The fourth test was performed with addition of methanol to
form an extraction mixture with the ammonium hydroxide solution
in a ratio of 1:1 (MeOH:NH4OH (aq)). With this solution the
separation between the supernatant and the precipitate increased
considerably compared to the second test. Therefore, it was
decided to perform a fourth test, increasing the proportion of
organic solvent to 8:2 (MeOH:NH4OH (aq)), which then yielded a
much clearer supernatant and totally precipitated solid material.