Is common salt soluble in all types of water?
Most types of water do so; save for the kind that is already saturated with salt.
When we write
It is worthwhile at home to grow macroscopic crystals of salt. Take a saturated solution (a solution that is in equilibrium with undissolved salt), filter it, and add (precisely) 1 tiny crystal of salt. If evaporation is kept to a minimum (by covering the solution), aqueous salt will precipitate only on the 1 salt crystal that you added. I have grown very large crystals (