Afterwards dissolve it by itself in a vessel with boiling water. Thus you have water of saltpetre. Water of sal ammoniac is made as follows: Calcine sal ammoniac and resolve it in a case on marble. This is water of sal ammoniac.
In order to make verdigris from copper there are several ways not necessary to recount here. We will therefore describe two only, with a twofold method of preparation, one for Medicine and the other for Alchemy. The verdigris used in medicine admits of the ensuing process: Take plates of copper, and smear them with the following compound: Take equal quantities of honey and vinegar, with a sufficient quantity of salt to make the three together the consistence of thick paste. Mix thoroughly, and afterwards put in a reverberatory, or in a potter's furnace, for the same time as the potter bakes his vessels, and you will see a black substance adhering to the plates. Do not let this circumstance cause you any anxiety or detain you at all; for if you suspend or expose those plates in the open air, in a few days the substance will turn green, and will become excellent verdigris, which may be called the balsam of copper, and is highly esteemed by all physicians. And this need not cause surprise, because the verdigris first becomes green in the air, and because the air has the power of transmuting a black colour into such a beautiful green. For here it should be known that, as daily experience in alchemy proves, every dead earth or caput mortuum, as soon as ever it comes out of the fire into the air, immediately acquires another colour, and loses its own colour which it had assumed in the fire. The changes of these colours are very diversified. According to the material such are the colours produced, though, for the most part, they flow from the blackness of dead earth. You who are skilled in Alchemy see that every dead earth, flux of powder, or of aqua fortis, comes black from the fire, and the more ingredients there are in it the more varied are the colours displayed in the air. Sometimes they only appear red, as vitriol makes them; sometimes only yellow, white, green, cerulean; sometimes mingled, as in the rainbow or the peacock's tail. All these colours display themselves after death, and as a consequence of death. For in the death of all natural things new colours appear, and they are changed from their first colour into another, each according to its own nature and properties. Moreover, we will say about verdigris that which we dedicate to Alchemy. The process of its preparation is as follows: Form very thin plates of copper, which stratify on a large tile with equal portions of sulphur and tartar, pounded and mixed. Reverberate for twenty-four hours with a strong fire, taking care that the copper plates do not melt. Then take them out; break the tile; expose the plates to the air, with the matter which adheres to them, for a few days, and the matter on the plates will be converted into most beautiful verdigris, which in all strong waters, in waters of gradations, in cements and colourings of gold, tinges gold and silver with a deep colour.
But in order that copper may become æs ustum, which is also called the crocus of copper, the following process must be adopted: let copper be formed
