Asks an old paper by Ladislao Reti. From the journal Chymia, vol. 10, 1965, pages 11-23.
He runs through the usual well known sources of recipes for hydrochloric acid, such as Basil Valentine, De re Metallica etc, and ends up with a mid- 15th century Italian manuscript which is part of a work on dyeing, colours and the decorative arts.
It is translated by Mrs Merrifield as saying:
384. To soften bones. Take common salt and Roman Vitriol in equal quantities, and grind them together well: then distill them through an alembic and keep the distilled water in a vessel well closed. When you wish to soften bones or horn or ivory, put them in the said water for the space of five hours, and it will soften so that you may impress on them what you like, and they will afterwards become hard as before.
On the other hand to me it is not quite so amazing, knowing how much experimentation was going on at the time. Moreover what this recipe lacks is a link to theory and alchemical history. Alchemial works distinguish themselves by reference to an overarcing theory, and to historic experts, from Hermes to Albertus Magnus. This has neither, in a way it is simply a workshop reciept like Theophilus wrote 300 years earlier, lacking in detail since you are expected to already have your own workshop with equipment. I wonder too about the lack of mention of lute, alchemists usually swathed their cucurbic with lute in order to give it a longer life and prevent it breaking at high temperatures. When Lawrence Principe distilled salt he managed to melt a hole in the bottom of his pyrex glassware, but I don’t think he was using lute.
It certainly demonstrates how non-alchemists had distillation well in hand by that period, as we already know from the likes of “The goodman of Paris” and of course older ideas about spirits of wine being healthful, from the likes of Arnold of Villanova (the real one, not the pretend alchemical one) at the end of the 13th century.
More cross bearings on the use of such techniques by non-alchemists is always welcome. This particular recipe is apparently found in at least one more 15th century work from Italy, so it was likely to be well circulated.
Here’s a couple of photos of the alembic during my distillations. The top one is nitric oxide fumes for making nitric acid, and the bottom is water from distilling some iron acetate.