Definition of "phlogiston" [phlo•gis•ton]

• A hypothetical substance formerly thought to be a volatile constituent of all combustible substances, released as flame in combustion. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "We decline entering into a minute examination of his experiments, as few of his recitals of them are free from the triune mystery of phlogiston, which exceeds the utmost stretch of our faith; for according to it, carbon is phlogiston, and hydrogen is phlogiston, and azote is phlogiston; and yet there are not three phlogistons, but one phlogiston!"
• "Yet it may not be altogether amiss to reflect that the physicist of to-day is no more certain of his ether than was his predecessor of the eighteenth century of the existence of certain alleged substances which he called phlogiston, caloric, corpuscles of light, and magnetic and electric fluids."
• "With precipitated indigo, the orpiment doesn't create changes, Bergman continued, because the union of phlogiston is too strong — you need the heat and the alkali to relax it."