the key to hydration is the salt. you are right in that this is rally the first and best medicine you get in the hospital. it is what saves your life, if you can survive the rest of the crap they do to you!
i suppose boiling water with silver in it would be ok in an emergency, but making electro silver from anything but distilled water is dangerous. compounds can be made which are poisonous.
i had heard the vet trick before. also, silver coins were put in the milk jugs on the wagon trains to keep the milk from spoiling. it works well!