when dissolving powders in water?

Question

After water can not disolve any more of a powder and even more of a different powder is added is first powder added the only thing disolved in the water or is it a mix of them.

Answer 1

For all practical purposes, if a solution is saturated (can not dissolve any more) it is full and all others will fall to the bottom, undissolved.

Realistically a small (very small) amount of the other powder could dissolve if it had different enough properties.