[jazzy]

I have a solution (6 lit) with pH=8.5. How much 50% sulfuric acid must I add to correct the pH to 2,8? How much is the pH of 50% sulfuric acid. It is negative pH, right? (graph dependence of pH=f(w/w) sulfuric acid)

thanks!

[Borek]

Not enough information to solve. As long as you don't know why pH is 8.5, you can't calculate amount of acid necessary to neutralize the base. If it is strong base - no problem, if it is weak - everything is possible.

50% w/w sulfuric acid pH is negative, but don't ask about details. It is too concentrated solution for calculations.

[jazzy]

Everything I know is that pH needs to be 8,5 (adjusted with NH4OH, I think) in order for the enzymic reaction to take place in the continuous reactor. Changeing the pH to 2,8 is needed for precipitation of the amino acid. I thought, that, if I know the pH of 50% sulfuric acid, I would find how much (lit) H2SO4 I have to add to the solution (so it can reach the concentration of H+ at 2,8 pH).
Can it be that simple???

[Borek]

Can it be that simple???

No. You need to know - at least concentration of ammonia used. But I suppose it ewas not ammonia, but ammonia buffer. Then there is the aminoacid part - it has to be protonated. I think it can be much easier to add acid measuring pH then calculate its amount.