Dihcptyldithiophosphoric acid was prepared from the reaction of phosphorus pentasul- fide with heptanol and purified with lime slurry. The solvent cxtraction of Ni(II), Cu(II), Co(II), and Zn(II) metal ions as diheptyldithiophosphates from aqueous Solutions into an organic phase, and the possibility of their separation from one another have been investigated.