The mud lumps of sulfur and ore heating, to 200 degrees Celsius when raw sulfur melting, filter out the material did not melt (can be omitted), continue to heat, stirring constantly, so that some of the impurities vaporised evaporation off, to 400 degrees Celsius sulfur boiling, collecting sulfur gas, the sulfur gas cooling and solidification, you can get the purer sulfur.
Song Yingxing at the end of the Ming Dynasty, 'Tiangongkaiwu', a more specific account of pyrite as raw material for burning sulfur technology. The general steps of calcining sulphur are: first, the ore is wrapped with coal cake and stacked up, and the outside is rammed with clay and a furnace is built. Each furnace has about 1,000 kilograms of stone and coal cake, the furnace is covered with old slag from burning sulphur, and the top of the furnace is lowered in the middle to leave a round hole. When it burns to a certain degree, a golden-coloured gas will come out of the hole in the furnace. In advance, the potter is asked to burn a bowl with a central bulge, the edges of which are rolled inwards to form a groove like fish fat, and when burning sulphur yellow, the bowl is covered with the hole in the furnace. The yellow vapour of sulphur rises along the furnace hole, is blocked by the bowl and can not run away, so it condenses into a liquid, flowing into the groove along the inner wall of the bowl, and through the eyelets along the cooling pipe into a small pool, and finally condenses and becomes solid sulphur.
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