In the image of the crucifixion we see an alchemical process where the "Good Thief" begins as a mocker but changes his tune. To this Good Thief, Christ says, "Truly, I say to you, today you will be with me in Paradise." The other thief, though, remains a mocker, and will be thrown into the fire.
In alchemy, this mirrors the process of distillation. Alchemical mercury and sulfur (oil and alcohol) both distill readily when heated. This is Christ and the Good Thief. But the bad thief is the "mark" -- the leftover plant materials after extracting the distillate. In distillation we have a "lifting up" of the inner qualities of whatever reagent with which we are working.
The leftovers that don't distill must be burned at high temperatures called "calcination" (from the word chalk). The soluble salts must be extracted from what has been burned, because even in what is discarded, there is something valuable. This trace amount of valuable salt is called alchemical "salt." A spagyric is when these have been separated, purified, and then reunited. With the reunion of the salt element of the bad thief, a new sacred body is made. In this, alchemy is an imitation of the spiritual image presented at the crucifixion.
In Orthodox depictions of the cross, there is a notable slant at the foot platform. This is an indication of the dividing path: yes, all have sinned and fallen short of the glory of God, but there are those who recognize that and those who remain recalcitrant. Do we belong to the distillate or the part that must be fired?