can someone tell me the basis for this formula

FFA% = 0.546 x t for titration with 1g KOH per litre

When there is a 1:1 ratio of FFA to KOH?

RCOOH (FFA) + KOH ---> RCOO-K+ + H2O

and can someone explain the basis for saying that the acid value is equivalent to (1/2)FFA percentage by weight?

I think the formula you are talking about came from Kenito Oko's method, right? I think HE would be about the only guy who could answer, as I don't understand what all he does in that method either!

Only thing I can think of is b/c titration determines acidity, and FFA's are not the only acids in the sample (triglycerides break down with water into FFA's and glycerin), glycerin has acidity to it. But still, assuming FFA is half the total value seems somewhat inaccurate to me...there's got to be a more accurate method.

???
confused

I'd suggest it's to allow calculation of v/v% or w/w% FFA from the number of moles of FFA (given by the titration). I'm not sure if it's valid or not, as it would depend on the specific FFA composition.

Not sure where the acid value comment has come from.