As anticipated from preliminary test tube experiments, the fractions are all giving nice, primrose-yellow precipitates on addition of citric acid saturated BuOAc (CASBA!). On aggregation the precipitate appears more orange, although this could be a yellow harmala gunk that has coagulated. The precipitate is very fine at the moment and takes quite some time to settle.

Because the most concentrated fraction was also the largest (150mL), I'll be testing 25mL portions of it with a number of different methods. CASBA was of course quite effective, but the precipitate is always very fine. Next up, medium-coarse (from the packet) citric acid crystals; to be followed by finely ground CA. Also available are tartaric, malic, and fumaric acids but I'd like to get hold of some succinic acid too if at all possible. I'm hoping at least one of these options gives a result which settles more quickly.

One thought on why, in the earlier tests, the precipitate turned pink and then went back to yellow: it could be that the particles became coated with a reddish impurity that is insoluble below about 16°C but which redissolves when the temperature rises again. Or there is a phase transition between different crystal forms at this temperature. This seems to have been mirrored in the reports of a similar colour change upon refrigeration of the EA precipitate.

Does this colour change reverse on warming if the precipitate is kept in contact with the EA solution? What happens when the precipitate is filtered off cold then allowed to warm up once dry? And what happens if the precipitate is cooled with a portion of fresh EA?