Ancient Chemistry Formulas Deciphered in China

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Knife coins used in China around 400 BC were some of those examined.

In a 2,300-year-old Chinese text, the components in chemistry formulas have been identified, revealing that ancient metallurgy was more complex than expected.

The Kaogong ji was written in China in the mid-1st millennium BC and is considered the oldest known technical encyclopedia. It details items ranging from swords to musical instruments and how to make them, including six chemical formulas for mixing bronze.

Dr. Ruiliang Liu of the British Museum said, “These formulas were used in the largest bronze industry in Eurasia during this period. Attempts to reconstruct these processes have been made for more than a hundred years, but have failed.”

The researchers were unable to identify the two main components: Jin and Xi. They were thought to be copper and tin, the two main components of bronze. But reconstructing the formulas with these components yielded metals that did not match the composition of ancient Chinese artifacts.

Now, research by Dr. Liu and Professor Pollard of Oxford University may have finally identified Jin and Xi. Their work, published in the journal Antiquity, shows that they were probably premixed alloys.

The discovery was made while studying the chemical composition of Chinese coins from the time the Kaogong ji was written. These were thought to have been made by diluting copper with tin and lead to produce the desired form of bronze.

Ancient Chemistry Formulas Deciphered in China 1
Depiction of a Chinese furnace producing copper and lead from a later text, Tian Gong Kai Wu from the Ming Dynasty.

But Professor Pollard and Dr. Liu found that the composition of the coins did not fit this technique. Instead, they found that the coins were made by mixing two pre-prepared metal alloys: a copper-tin-lead alloy and a copper-lead alloy.

This suggests that ancient Chinese bronze production involved a combination of alloys rather than pure metals. Therefore, Professor Pollard and Dr. Liu argue that this method of making bronze is also what Kaogong ji describes, and that Jin and Xi are referring to these premixed alloys.

“For the first time in over 100 years, we have produced a valid explanation of how to interpret the recipes given in the Kaogong ji for making Chinese bronze objects,” says Professor Pollard.

In addition to shedding light on the enigmatic ancient formula, the discovery also shows that ancient Chinese metallurgy was more complex than expected.

“The discovery points to an additional step in the production process of copper alloy objects in Early China – the production of pre-prepared alloys,” said Dr. Liu. This represents an extra, but previously unknown, layer in the metal production and supply network in China.”

The research also shows how science and analysis can help solve linguistic mysteries. The researchers hope that more studies like this one can continue to shed light on ancient texts.

Antiquity. August 10, 2022.

Article: Pollard, A., & Liu, R. (2022). The six recipes of Zhou: A new perspective on Jin (金) and Xi (锡). Antiquity, 1-14.

Ali Esen

Istanbul University, Department of Mathematics. Interested in science and technology.

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