AbstractSal icylaldehyde n-alkanohydrazones (SAAH or H₂L) having 1 to 13 carbon atoms in their alkyl chains were synthesized and used for the extraction of some lanthanoid ions (Ln³⁺) including praseodymium, europium and ytterbium ions from aqueous solutions containing both tri-n-butyIphosphate (TBP) and perchlorate into I,2-dichloroethane The extracted species were (Ln³⁺) (HL-)₂(TBP)₃(C10₁,-) for all SAAH. The partition coefficients, Kd, of SAAH increased with an increase in the carbon number of the alkyl chain, the increment of log Kb being 0.64 per a carbon atom. The acid dissociation constants of SAAH also increased slightly with an increase in the carbon number, but the extraction constants of their lanthanoid complexes were almost independent of the length of the alkyl chain.