Where 𝐾 𝐸 is the equilibrium complexation constant. When the value of z is greater than 0.5 then (2:1) acid-amine complex is formed in the organic phase. And is defined as [19] , When the graph was plotted z/(1-z) vs. weight of acid in aqueous phase it gives the value of equilibrium complexation constant. Figure . shows equilibrium complexation constants for extraction of succinic acid using TOA in the different diluents. The mixture of TOA in benzyl alcohol gives the highest 𝐾 𝐸 value was 572 kg/mol. The highest 𝐾 𝐸 value for TOA in 2-octanol and 1-decanol was 65 and 58 respectively.