Soap (and some other things one cannot easily make explosives out of)

by Lucas Wilkins

Following in the footsteps of the first post on this blog, I though I would point out another popular misconception: You cannot make explosives out of soap – despite this process being crucial to the plot of “The Legend of Zoro”. I’ve heard this myth in various forms over the past year, usually it is soap, but I have also heard that one can make explosives from biofuel. It is essentially the same issue in both cases. I guess this myth irks me in particular because it is a misunderstanding of one of the most simple and widespread chemical reactions there is.

So, making soap is pretty easy, it is the same principle as an acid/base reaction. Just mix some fat and some inorganic base (say sodium or potassium hydroxide) and the metal ions displace the glycerol in the fat giving soap and glycerol (glycerin).

How to make soap. From Wikipedia: Saponification - Fat (left), Base (on arrow), Soap (inner right), Glycerol (far right)

Some more detail…

Fats are tri-glycer-ides which means “three bits stuck to a glycerol molecule”. The saponification processes is the breaking off of these three bits (the fatty acids), which become the soap (fatty acid salts), leaving glycerol. As a word equation:

Fat + Base \rightarrow Soap + Glycerol

or, in the very similar case of (base catalyzed) biodiesel production. In this case there is a load of methanol (MeOH) not base (NaOH, KOH):

Fat + Methanol \rightarrow Biodiesel + Glycerol

It is fairly easy (though very dangerous) to make an explosive (nitroglycerin) from the glycerol byproduct by nitration, this is undoubtedly where the myth comes from. But somehow the understanding of this reaction has reached the masses as “you can make a bomb out of soap/biofuel” – which you can’t: You can make a (shit – if you like your limbs) bomb out of a byproduct of soap production.

End Of Rant.

4 Comments to “Soap (and some other things one cannot easily make explosives out of)”

  1. Just noticed on the site stats the 2nd and 3rd top searches leading to this site are:

    “how to make glycerin from soap”

    “simplest way to manufacture glycerin”

  2. If recall the forensic evidence that the Birmingham Six were convicted on, and which was later overturned leading to their release, revolved around a test of residue on their hands. The expert witness suggested it concluded they had been handling bomb-making materials, but it was later shown that soap could give the same result. I don’t know the details in any depth, it likely relies on chemicals not dissimilar to that you discuss above. That was the first time I saw the two compounds linked in such a tragic way.

    • According to the appeal judgment, it seems that they rejected the Griess test (link)on the basis that it was unreliable (which it is), as well as the fact that when the samples were taken to the lab “With one exception, the subsequent tests all proved negative.”

      This wasn’t the only reason they were released, it was also because it was demonstrated that the police beat confessions out of them and lied about it – police corruption will always change peoples minds.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s


Get every new post delivered to your Inbox.

Join 483 other followers

%d bloggers like this: