Alchemiae Gebri Arabis philosophi solertissimi, libri, cum reliquis, ut versa pagella indicabit

frozen, let it be calcined for a day and a night in a medium fire, and keep it thus sufficiently purified.

Purification of alkali salt.

Alkali salt is purified like common salt, and it is the fat of glass often refers to potash or soda ash used in glassmaking. First, let it be ground, and let it all be dissolved in common warm water; afterwards let it be distilled through a filter, and frozen, and calcined with a slow fire.

Purification of rock salt.

First, let it be ground; then let it be done as with common salt.

Purification of sal ammoniac.

Let it be ground first with the preparation of purified common salt. Afterwards, let it be sublimed in a high aludel sublimation vessel, until it has been extracted totally pure. Afterwards, let it be dissolved upon porphyry, in the open air, if you wish to make water from it, or let it be kept as it is, sublimed and sufficiently pure.

Purification of other salts.

Diverse kinds of salts are still found, which are prepared and purified by the method already said.

Purification of alums.

First, concerning glacial alum a type of rock alum. Many things can be prepared through it without any purification of it itself. Nevertheless, it is purified in this manner: Let it be placed in an alembic distilling apparatus, and let all the moisture be extracted from it, which is worth much in this art. Let the dregs remaining in the bottom of the vessel either be dissolved upon a stone in some humid place, or in the water extracted from it, or let them be reserved.

Purification of Jamenian alum.

Jamenian alum is prepared just as glacial, except that it is of greater virtue in this art.