Comparison of electronic structure and hydrophoby of different tautomers of 1-alkyl-3-methyl-2-pyrazoline-5-ons (AMP) and 1-phenyl-3-methyl-2-pyrazoline-5-ons (PhMP) has been carried out. Replacement of phenyl radical by alkyl radical (C₄ - C₇) increase the hydrophoby of the substances and electronic density on oxygen donor atom of carbonyl group resulting in an increase of alkyl derivatives effectiveness in the metal ions extraction.

Distribution of AMP between aqueous and chloroform phases in relation to the concentration of aqueous solution of trichloracetic acid (TCAA).

From 0,5 M concentration of TCAA the reagents are completely protonated in organic phase, superstoichiometric extraction of TCAA is evident in more concentrated solution. Mercury (II), indium (III), scandium (III), zirconium (IV), hafnium (IV), thorium (IV), iron (III) are extracted by AMP from trichloracetic solutions to chloroform. The effectiveness of the extraction increases with increasing length of hydrocarbon radical. Isotherm of the triple system water - 1-hexyl-3-methyl-2-pyrasoline-5-on - trichloracetic acid solubility at 293 K has been built. Five fields are located in the concentration triangle, including the field of two-phase liquid equilibrium. The field of stratification is retained on addition of inorganic acids.

Investigations of extraction of elements in aqueous stratifying system without organic solvent show appreciable analogy between this system and traditional system with chloroform as an organic solvent in the distribution of elements.

It is advised to use extraction systems with single liquid component - water, because they significantly raise safety of the process.