This method is based on the fact that concentrated sulfuric acid at a high temperature dissolves a metal such as silver and copper in the crude gold in the form of a sulfate, and the gold does not react, thereby achieving the purpose of purifying gold. The law requires that the gold content of the crude gold is not more than 33%. The content of lead is not more than 0.25% (the formation of lead sulfate is high due to lead high and the gold slag is used together to reduce the color of gold). The sulfuric acid method is similar to the nitric acid method, and is also subjected to melting, splashing, acid leaching, washing, drying, ingot casting, and several steps of replacement.
In the splashing of beads, special attention should be paid to the proper temperature. When the flame of the zinc vapor fuel on the surface of the alloy melt has been extinguished, and the white zinc oxide is gradually diluted by the thickening, this is the most suitable temperature for the splashing of the beads. When the beads are splashed, the water temperature should be at a low temperature, and the alloy pouring flow rate cannot be large. Otherwise, the "splashing beads" particles will be large, affecting the next acid leaching. The "splashing beads" are preferably in the form of flakes. When "splashing beads" are relatively hard and brittle, it means that there are more copper and lead impurities; if it is not brittle, it means less impurities. Before pickling, "throwing beads" should be dried in a cast iron container, and then added portionwise concentrated sulfuric acid, stirred digester at 160 ~ 180 ℃ 4 ~ 6 hours when the reaction iron surface foam disappeared began to appear white In the case of heavy smoke, the end of acid leaching is indicated. After the solution is cooled, the excess solution is poured out, and the sediment is washed with hot water until the water is clear (when the water is washed, it is covered with a pot to prevent the sulfuric acid from being sprayed and wounded). The washed sediment is further digested with concentrated sulfuric acid and washed with water, and repeated 3 to 4 times. Finally, the sediment is dried, smelted, and ingot cast. This method can obtain gold ingots containing 95 to 98% gold. The acid immersion liquid and the washing liquid are combined together, and the silver is first replaced by copper, and the copper is replaced by iron filings. The concentrated sulfuric acid consumption of this method is about 3 to 5 times the weight of the alloy. This method is less expensive than the nitric acid method.
Pro-Ser(tbu)-NH2,Fmoc-Ala-Ala-OH,Fmoc-Pro-Pro-OH,Fmoc-Gly-Gly-OH,Fmoc-Ile-Aib-OH
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