The key is Hendersson Hasselbalch equation.
Check this.

 What quantity (moles) of NaOH must be added to 1.0 L of 
2.0 M HC2H3O2 to produce a solution buffered at each pH?
 a. pH = pKa
 b. pH = 4.00
 c. pH = 5.00

I don't understand how to solve this. I started by finding the value of the ph for the then finding the pOH and then finding the concentration of the pOH but this answer seem to be wrong. I check the manual answers and my answer doesn't match. I think I'm supposed  to assume that the concentration for the acid and the conjugate base is the same and that they add up to be 2M as suggested in the problem therefore the conjugate base would be 1, since there's a 1:1 molar ratio OH would have the same concentration and the same amount of moles. I just don't understand why the first procedure that I used doesn't work and I also don't understand why the acid and the conjugate base should be equal to 2 since this is the concentration given for only the acid ??

Thank you

There is two routes I can take

The classic route in making a gold sulpho-resinate (Gold Salt + Sulphured resin)

Or the more modern route gold aryl mercaptide (Gold Salt + ethyl acetate + dimethylbenzenethiols + Polymer)

But I would prefer to work with more natural products

Thank you very much for the help Hunter, I will read up on fractional crystallisation.

I use gold chloride on pottery. This is mixed with an organic binder & flux. But I find the shelf life is short, the gold seems to revert back to metallic Au after a couple of weeks. So I am looking at a more stable salt of gold for longer storage.

Even if I dry it? I have successfully dried AuCl4 to powder it using a vacuum chamber and low heat?