Chapter 5 Section 2 Copper smelting with bile water pioneered in ancient China

In the history of copper smelting in ancient China, in addition to pyrometallurgy, a unique "copper smelting method with gall water" also emerged. This technology is the harbinger of modern water metallurgy and an important invention in ancient China.This copper smelting method is to use metallic iron to replace copper from a solution containing copper compounds, then scrape it off, and then cook it to obtain copper ingots.The so-called "bile water" refers to natural spring water containing copper sulfate (commonly known as stone gall and gall alum in my country).It is formed because the natural copper sulfide ore is weathered and oxidized, and a part of it will generate soluble copper sulfate, which will dissolve and flow into the spring after being soaked and washed by groundwater and rainwater.As long as the concentration of copper in this kind of gall water is large enough, it can be used as a raw material for water copper smelting.

As early as the Han Dynasty, our ancestors had noticed the phenomenon that metallic iron could replace copper.For example, in the ancient book "Huainan Wanbishu" of the Western Han Dynasty, there is a record that "Zeng Qing (a copper carbonate mineral) gets iron, and then [iron] turns into copper".There is a saying in the Eastern Han Dynasty that "stone gallbladder can turn iron into copper".Ge Hong, an alchemist in the Eastern Jin Dynasty, made it more clear in his "Baopuzi Nei Pian": "Using Zengqing to coat iron, the iron is as red as copper,... and everything changes from the outside but does not change from the inside." But most of them at that time People do not have a precise understanding of this phenomenon, and mistakenly think that iron is transformed into copper when it comes into contact with Zeng Qing and stone gall.As late as the Tang Dynasty, some alchemists engaged in alchemy activities took advantage of this chemical change to heat and refine lithic gall water and mercury in a large iron pot, and the replaced copper and mercury formed an amalgam.Then, they heated the copper amalgam, which resembled sand grains, and steamed out the mercury to obtain red copper powder.They euphemistically call it "Red Silver", and they are very proud of themselves, thinking that the transformation of iron into copper has really been realized.This "unique skill" was recorded in "Dragon and Tiger Returning Alchemy" written by alchemist Jin Lingzi in the late Tang Dynasty.

Around the time of the Five Dynasties, "copper smelting with gall water" officially became a practical method for producing copper.In the Song Dynasty, this craft developed to a large scale.According to the "Song Huiyao · Shihuo Chapter", there were 11 areas where copper was smelted with gall water during the reign of Emperor Huizong of the Northern Song Dynasty, including Censhui in Shaozhou (in Guangdong), Qianshan in Xinzhou (in Jiangxi), and Dexing in Raozhou (also in Jiangxi). In Jiangxi) the three places are relatively large.In the second year of Chongning (AD 1103), the total output of bile copper in the country reached 1,874,427 jin, accounting for about 12% of the copper output at that time.However, after the Zhao and Song Dynasties moved to the south of the Yangtze River, the copper output of the 14 states in the south of the Yangtze River decreased sharply. However, the output of bile copper in the Qiandao period was still 210,000 jin, which accounted for 80% of the total copper output in the Southern Song Dynasty.Therefore, people in the Song Dynasty attached great importance to the production of gallbladder copper. Zhang Jia, a native of the Southern Song Dynasty, wrote a special book "The Essentials of Baptizing Copper" (which has been lost), which recorded the production of gallbladder copper at that time.Regarding the specific operation of leaching bile copper, there is a record in "Song History Shihuo Zhi": the pig iron is beaten into thin slices, discharged in a tank containing bile water, soaked for a few days, and then scraped out the precipitated muddy copper (called For "red coal"), into the furnace for refining.The efficiency at that time was about one catty of copper for every two catties of iron used, and the technical level was quite high.In addition, at that time there was also the "copper pouring method" that used gall soil to fry copper. The basic principle was the same as the "bili water method". Its benefits are already great", so it has been widely used.

In the Yuan Dynasty, these workshops using the copper leaching method gradually declined due to the limited water resources of the gallbladder springs and the consumption of a large amount of iron.There were some restorations in the Ming Dynasty, but the scale was not large.