because it no longer has the form of gold, but is a white metal like fixed silver.
But now let us go on to lay before you by what means the mortification of the metals is brought about. First of all, it should be known concerning iron that it can be mortified and reduced to a crocus in the following way: Form very thin plates of steel, beat them red hot, and then extinguish them in vinegar made from wine. Keep on doing this until you see the vinegar has become very red. When you have enough of this red vinegar, pour it all out, and distil therefrom the moisture of the vinegar. Coagulate the residuum into a dry powder. This is the most excellent Crocus of Mars. There is, however, another way of making the Crocus of Mars which partly surpasses the former, and is carried out with much less expense and labour, thus: Stratify very thin plates of steel with equal quantities of sulphur and tartar. Afterwards reverberate. This produces the most beautiful crocus, which should be taken from the plates.
In the same way you should be informed that if any plate of iron or steel be smeared over with aqua fortis, it renders also a beautiful crocus. Such is the result, too, with oil of vitriol, water of salt, water of alum, water of sal ammoniac, water of salt nitre, sublimated mercury, all of which mortify iron, and reduce it to a crocus; but none of these methods is to be compared with the two mentioned above; for they can only be used in Alchemy and not in medicine; so use in preference the first two methods, and avoid the rest.
The mortification of copper, to reduce it to vitriol, verdigris, or burnt brass, can also be accomplished in various ways; and there are various processes with this metal, too, but one is better and more useful than another. Wherefore it will be well to make a note of the best and most useful, and to say nothing about the others. The best, easiest, and most reliable method of reducing copper to vitriol is as follows: Let plates of copper be smeared with water of salt or of saltpetre, and hung or exposed in the air until the plates begin to become green. Wash off this greenness with clear spring water, dry the plates with a rag; again smear the plates with water of salt or saltpetre, and again proceed as before, repeating the process until the water becomes quite green, or sends forth much vitriol to the surface. Then remove the water by tilting the vessel, or by drawing it off, and you will have an excellent medicinal vitriol. For Alchemy, there is no more beautiful, noble, or better vitriol than that which is made by aqua fortis, or aqua regis, or water of sal armoniac. Proceed thus: Let plates of copper be smeared with one of the aforesaid waters, and as soon as the greenness has been extracted, and the plates have been dried, let the greenness be taken off with a hare's foot, or by some other means at pleasure, as white lead is scraped off leaden plates. Let them be again smeared as before, until the plates are entirely consumed, and thence is produced a very beautiful vitriol, such as you cannot fail to admire.
Water of saltpetre is made thus : Purify saltpetre, liquefy and pulverise it.
