[en] The on-line separation of Hf and Ta produced by the reactions of ¹⁶³Dy(¹²C, xn) Hf and ¹⁶⁵Ho(¹²C, xn) Ta respectively have been carried out and the separating conditions have been discussed. From the experimental results one can see that it is possible to separate elements 104 and 105 with a similar thermochromatographic method