As every child knows, wood burns.  Well unless it's damp. But even then, if the fire is hot enough it'll still eventually catch fire. Sooner or later, however, everything eventually burns out, leaving ashes and residue behind.  In the 17th century Johann Joachim Becher, who may or may not have gone by the name "JJ", came up with a theory as to why this should be.  He was an educated and talented man and certainly open to scientific debate being in his life time a physician, a scholar and something of an adventurer in his travels across Europe.  But it was his work with alchemy – a proto-science that was a precursor of modern chemistry – for which he would be remembered in later years.

Commenting on the burning of objects and how they became ash or, at the very least, lighter than they were when they were burned, JJ came to propose the theory that there was a common element in all combustible objects that, upon burning, would be released.  This fire based element would react with the air and leave behind the residue.  Crucially, however, an object didn't have to be burnt, for rust was also explained as the effect of the element leaving the object into the air.

Like any aspiring great scientist, Bercher knew his discovery required a Greek name in order to ensure it was taken seriously by the learned men of Europe.  For this reason he turned the Greek word flame or Phlox, and more specifically Phlogiston which translated meant "burning up", to name his theory.  It can be presumed thus that following this discovery toasts were drunk and many scholars and academics patted themselves on the back and saluted this bold new step for knowledge.

The only problem of-course was the Berchers Phlogiston theory was, as might be expected from its appearing here, hopelessly wrong.  Experiments by other alchemists and scholars began to turn out results that contradicted the idea of the Phlogiston being released.  For example the burning of magnesium would return magnesium oxide, a compound that was actually heavier than its former pure state.  Apologists came up with their own theories as to why this should be.  Some proposed that Phlogiston had negative mass or was lighter than air, but none of these could explain the anomalies in the results.

By the late 18^th century, work by Antoine Lavoisier, regarded as the father of modern chemistry, and others had conclusively put this theory to rest.  To replace it, the scientists of the age proposed the Caloric Theory which proposed that heat was not a substance inside objects but rather a self-repellent liquid that flowed from hot to cold and could permeate solid objects.  Hence mass would flow away from warmer objects such as wood when burnt, and would return to colder ones, like metals, as they cooled explaining the discrepancies.

This still was not right. It would take another century for the discipline we know as thermo-dynamics today to become properly established.  Though Phlogiston theory was well and truly debunked, it represents even today a key scientific virtue.  That of being ready to embrace a theory, put it to the test and, most importantly of all, to be prepared to move on to new theories when evidence proves otherwise. 

That willingness to embrace facts is at the core of all scientific enquiry. While it can be tempting in this series to look back at the men and women mentioned in these articles and laugh at their beliefs, it’s important to remember that each idea was a step in the process of learning about our world and about ourselves.  This willingness to educate ourselves and ask questions has brought us to where we are today and is what will lead us into tomorrow if we will only but dare to learn.