Your choice (acidic) is

• Note that there are extra protons (H⁺) in the solution.
• Note also that sodium chloride, (NaCl), a bi-product of the reaction, is dissolved in the aqueous solution while the 2-naphthol* has oiled out* of the solution.

Now you need to collect the crude 2-naphthol that has not crystallized, but oiled out.

What technique will you use?