Making It and Using It

Sal Alembroth was made by combining corrosive sublimate, mercuric chloride prepared by subliming mercury with vitriol and common salt, together with sal ammoniac, dissolving both in water and recrystallizing the mixture into clear, glassy, extremely corrosive crystals. The name alembroth is obscure in origin, possibly a corruption of an Arabic or a garbled alchemical coinage, and the honorific salt of wisdom or sal sapientiae attached to it in Latin texts reflects the esteem in which practitioners held its dissolving power rather than any claim to a literal philosophical meaning. It was used as a flux and menstruum in metallic work, valued for its ability to attack and combine with metals that resisted simpler acids, and it appears repeatedly in recipes attributed to or associated with the alchemist Basil Valentine and other writers working in the German and central European tradition of metallic alchemy.

Handling it required real caution given its mercury content, though early modern texts do not always dwell on the danger with the seriousness a modern reader would expect; mercuric chloride is severely toxic, and any preparation combining it with a volatile ammonium salt carries the hazards of both. Its reputation as a philosophical or spiritual salt, beyond its practical chemistry, likely owes something to the sheer difficulty and prestige of the combination it represented.