Like chemists, alchemists work with an element they call ‘salt’. But what they call salt and what they call mercury and sulphur have nothing in common with the chemical substances of the same name.
Only the correspondences between them are the same: just as salt is the product of an acid and a base in chemistry, it is the product of sulphur and mercury in alchemy.
Sulphur must be seen as the masculine principle which manifests as our intellect and on the plane above, as our spirit; mercury represents the feminine principle, our heart and higher still, our soul. And salt, our will, represents the balance that should ideally reign between the two.
Will is expressed through actions: through their actions, humans reveal the extent to which they have been able to create harmony between their intellect and their heart, and between their thoughts and feelings. Through their physical body, they express the wealth of their spirit and soul, of which their intellect and heart are the instruments.
And by means of their physical body, the instrument of their will, humans must bring the Divine down on to the earth.