There are two different types of Practical magick: Alchemy and Reagentry. Alchemy is the art of mixing herbs, minerals, liquids, and gases into salves, oils, incenses, tonics, ointments, elixirs, potions, powders, and other magickal elements, while Reagentry is the ability to use the natural properties of things in order to create immediate spell effects.
A laboratory is required for alchemy, but it is assumed that anyone who has the Alchemy skill will have such a laboratory with all the essential equipment in their home. Such a lab is not mobile. If an alchemist finds himself without a lab, he can use a regular chemistry lab such as might be found in a school or university with some penalty imposed by the GM. The only thing required for reagentry is the reagents to be used and a knowledge of what they do. Because Practical Magick is, well, practical, one does not have to be a Magician to perform it. An alchemist is weilding the natural magickal energy within his elements, not within himself.
No energy is required. The processes of alchemy and reagentry are the processes by which one uses the magickal energy already found within their elements. One may have to use multiple measures of an ingredient to increase its energy output. If, for example, the alchemist was creating a potion which, when thrown, would explode in a 25-foot radius, he would have to put enough of the element being used to equal 25 energy points. No range energy is required, since he will be throwing the vial, and no duration is required as it will create a real fire which burns until the real fire burns out.
A Reagentist may invoke the energies of the reagent by whatever means seem likely. For example, he may throw a powder, ingest a liquid, chew an herb or brew it into a tea, or apply a balm or an oil. Then, he rolls on Intellect modified by Reagentry . The result of this roll indicates the success rank of the effect of the reagent, modified by the rank of the reagent being used.
Alchemy involves extracting or altering the magickal essences of reagents and turning them into a form which can be used later. This requires samples of the reagents to be used, an appropriate chemical or alchemical lab, and, if necessary for the desired output, containers of some sort. The alchemist rolls on his Intellect modified by his Alchemy skill, and the result indicates the strength of the concoction.
The GM needs to be creative when dealing with odd mixtures. What happens if you mix a poison with a healing agent? The answer is entirely up to the GM. He may also add to this list mid-game by answering a character's Knowledge roll in regards to what reagent might be used for a particular spell effect.
To figure out what a reagentist or alchemist can use, the character must research the spell effect he wants to use or make a roll on something like Apothecary or Reagentry. One "pinch" (a basic unit of measurement for whatever the item is, usually about a half an ounce) will be equivalent to one energy point times the potency of the element being used. To determine the potency, the GM may simply make it up (if the character is buying it, better potency obviously equals more cost), but the general rule is to make a roll for whoever gathered the item. If the item is an herb, for instance, the person who picked it needs to roll on their Wortcunning skill modified by Dexterity. The result of this roll will equal the potency of the herb.