This is something we would not think of otherwise. However, 2400 years ago Chinese alchemy, or more properly Chinese Chemistry was at the height of its prestige and investment. This led to a number of discoveries that are been just now coming back into our knowledge base. Not least because it was deliberately well hidden through obscure codes.
This is one of their discoveries and an important one before the modern era.
All good stuff recently rediscovered and understood.
Han Purple: A 2,800-year-old artificial pigment that quantum physicists are trying to understand
Traces of Han purple can still be seen on many of the terracotta warriors (realhistoryww.com)