Chinese history of cupronickel

The author-scholar Ho Wei describes most exactly the process in circa 1095 CE, which suggest the Chinese were not aware that nickel was a metal in its own right. The paktong alloy was described as being made from adding small pills of naturally-occurring "Yunnan" ore to a bath of molten copper. When a crust of slag formed, saltpeter was added, the alloy stirred and the ingot immediately cast. Zinc is mentioned as an ingredient — but not detailed when exactly it was added. The ore used is noted as solely available from Yunnan, related from the story:

San Mao Chun were at Tanyang during a famine year when many people died, so taking certain chemicals, Ying projected them onto silver, turning it into gold, and he also transmuted iron into silver — thus enabling the lives of many to be saved [through purchasing grain through this fake silver and gold] Thereafter all those who prepared chemical powders by heating and transmuting copper by projection called their methods "Tanyang techniques".[5]

The late Ming and Ching literature have very little information about paktong. However, it is first mentioned specifically by name in the Thien Kung Khai Wu of circa 1637:

When lu kan shih (zinc carbonate, calamine) or wo chhein (zinc metal) is mixed and combined with chih thung (copper), one gets 'yellow bronze' (ordinary brass). When phi shang and other arsenic substances are heated with it, one gets 'white bronze' or white copper: pai thong. When alum and niter and other chemicals are mixed together one gets ching thung: green bronze.[5]

Ko Hung of the 300 CE stated:" The Tanyang copper was created by throwing a mercuric elixir into Tanyang copper and heated- gold will be formed." However, the Pha Phu Tsu and the Shen I Ching describing a statue in the Western provinces as being of silver, tin, lead and Tanyang copper — which looked like gold, and could be forged for plating and inlaying vessels and swords.[4]

Needham et al. argue that cupro-nickel was at least known as a unique alloy by the Chinese during the reign of Liu An in 120 BCE in Yunnan. Moreover the Yunnanese State of Tien was founded in 334 BCE as a colony of the Chu. Most likely modern paktong was unknown to Chinese of the day — but the naturally occurring Yunnan ore upro-nickek alloy was likely a valuable internal trade commodity

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