[horizontm]

Is there a way to make the potassium ion in potassium nitrate into an insoluble compound. I need to find a way to separate K+ from a mixture of nitrate, and the only way to do that is to make an insoluble compound.

The exact question is "design a scheme to separate a mixture of the four cations, Ag+, K+, Ca2+, Al3+, each in a compound with nitrate"

I found the other three but can't crack it for K. Help?

[AWK]

There are two salts of K sparingly soluble in water, namely KClO4 and K2PtCl6

[Borek]

If you have removed others, aren't you left with just K? Won't it be enough to dry out the solution?