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An important advancement in chemistry came with the invention/ discovery of the mineral acids, distilled from vitriol or saltpetre. This probably occurred in the 13th century, in Spain or Africa. It then took until the 14th century before the recipes spread into Europe, and by the 16th century we find that non-alchemists are using acids to dissolve metals and suchlike. Dissolving metals and other substances had been an important part of alchemy since at least Arabic alchemy in the 9th century, but it was fiddly and time consuming, whereas mineral acids could dissolve almost everything without much trouble, including gold!

Some of the early recipes, since they use both alum and saltpetre and vitriol are likely to produce a mixture of sulphuric and nitric acids, and possible some hydrochloric too, depending on what else was present. And they varied, how much so is the subject for another post.

But by the late medieval or early post medieval, they had definite, regularly used recipes for nitric acid. This one comes from the altered ‘Compound of Compounds’, (or Compositum de Compositis).
As I have explained before,, the later version of the Compound is from probably the 16th century, definitely before 1613 when it was printed in the Theatrum Chemicum.

It is the start of a coherent set of recipes for reducing mercury down to the prime matter, without any qualities, before reconstituting it into gold or silver or a stone capable of making gold or silver out of other metals. I’ll work through the series of recipes over this summer and see how well it turns out.

So, first you need 2lbs each of saltpetre and green vitriol, and 1lb of calcined alum.
Not that my alembic is that big, so I reduced the quantities but kept the proportions the same. These should be ground together and put into the cucurbit, which you see here in the furnace with the alembic on top:
nitric acid making cucurbit

Because this is a high temperature distillation I’ve covered it with lute to support it and prevent damage.
Next, you apply heat, I was surprised how quickly it warmed up with the use of a small amount of wood in the fire, and see orange fume starting:
nitric acid making fumes appearing

Then more:
nitric acid making more fumes

Ultimately it ended up like this strange red colour:
nitric acid making red alembic

These are nitrous oxides, the odd thing being that at no point did the apparatus turn white as the instructions said it should. Maybe I didn’t seal it well enough and it would be white without excess oxygen getting in? Anyway, I collected a clear liquid, bubbling the orange vapours through it.

When tested, this liquid had a pH of 1:
nitric acid making pH paper

The instructions say it has a greenish colour, and it sort of does, although it is a little hard to see.
The text says that this water is “…the solvent of the Moon; conserve it for the Opus; it dissolves silver and separates it from gold. It calcines Mercury and the Crocus of Mars; it imparts to the skin of a man a brown colouration, of difficult removal. It is the primal water of the philosophers, perfect to the first degree.”

Cool, I’ve got some primal water. I will make some more, this didn’t produce very much, then the recipe says to add sal ammoniac to it, which should make it go yellow, and instead of dissolving silver, it will also dissolve gold. This would be because of the addition of chlorine ions, making aqua regia, which can dissolve gold as readers of Arthur Ransome’s “Pigeon Post” will recall.