text: 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.\n\nI 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.