Question

How can I separate Na3PO4 and NaH2PO4 that are in solution. Can use normal re crystalization because they are to similar and both are soluble in the same solvents.

Thanks

Answer 1

You cannot separate them because they can easily turn one to another. Really, if you mix equal amounts of Na3PO4 and NaH2PO4 in the solution, you will obtain the solution of Na2HPO4.
If you need to obtain both substances from the solution, you can convert them into one by adding the phosphoric acid H3PO4 or sodium hydroxide. Then you take part from the obtained solution and proceed the reverse operation.