[GoldShadow]

Recently I performed a simple experiment, extracting fat from commercial potato chip brands. We used dichloromethane as solvent to dissolve the fat and extract it by distillation.

However I don't really understand why dichloromethane is a good solvent for fat/lipids. Dichloromethane is CH₂Cl₂, which means it has a tetrahedral structure right? This means it must be polar.  But fats/lipids are nonpolar.  Why then does dichloromethane dissolve lipids?

edit: Well I decided to look at the electronegativities for each of the atoms involved... is it because the differences in electronegativity in the C-Cl and C-H bonds is not great enough to make it a significantly polar molecule?

[Dan]

Yes, while DCM does indeed have a dipole moment, it is not a large one, and has a relatively (eg to water) low polarity.

You may find this interesting http://en.wikipedia.org/wiki/Solvent#Properties_table_of_common_solvents

[ARGOS++]

Dear Dan,

At ?our? times, we had to learn the old wisdom of Alchemists called:
                               “Similia Similibus Solvuntur”
- and I’m sure they were already trained in a ‘similar’ Way.

Translated to “New-German”:
                               “like dissolves like”        (I was able to find.)
But probably a little more correct:
                               “like dissolves similar”

Today, most believe that polarity is sufficient enough to be the cause for.
I’m still believe, there are others too, like the molecule-size (in Chemistry sense), and/or ….

But CH₂Cl₂ is by Definition NOT very polar at all, as the angel build by Cl-C-Cl is significant larger as
the regular 109° angel of the ideal Tetrahedron.
(Maybe somebody knows/spends the exact value.)

Quintessence: 
The centres of contrary Charge are much closer together as most think, with the result of a very “week” polarity, quite close to CCl₄, the incarnation of NON-Polarity.
(“closer together”: in relation to what?)
That’s precisely the cause, why you have to replace the very poison, carcinogen CCl₄ with “your” CH₂Cl₂, because its quite: - smaller danger and  - very similar qualities, where ever possible!

Good Luck!
                    ARGOS⁺⁺