it to a 1000mL volumetric flask, dilute to the mark, and mix well. 4.8 Cadmium standard solution: Weigh 1.0000g pure cadmium (99.95%) and place it in a 250mL beaker, add 20mL nitric acid (4.2), cover with a watch glass, heat at low temperature to dissolve, drive off nitrogen oxides, and cool to room temperature. Transfer it to a 1000mL volumetric flask, dilute to the mark, and mix well. This solution contains 0.001g pot in 1mL.
4.9 Zinc acetate standard titration solution (C[Zn(CH,·COO),·2H,OJo.01tnol/L). 4.9.1 Preparation: Weigh 2.2g zinc acetate [Zn(CH,·COO):·2H,O] into a 250mL beaker, dissolve in water, add 5mL acetic acid (36%), transfer to a 1000mL volumetric flask, dilute to scale, and mix. 4.9.2 Calibration: Transfer three portions of 10.00mL of cadmium standard solution (4.8), place each portion in a conical flask and add 50mL of water. The following operations are carried out according to Section 5.2.3. When the extreme value of the volume of zinc acetate standard titration solution consumed by the three portions of cadmium standard solution does not exceed 0.05mL, take the average value.
The actual concentration of zinc acetate standard titration solution is calculated according to formula (1): Co·V.
Cv.xo.1124
Approved by the Ministry of Machinery Industry on October 9, 1995
Implemented on January 1, 1996
In the formula:
JB/T7776.1-1995
Concentration of cadmium standard solution for Co calibration, g/mL; Vo—volume of the standard solution of saw removed, mL; V,—volume of zinc acetate standard titration solution consumed in the second titration, mL; 0.1124----mass of cadmium equivalent to 1.00mL zinc acetate standard titration solution (C[Zn(CH,·COO),·2H,O]=1.00mol/L), g.
The xylenol orange solution (18/L) should not be used for more than one week after preparation. 4.10
5 Analysis steps
5.1 Test material
Weigh 1g of test material, accurate to 0.0001g.
5.2 Determination
5.2.1 Place the test material (5.1) in a 250mL beaker, add 10mL of nitric acid (4.2), cover with a watch glass, heat at low temperature to dissolve, drive out all nitrogen oxides, and cool to room temperature. Transfer to a 100mL volumetric flask, dilute to the mark, and mix well. 5.2.2 Control the amount to about 10mg. Take aliquots of the test material solution, add 2mL of sodium chloride solution (4.5) to a 100mL beaker, and a silvery white precipitate of chloride will form in the solution. Filter into a triangular flask with medium-speed qualitative filter paper, wash the wall of the cup and the precipitate with water 34 times, discard the precipitate, and the volume of the filtrate is about 80mL.
5.2.3 Add 1mL of sulfur gland solution (4.4), 15mL of hexamethylenetetramine solution (4.6) to the filtrate, add 6 drops of xylenol orange solution (4.10), add 15mL of DTA standard solution (4.7), and shake well. At this time, the solution changes from purple-red to bright yellow. Then use ammonia water (4.3) to adjust the color to purple-red, and use nitric acid (4.2) to adjust the color to bright yellow. Heat to 35-45℃. Titrate with zinc acetate standard titration solution (4.9) until the color changes from yellow to purple-red (do not count). Then add 30g of potassium iodide (4.1), heat the solution slightly and turn it to bright yellow again (if the solution is not bright yellow, add nitric acid (4.2) until it is bright yellow). Titrate with zinc acetate standard titration solution (4.9) until the color turns purple-red as the end point, and record the volume of zinc acetate standard titration solution consumed.
Calculation of analysis results
The percentage of cadmium is calculated according to formula (2),
CV. .V,x0.1124,
x100:
Wherein:
C--actual concentration of zinc acetate standard titration solution, mol/L; V. Volume of zinc acetate standard titration solution consumed in the second titration, mL; V,--sample solution dilution volume, mL;
V,--sample solution volume, mL,
sample mass, g;
7Allowable difference
--mass equivalent to 1.00mL zinc acetate standard titration solution (C[Zn(CH,·COO),·2H,O]=1.00mol/L), g.
The difference in analysis results between laboratories should not be greater than the allowable difference listed in Table 1. Table 1
5.00~10.00
>10.00~15.00
>15.00~20.00
>20.00~25.00
Allowance
Additional Notes:
JB/T7776.1-1995
This standard is proposed and managed by Guilin Electric Science Research Institute of the Ministry of Machinery Industry. This standard is drafted by the State-owned No. 615 Factory. This standard is drafted by Jinan Electrical Alloy Factory. The main drafters of this standard are Qin Guangting, Liu Chengjun and Li Bingkuan
From the date of implementation of this standard, the original JB4107.3-85 "Determination of cadmium content in silver cadmium oxide" will be invalid.
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