He was obliged to learn, in a general way, many of the same things that must be understood in either chemical or alchemical laboratories.

The general knowledge that certain liquids vaporize at lower temperatures than others, and that the melting-points of metals differ greatly, for example, was just as necessary to alchemy as to chemistry.

The knowledge of the gross structure, or nature, of materials was much the same to the alchemist as to the chemist, and, for that matter, many of the experiments in calcining, distilling, etc., were practically identical.
To the alchemist there were three principles--salt, sulphur, and mercury--and the sources of these principles were the four elements--earth, water, fire, and air.

These four elements were accountable for every substance in nature.

Some of the experiments to prove this were so illusive, and yet apparently so simple, that one is not surprised that it took centuries to disprove them.