First performed in 1610, Jonson's satire of human materialism was set in then contemporary London. There are therefore a great many characters and themes which the original audience would have recognised (probably with some discomfort, as very good satire is apt to produce.) Audiences would have been entirely familiar with:
1. The Plague. Attempts at control of this periodic epidemic meant that theatres in London were frequently closed during periods of high infection, and the play's first performance is recorded as taking place in Oxford in September 1610, when the London theatres had been closed since July. Everyone would have recognised the setting of The Alchemist: a city hit by plague restrictions regarding crowds and public gatherings, and from which everyone who could afford to move away did. That left the poor, and those whose businesses would have been robbed had they left them. Lovewit is a gentleman who has gone to the country, but his servants decide to remain in Town, risking infection in order to capitalise.
2. Social Mobility. This new Jacobean age had become very aware of the possibility of making money, and the social implication of successful trade and enterprise enabling the crossing of social divides which not long before had been regarded as insurmountable.The 'gulls' - the dupes who believe that they can get rich quick by magic - are also risking their lives, and are portrayed across the social spectrum: from the Knight to the failing tobacconist. Nobody is immune to greed and acquisition, but the Spaniard (impersonated by Surly) was a popular post-Reformation hate-figure, as were Puritans (represented here by the Anabaptists, an extreme Protestant sect who practised a sort of proto-communism) and who were notoriously anti-theatre. Within the context of the satire, the literal 'making' of money is the pivotal point, hence
3. Alchemy. With its ancient roots in Hellenistic Egypt, historically alchemy was the scientific/philosophical search for a Universal Panacea (to eradicate disease), Elixir of Life, (to discover the secret of immortality) and the fabled 'Philosopher's Stone', which was supposed to have the power to turn base metals into gold. It is this last that concerns the 'alchemists' of Jonson's play. Alchemy was perceived ambivalently by the early 17th Century - variously as devilry, as merely crackpot, and a belief among some that there might be something in it. All attitudes are represented in the play. (Think of the way we regard astrology now, still...) Certainly, the Elizabethan age had seen a significant rise in con-artists, and these would have been highly familiar to the sophisticated London audience in 1610. However, alchemy had begun to merge with actual early chemical research with the emergence of actual experimental scientists such as the philospher-chemist Paracelsus (c.1493-1541) who pioneered the use of minerals in medicine. A bit like a similar merging of 'astrology' and 'astronomy' in the same age, the boundaries between science and magic were inevitably blurred. It is therefore entirely plausible that the 'gulls' are taken in by a (formula?) of science and magic, and Subtle can play on his victims' particular prejudices, so that a delicate scientific process or an arcane magic spell could be wrecked by being observed. Thus for his gulls, the main business takes place in another room (giving scope for quackery) just as for the audience (placed in the same position) it takes place off-stage.