You mean "if there is a mind around to" believe "it", because all knowledge requires and entails belief, remember? And nothing can be known to exist or occur without a believing mind, including existence itself. You can't know anything without a believing mind, including your own existence.
How do YOU KNOW "salt is soluble regardless of" having "any water around to prove it" silly? YOU KNOW that in and because of your believing mind right?
Can YOU KNOW or explain anything without a believing mind silly? You have a terminal confusion called a lack of belief AKA atheism.