How much does smoke weigh?

Marilyn is Wrong Copyright © 2001-2005 1995-1998 Herb Weiner. All rights reserved.

Ask Marilyn ® by Marilyn vos Savant is a column in Parade Magazine, published by PARADE, 711 Third Avenue, New York, NY 10017, USA. According to Parade, Marilyn vos Savant is listed in the "Guinness Book of World Records Hall of Fame" for "Highest IQ."

In her Parade Magazine column of February 15, 2004, Marilyn claims that if only 15 pounds of ashes remain after burning 100 pounds of logs, 85 pounds of smoke (containing particulate matter and gases) and water vapor go up the chimney.

Sorry Marilyn

Sorry Marilyn, but you forgot to account for the oxygen consumed by the fire, which combines with the carbon and hydrogen in the wood to form carbon dioxide, carbon monoxide, and water vapor. (Other oxides, such as oxides of nitrogen, may also be formed.) What is Smoke?

T. Wade Gonder twgonder@sbcglobal.net wrote:

My understanding is that the elements you listed are considered part of the smoke, since it is the hydrocarbon "smoke" that combines with oxygen to create the chemical reaction we call fire. Technically the oxygen is consumed, rather combined with other elements. One could get picky and try to differentiate soot from smoke, but that misses the point of her simple explanation.

A lot of confusion exists with the terms vapor, smoke and soot. Smoke is an imperfect term. The question is imperfect because of the term smoke. Some oxygen may combine with other impurities (e.g. oxides of nitrogen), but generally we don't consider the oxygen byproducts part of the smoke (or soot) nor do we consider the other impurities. The smoke (hydrocarbon vapor) is what reacts with oxygen, it is then no longer smoke.

The following definitions of smoke are from Webster's Third New International Dictionary (Unabridged):

1 a (1) : the gaseous products of burning carbonaceous materials made visible by the presence of small particles of carbon (2) : a similar incompletely burned volatilized product resulting from incomplete combustion and finally settling as soot -- compare FLAME

Based upon the above two definitions, there is certainly some ambiguity regarding the definition of the term "smoke". The first definition clearly includes everything that goes up the chimney. However, Marilyn would still be incorrect if we use the second definition of smoke, since at least a portion of the wood is completely combusted, producing carbon dioxide. Using the second definition, this completely oxidized carbon would not be included in the 85 pounds of smoke and water vapor.

http://www.wiskit.com/marilyn/smoke.html last updated December 25, 2005 by herbw@wiskit.com

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