text: the ph of ol oleic and capylic acid? does any one know why when adding sodium hydroxide to a 50/50 solution of oleic and capylic acid the ph drops at first and then slowly rises??? both oleic and caprylic acid are long chain fatty acids - measurement of ph will be inaccurate as very little of either acid will actually dissolve in water and neither acid readily dissociates.  i would have thought that you may have seen an initial rise in ph, followed by a slow fall, rather than the other way around. this would make sense as the reaction between oleic/caprylic and sodium hydroxide is not particularly fast.