[Ragoza]

Say 1-phenylethylamine with mesotartaric acid? I understand if I had a chiral agent I could get diastereomeric salts, but what, if anything, will form if I use an achiral agent?

If a salt does indeed form, wouldn't it still be diastereomeric? A mix of (R)-amine-(R,S)-acid and (S)-amine-(R,S)-acid compounds?

[renge ishyo]

You would get a racemic mixture of products. Yes, some products will be of one isomer and some will be of the other isomer, but overall in solution you will have equal numbers of each (a 50:50 mixture).

[a student]

achiral agent won't be able to realize the difference of these two enantiomers

[movies]

Actually, this particular example will be a bit more complicated because you are dealing with a diacid and therefore the stoichiometry would lead to a 2:1 salt of the amine and acid.  If you think of the two acid/base reactions occurring in sequence, the first equivalent of amine to react with the acid would lead to a chiral product (composed of two chiral materials since the acid would then be desymmetrized into an acid-carboxylate).  Thereafter you could see some preference in the second acid/base step leading to a non-equal distribution of (R)(R), (R)(S), and (S)(S) acid salts.