Editing Fatty acid (section)

===Acid-base reactions===
Fatty acids do not show a great variation in their acidities, as indicated by their respective [[Acid dissociation constant|p''K''<sub>a</sub>]]. [[Nonanoic acid]], for example, has a p''K''{{sub|a}} of 4.96, being only slightly weaker than acetic acid (4.76). As the chain length increases, the solubility of the fatty acids in water decreases, so that the longer-chain fatty acids have minimal effect on the [[pH]] of an aqueous solution. Near neutral pH, fatty acids exist at their conjugate bases, i.e. oleate, etc.

Solutions of fatty acids in [[ethanol]] can be [[titration|titrated]] with [[sodium hydroxide]] solution using [[phenolphthalein]] as an indicator. This analysis is used to determine the free fatty acid content of fats; i.e., the proportion of the triglycerides that have been [[hydrolysis|hydrolyze]]d.

Neutralization of fatty acids, like [[saponification]], is a widely practiced route to [[metallic soap]]s.<ref>{{Ullmann |last1=Schumann |first1=Klaus |last2=Siekmann |first2=Kurt |year=2000 |doi=10.1002/14356007.a24_247 |title=Soaps}}</ref>