The phenol-containing fractions of ether-soluble substances of black kraft liquor obtained in laboratory scale pulping of spruce was studied by GPC using gel Sephadex G-25 and dimethylsulphoxide as elluent. The studies showed that the mixtures of aromatic compounds with MM up to 1.000 exhibit polyelectrolyte properties. For the suppressing the electrolyte behaviour, lithium bromide and orthophosphoric acid (0.03 mole/l each) should be introduced into the elluent.