Early theories of combustion and calcination

Robert Boyle (1627-1691) was one of the pioneering chemists of this era. A major problem that occupied his interest was elucidating what really constituted an element. He showed through experimentation that the four elements of Aristotle and the three principles of the alchemists (mercury, sulfur, and salt) did not deserve to be called elements or principles at all, since none of them could be extracted from bodies, e.g., metals. He defined an element as follows  

He believed in the atomic theory, which he used to explain chemical changes. In 1662, he discovered the law that hears his name, Boyle s law (the volume of a gas is inversely proportional to the pressure).  

Robert Hooke (1635-1702) postulated a theory of combustion involving twelve propositions in which he stated, among other things  

Sceptical Chymist or Chymico Physical Doubts Paradoxes, Touching the Spagyrist s Principles commonly call d Hypostatical as they are wont to be Propos d and Defended by the Generality of Alchymists, p. 350, London (1661). 

John Mayow (1641-1679) recognized that combustion and respiration are analogous processes. He correctly stated that animal heat is developed in the muscles, and proved that arterial hlood in a vacuum gives off a gas.  

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