Alchemy

 According to this chemistry, water is 2 parts hydrogen and 1 part oxygen (H2O).  Is water not really that uniform?  After all, even looking at the water here, they have different colors, different salt content, different plant life, different fish.  So, how can water be analyzed to such a simplified form?  Othere elements are not being taken into account and how they would combine.  Does the Periodic Table of Elements not even reveal all the elements?  From what ancient age is this table of elements which taught today as Modern Science?  Who sets the standard for the amount of information allowed to seep through to the public?  .