What is empirical evidence and what's is it not

Empirical evidence is information acquired by observation or experimentation. This data is recorded and analyzed by scientists and is a central process as part of the scientific method.
As example of not empirical evidence:
Language, letters, words, truths, numbers, logic, mathematics, on and on.
All of these things do not have empirical existence. They exist only in the mind.

The answers would be: 1: the liquid only contains one compound4: the liquid is a pure substance