This standard specifies the method for determining the copper content in copper tungsten carbide vacuum contact materials. This standard is applicable to the determination of copper content in copper tungsten carbide vacuum contact materials. Determination range: 15.00% to 55.00%. JB/T 7775.1-1995 Chemical composition of copper tungsten carbide vacuum contact materials JB/T7775.1-1995 Standard download decompression password: www.bzxz.net

Mechanical Industry Standard of the People's Republic of China
Chemical analysis method of copper tungsten carbide vacuum contact material Iodine titration method for copper content
Subject content and scope of application
This standard specifies the method for determining the copper content in copper tungsten carbide vacuum contact material. JB/T7775.1—1995
This standard is applicable to the determination of copper content in copper tungsten carbide vacuum contact material, with a determination range of 15.00% to 55.00%. Reference Standard
JB4107.185 General principles and general provisions for chemical analysis methods of electrical contact materials 3 Method Summary
The sample is dissolved in sulfuric acid and ammonium sulfate, and potassium iodide solution is added to the weak acid medium to reduce Cu\+ to Cu+. The precipitated iodine is titrated with sodium thiosulfate standard solution using starch as an indicator to determine the copper content. 4 Reagents
Sulfuric acid (p1.84g/mL).
Ammonium sulfate solid.
Ammonium fluoride solution (200 g/mL).
Ammonium hydroxide solution (1+1).
Acetic acid (1+2) prepared with glacial acetic acid.
Potassium iodide solution (200 g/L).
Ammonium thiocyanate solution (200 g/L).
4.8 Preparation and calibration of sodium thiosulfate standard solution. 4.8.1 Preparation: Weigh 5.0 g of the reagent and dissolve it in 1 L of distilled water containing 0.2 g of anhydrous sodium carbonate that has just been boiled and cooled. After standing for one week, calibrate.
4.8.2 Calibration: Accurately weigh 0.0500g pure copper (99.95%) in a 250mL conical flask, add 10mL nitric acid (1+1), heat to dissolve, remove all nitrides, evaporate to near dryness, cool, add about 20mL water, and proceed as in 5.2.2 to 5.2.3. The concentration of sodium thiosulfate standard solution equivalent to copper is calculated according to formula (1): C=m
Where: bzxZ.net
Concentration of sodium thiosulfate standard solution equivalent to copper, g/mL; c
Weigh the amount of copper, g:
V—Volume of sodium thiosulfate standard solution consumed for calibration, mL. 4.9 Starch solution (5g/L), prepared as needed. 5 Analysis steps
5.1 Test materials
Approved by the Ministry of Machinery Industry on October 9, 1995
Implementation on January 1, 1996
JB/T7775.1~1995
Weigh three portions of test materials according to Table 1, accurate to 0.0001g. Table 1
Copper content
15.00~30.00
>30.00~55.00
5.2 Determination
Sample amount
5.2.1 Place the sample in a 250mL conical flask, add 5mL sulfuric acid (4.1), 2g ammonium sulfate (4.2), carefully heat to dissolve (to prevent splashing, a small funnel without a neck can be placed at the mouth of the bottle), cool to 70~80℃, add about 10~20mL water, and shake until the viscous colloid dissolves.
5.2.2 Add 5mL ammonium fluoride solution (4.3), neutralize with ammonium hydroxide solution (4.4) until the blue color of copper ammonia complex appears, and then add acetic acid (4.5) until the blue color of copper nitrogen complex disappears and 3mL is in excess. 5.2.3 Add 10 mL of potassium sulfonate solution (4.6), immediately titrate with sodium thiosulfate standard solution (4.8) until light yellow, then add 3 mL of starch solution (4.9), titrate until light blue, then add 10 mL of ammonium thiocyanate solution (4.7), and continue titrating until the blue color disappears (does not return to blue for one minute) as the end point. Record the volume of sodium thiosulfate standard solution titrated (mL). 6 Calculation of analytical results
The percentage of copper is calculated according to formula (2):
×100%
The concentration of sodium thiosulfate standard solution equivalent to copper, g/mL; where: C-
V——The volume of sodium thiosulfate standard solution consumed by the titration sample, mL; m-
The amount of sample, g.
7 Allowable difference
The difference in analytical results between experiments should not be greater than the allowable difference listed in Table 2. Table 2
15.00~30.00
>30.00~55.00
Additional Notes:
This standard was proposed and managed by Guilin Electric Science Research Institute of the Ministry of Machinery Industry. This standard was drafted by Shanghai Electric Science Research Institute of the Ministry of Machinery Industry. This standard was drafted by Tianshui Changcheng Electrical Alloy Material Factory. The main drafters of this standard were Zhao Guangying, Zhang Qingyi, Huang Liuqing, Tian Song Zhanfa
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