MadSci Network: Chemistry

Re: How does baking soda absorb odors?

Date: Sun Aug 30 23:54:30 1998
Posted By: Michael Weibel, Grad student Chemistry/Physics, University of Utah
Area of science: Chemistry
ID: 903895026.Ch

Hi Hugh.  Funny you should ask this question, as it's one that I was just 
thinking about recently.  The answer is surprisingly simple.

You might already know that an "acid" may be thought of as a compound that 
can give up a H+ (a proton donor) and a "base" is one that accepts a 
proton.  The combination of acid and base always results in the formation 
of water and a "salt".  This salt is the molecule made from the "leftover" 
fragments in the reaction.  For example, if you mixed hydrochloric acid and 
sodium hydroxide, the reaction occuring would be:

             HCl + NaOH ---> NaCl + H2O

(this is a simplified picture of the reaction, since it is actually the H+ 
and OH- that react and the other fragments stay separated in solution.)

Baking soda is a weak base chemical called sodium bicarbonate (NaHCO3).  It 
will react with an acid to form H2O and a salt.  It turns out that many 
odors are caused by organic (carbon containing) acids.  One example is 
butyric acid, which is the nasty smell you get from rancid butter.  As 
such, these molecules can react with the bicarbonate to form a non-smelly 
salt and water.  

Additionally, odors can come from molecules called esters.  I expect that 
these behave somewhat like acids, and will be neutralized in the same 

I hope that I have answered your question.  Please feel free to email me 
at: if I can be of any further assistance.

Best Regards,
Mike Weibel

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