The philosopher's stone Alchemy is defined by the Hermetic quest for the philosopher's stone, the study of which is steeped in symbolic mysticism, and differs greatly from modern science. Alchemists toiled to make transformations on an esoteric (spiritual) and/or exoteric (practical) level. It was the protoscientific, exoteric aspects of alchemy that contributed heavily to the evolution of chemistry in Greco-Roman Egypt, in the Islamic Golden Age, and then in Europe. Alchemy and chemistry share an interest in the composition and properties of matter, and until the 18th century they were not separate disciplines. The term chymistry has been used to describe the blend of alchemy and chemistry that existed before that time. During the Renaissance, exoteric alchemy remained popular in the form of Paracelsian iatrochemistry, while spiritual alchemy flourished, realigned to its Platonic, Hermetic, and Gnostic roots. Consequently, the symbolic quest for the philosopher's stone was not superseded by scientific advances, and was still the domain of respected scientists and doctors until the early 18th century. Early modern alchemists who are renowned for their scientific contributions include Jan Baptist van Helmont, Robert Boyle, and Isaac Newton. Alchemy in the Islamic world In the Islamic World, the Muslims were translating the works of ancient Greek and Hellenistic philosophers into Arabic and were experimenting with scientific ideas. The Arabic works attributed to the 8th-century alchemist Jābir ibn Hayyān introduced a systematic classification of chemical substances, and provided instructions for deriving an inorganic compound (sal ammoniac or ammonium chloride) from organic substances (such as plants, blood, and hair) by chemical means. Some Arabic Jabirian works (e.g., the "Book of Mercy", and the "Book of Seventy") were later translated into Latin under the Latinized name "Geber", and in 13th-century Europe an anonymous writer, usually referred to as pseudo-Geber, started to produce alchemical and metallurgical writings under this name. Later influential Muslim philosophers, such as Abū al-Rayhān al-Bīrūnī and Avicenna disputed the theories of alchemy, particularly the theory of the transmutation of metals. Problems encountered with alchemy There were several problems with alchemy, as seen from today's standpoint. There was no systematic naming scheme for new compounds, and the language was esoteric and vague to the point that the terminologies meant different things to different people. In fact, according to The Fontana History of Chemistry (Brock, 1992): The language of alchemy soon developed an arcane and secretive technical vocabulary designed to conceal information from the