At first I wasn't sure if this is good enough for new topic or just for short question thread,
but since it's part of bigger total synth. that isn't on this forum I will make it a thread,it might
expand on rest of the synth. and become more helpfull for others!

So...
Once you got/made some o-toluidine getting mathaqualone sounds very easy.
I understand chemistry behind most steps but not this one:

Making N-acetyl-anthranilic acid (NAAA) from N-acetyl-o-toluidine (NAOT)

Can someone explain me mechanism of this synthesis and purpose of MgSO4 in it!?
It definitely isn't drying agent if reaction is done in aqueous solution!
I also think that reflux might be much better option than open pot reaction,pleas correct me if I am wrong.

Why is NAAA insoluble in acid and soluble in basic aqueous solution isn't quite clear to me,
It reminds me on A/B extraction where A form is insoluble in water and B form is.
What is recommended concentrations of "diluted NaOH" in this kind of reaction
and can it be added to post reaction mix to increase solubility and prevent premature
crystallization if filtration of large volume of hot liquid presents a problem at the moment!?
(Since NaOH won't react with MnO2 and it won't mind if it reacts with AcOH formed from EtOH I don't see reason against!)
I think that measuring pH might be more practical to determine if there is any NAAA left
or does it need some more acid to crash out while keeping it high enough to prevent any
undesired reaction,if there are any.
Does anyones know how to get/calculate that pH,based on what parameters!?

Presumably, the MgSO4 is a pH buffer.

NAAA precipitates on adding acid because it is an acid.

"Weak NaOH" means maybe 10% or so. It's not that important. Just acidify the well-filtered solution and then filter the precipitate and wash it with water. There doesn't seem much point in reprecipitating.

Note that cheapskate lifted his procedure from 'The laboratory preparation of a simple vitamin: p-aminobenzoic acid' by Chester B. Kremer, J. Chem. Educ., 1956, 33 (2), p 71. They use a closed vessel under mechanical stirring in a steam bath.