This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
An alchemical substance entry records a specific material named and worked with in the alchemical tradition, a salt, an acid, a metal or a compound prepared through a documented laboratory process, distinct from a purely symbolic or mythological substance in having an actual, reproducible chemical identity alongside whatever additional meaning alchemical writers attached to it. Lawrence Principe's modern scholarly treatment of alchemy insists on taking this laboratory side seriously rather than reading every alchemical text purely as coded spiritual allegory.
An entry records a substance's documented preparation, what raw materials and what process produced it, its properties as alchemical writers described them, and, where it is known, a substance's modern chemical identity, since a name like aqua regia or spirit of salt names a real, specific compound with a plain chemical identity a modern reader can check against the alchemical account.
Alchemical writers very often layered symbolic meaning onto a substance alongside its practical use, a metal standing for a planet, a color change marking a stage of inner transformation, and the entry records both layers, the material fact and the meaning a tradition attached to it, as two separate, both worth recording, facts about the same substance.