I will be using 10ml of phosphate liquid, bromocresol green .1% indicator and titrating with sulfuric acid. im thinking they are wanting 0.1N sulfuric acid and its just written wrong. they have it written as n10 and I think that is what is throwing me off. we are testing for free acid, that is why i was asking about free acid. the link you gave me helped me alot, thanks for that. I understand now why we are testing for free acid.