1. 炼金术；炼丹术
Alchemy was a form of chemistry studied in the Middle Ages, which was concerned with trying to discover ways to change ordinary metals into gold.

2. （改变事物的）魔力
Alchemy is the power to change or create things in a way which seems mysterious and magical.

1. a pseudoscientific forerunner of chemistry in medieval times

2. the way two individuals relate to each other

e.g. their chemistry was wrong from the beginning -- they hated each other
a mysterious alchemy brought them together

Synonym: chemistryinterpersonal chemistry