Three mercury board material: purple copper plates, silver plates and a silver-plated plate. Practice has proved that silver-plated copper plates have the best mercury-mixing effect and are most commonly used in industry.
The copper plating process includes copper plate shaping, plating solution and plating in a major step.
The thickness of the copper plate is generally 3 to 5 mm. In order to facilitate silver plating and replacement, and to facilitate the collection of gold , it is often cut into small pieces having a width of 400 to 600 mm and a length of 800 to 1200 mm. The copper oxide and the oil on the copper plate are removed by chemical or heating methods, and the convex and concave portions are flattened with a wooden shovel, and then removed and polished with burrs and marks by a wire brush and fine sandpaper.
The cut, polished, and polished copper plate becomes a silver-plated copper plate after being plated with silver oxide. The raw materials required for the preparation of 100 liters of electroplating solution are: 5 kg of electrolytic silver, 12 kg of potassium cyanide (purity 98 to 99%), 9 to 11 kg of nitric acid (purity of 90%), 8 to 9 of salt, and 10 liters of distilled water.
The preparation of the plating solution was carried out as follows.
1. Preparation of silver nitrate (AgNO 3 ) Silver: Nitric acid: water was mixed at a ratio of 1:1.5:0.5, and then heated to 100 ° C, and evaporated to obtain silver nitrate crystals.
2. Preparation of silver chloride (AgCl) After diluting the silver nitrate with water, add brine and stir well until the white precipitate disappears. The precipitate (AgCl) was then thoroughly washed to neutrality.
3. The potassium cyanide is diluted with distilled water to an aqueous solution of potassium cyanide, and then the prepared silver chloride is added. When the solution has a silver concentration of 50 g/liter and a cyanide concentration of 70 g/liter, it can be used as a plating solution.
The plating bath can be made into a rectangular slot by using materials such as wood, ceramic, cement or plastic plates, and the volume depends on the number of silver plated copper plates required.
6 to the cell voltage of 10 volts, a current density of 1 to 3 amps / cm 2. The required DC power can be supplied by a DC power generator or a silicon rectifier, or it can be powered by a 12-volt generator of the Jiefang brand. The anode of the electrolytic cell is an electrolytic silver plate and weighs 8 to 10 kg. The plating temperature is 16 to 20 °C. The thickness of the silver plated layer on the copper plate should be 10-15 microns.
When the mercury plate is used for too long, the local silver is detached, and the gold-trapping effect is significantly reduced. At this time, the softened mercury paste should be removed first, and the hard mercury paste should be scraped off with a hard shovel until the copper surface is exposed. Finally, scrape off the copper layer and re-silver. If the loss of the board surface is not suitable for reuse, it should be deepened to refine the gold and silver.
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