Phlogiston

Phlogiston (from the Ancient Greek φλογιστόν phlogistón "burning up") was a fire-like element contained within combustible bodies and released during combustion. The air was thought to have a limited capacity to absorb the phlogiston released, this being the reason why combustion did not take place for long in an enclosed container.

The theory was first postulated in 1667 by Johann Joachim Becher as an attempt to explain processes of burning such as combustion, metabolism, and the rusting of metals, which are now collectively known as oxidation.

During the eighteenth century, as it became clear that metals gained weight when they burned or were oxidized, even though they were supposed to have lost phlogiston. The threory remained dominant until Antoine-Laurent Lavoisier (1743 – 1794) showed that combustion requires a gas that has weight (oxygen) and could be measured by means of weighing closed vessels.

Theosophical use

Well, we believe in the much laughed at phlogiston (see article “What is force and what is matter?” Theosophist, September), and in what some natural philosophers would call nisus, the incessant though perfectly imperceptible (to the ordinary senses) motion or efforts one body is making on another — the pulsations of inert matter — its life. The bodies of the Planetary spirits are formed of that which Priestley and others called Phlogiston and for which we have another name — this essence in its highest seventh state forming that matter of which the organisms of the highest and purest Dhyans are composed, and in its lowest or densest form (so impalpable yet that science calls it energy and force) serving as a cover to the Planetaries of the 1st or lowest degree.