Vitriol in the History of Chemistry

Although chemistry is widely considered among its practitioners to be a modern science, technological processes based on chemical reactions have been in standard use from the distant past. The production of salts, dyes and paints, cosmetics, and fermented beverages made use of techniques and reactions common to chemical experimentation (such as filtration, dissolution, and sublimation). Among these early crafts, metallurgy involved a widening knowledge of metals and their alloys, and entailed the recognition of certain stones as metallic ores. However, these activities seem to represent only a practical, applied use of chemical processes. Although craft-workers may have developed their own concepts regarding the substances involved in a given process, records of such ideas have not come down to us, and the discoveries and improvements they made seem to have been based largely on a trial-and-error approach. The ancient considerations on the nature of matter that have come down to us were composed by philosophers who considered the problem of change. In attempting to understand the objects of the natural world and the changes these objects undergo, the idea of earth, air, fire, and water as material elements was first postulated by the Greek natural philosopher Empedocles (492ñ432 BC), and was brought into its most well known form by Aristotle (384ñ322 BC). Analogous theories appeared around the same time in China (fire, earth, water, metal, and wood) and India (earth, water, fire, air, and space). Western alchemy appears to have arisen in Hellenistic Egypt and the Near East during the last couple of centuries BC, in conjunction with several mystical sects and the increasingly common craft practices of creating imitation precious stones and metals. Although it lacked the logical rigor of earlier Greek philosophies, alchemy nonetheless attempted to engage the complex world of chemical processes and mineral substances in a scientific way, which eventually led to ideas involving the transmutation of base metals into precious ones and the preparation of a substance for extending the human life-span. The term protochemistry is often used to refer to some of these activities, and it is this aspect of alchemical activity with which the present work is concerned. Many chemical and mineral substances known to the ancients were of great importance to civilization. The most ancient literary evidence of familiarity with such substances is from Sumero-Assyrian dictionaries that include some chemical terms. By the time of the rule of the Assyrian king Assurbanipal (668ñ626 BC), these lists of chemical terms included several kinds of common salt (NaCl), gypsum (CaSO4 . 2 H2O), and substances recognized today as metallic sulfates and sulfides. In ancient Egypt an impure form of sodium carbonate was particularly important in mummification. The discovery of gunpowder in China around the ninth century AD led to an increased interest in saltpeter (KNO3). Other substances were recognized to have remarkable physical properties, such as the easily sublimated sal ammoniac (NH4Cl). The extraction of elemental mercury from cinnabar (HgS) seems to have become common practice by the end of the fourth century BC. The earliest extant description of this process is in the treatise On Stones by Theophrastus (c. 372 ñ c. 287 BC), while the laboratory synthesis of cinnabar by combining and then subliming mercury and sulfur seems to have been known before AD 400. A group of mineral substances that probably attracted attention due to their often striking blue and green crystals and their distinctive chemical properties were the sulfates of divalent metals (principally of iron and copper), commonly known in early terminology as atrament and vitriol (the latter of which will be used in this paper). In this paper we will attempt to trace the history of vitriol as revealed in chemical literature from antiquity to the early modern period, and discuss some examples of its uses and opinions about its nature and effects. The mineral substances referred to here as vitriol are recognized in modern science as hydrated sulfates of iron, copper, and even magnesium and zinc, all of which form as secondary minerals within the weathering zones of metallic sulfide deposits. These sulfides were generally referred to as ìpyritesî during antiquity. Use of this term became more restricted by the sixteenth century to refer mostly to sulfides of metallic luster which yield little or no metal, although more minerals than the one currently called pyrite were still included under this term. The name marcasite was used by the Arabs in referring to these same minerals, and became used synonymously with pyrites in much of the literature of the sixteenth Chem. Listy 96, 997 ñ 1005 (2002) Refer·ty