What alchemists were trying to do
Alchemy was a mix of practical craft, natural philosophy and, for many practitioners, spiritual aspiration. It is best known for two goals. The first was transmutation: changing base metals such as lead or copper into silver or gold. The second was the search for an elixir, sometimes called the philosopher’s stone, that could perfect metals and, in some accounts, heal the body or prolong life.
These goals were not absurd within the thinking of the time. If all matter was built from the four elements in different proportions, then changing the proportions might, in principle, change one substance into another. Metals were widely thought to grow slowly in the earth toward gold, and alchemy was imagined as a way of speeding up nature. A common theory, passed on from Islamic writers, held that metals were composed of principles associated with sulfur and mercury, and that adjusting them could alter the metal.
Nobody has ever made gold from lead by these methods, and it is worth saying clearly that the central goal failed. The interest lies in what was learned along the way.
The laboratory
The alchemist’s workspace looked something like a small workshop. Its main features were furnaces and glassware, many of which are ancestors of later laboratory equipment.
- Furnaces. Fires of charcoal were controlled to give steady, gentle heat or a strong blast. A furnace sometimes called an athanor was designed to burn for long periods, since many procedures were described as lasting days or weeks. The practical skills overlapped with those of the blacksmith forge, and metalworkers and alchemists probably shared techniques and tools.
- Crucibles and cupels. Small heat-resistant pots held metals while they were melted, and porous cups were used to separate precious metals from lead in assaying.
- Alembics and retorts. Distillation apparatus heated a liquid so that its vapor could be collected and cooled into a purer form. The very word alembic comes from Arabic.
- Flasks and vessels. Glass or glazed containers held mixtures during heating or digestion, a term for slow, gentle warming.
- Water baths and sand baths. Placing a vessel in warm water or sand allowed careful control of temperature.
Many words from this world entered European languages from Arabic through translation, including alchemy itself, alkali and alcohol. That vocabulary is itself a sign of how much the practice owed to Islamic writers, whose texts were translated into Latin from the twelfth century on.
Processes and experiments
Alchemical texts describe many operations, often in coded or symbolic language. Common ones included distillation, sublimation (turning a solid directly into vapor and back), calcination (heating a substance to a powder), dissolution and filtration. The writing frequently used images such as a green lion, a king or a dragon for particular substances or stages, which makes interpretation hard even for specialists.
Experiments were generally trial and error, sometimes recorded in recipes, and often repeated by following the text of earlier authorities. This was not systematic testing in the modern sense, but it did involve handling materials, noticing changes in color, smell, texture and weight, and recording sequences of steps.
Lasting contributions
Several practical results are usually credited, with some caution, to the alchemical tradition.
- Distillation. Improved methods of distilling led to alcohol-based preparations and aromatic waters. These had uses in perfumery, cookery and, above all, medicine.
- Mineral acids and strong solvents. Texts from the later Middle Ages describe acids able to dissolve metals. The exact origins and authorship of these discoveries are debated, but they extended the range of chemical operations available.
- Metallurgy and assaying. Testing the purity of gold and silver was a practical need for mints and goldsmiths, and the methods overlapped with alchemical ones.
- Pigments and dyes. Making pigments such as vermilion from mercury and sulfur involved chemical processes familiar to alchemists, and craftspeople preparing parchment and pigments worked with similar materials.
- Medicine. Some alchemists tried to prepare mineral and distilled remedies, and this strand developed further after the medieval period. The links to medieval medicine were close, though many remedies were of doubtful value and some were poisonous.
- Laboratory habits. The use of standard equipment, repeated operations and written procedures helped establish chemistry as a hands-on discipline.
Mixed reputation
Alchemy was not universally admired. Critics doubted whether metals could really be transmuted, and the claims of fraudulent practitioners who promised gold made the subject suspect. Church and royal authorities sometimes tried to regulate it, mainly out of concern about counterfeiting and deception. Even so, serious scholars, including churchmen and university masters, wrote about it. Writers such as Geoffrey Chaucer later made fun of cheating alchemists in literature, which shows how familiar the type had become.
From alchemy to chemistry
The line between alchemy and chemistry was not sharp in the Middle Ages and remained blurred long afterward. The word chemistry itself descends from the same roots. Over the following centuries, practitioners gradually dropped the goal of transmutation, attached more weight to measurement and shifted toward the study of substances and reactions. That transition belongs mostly to the early modern period. What the medieval alchemists provided was a body of equipment, techniques and vocabulary, along with a habit of working directly with materials, that later chemists could build upon.